Contra Costa County
Integrated Pest Management Advisory Committee
Annual Status Report for 2006
The County’s IPM policy was developed by the IPM Task Force and adopted by
the Board of Supervisors in November of 2002. This action was taken in
response to one of the recommendations in a report published in March, 2001 by
the County’s Public and Environmental Health Advisory Board called Pesticides
in Contra Costa County. At the time of the adoption, the Board of Supervisors
recognized that budget constraints prevented them from funding the
recommended IPM program. The Task Force was directed to focus its efforts on
objectives that could be accomplished within the County’s existing administrative
structure and financial resources.
Each year the IPM Task Force has submitted an annual status report to the
Transportation, Water and Infrastructure Committee. Last year’s annual report
provided an update showing that the use of pesticides by County Departments
had declined by 24% and use of Pesticides of Concern by County Departments
had declined by 63% during a four year period. Despite this there was public
criticism expressed regarding the lack of progress that had been made by County
departments in fully implementing the IPM Policy. There was also criticism due to
breakdowns in communication between the County and its pest control
contractors. The County’s Public and Environmental Health Advisory Board
submitted recommendations to the Transportation, Water and Infrastructure
Committee that included the hiring of either an IPM Coordinator or IPM
Consultant to strengthen the County’s IPM program.
On August 15, 2006 the Board of Supervisors accepted the Integrated Pest
Management Task Force’s 2005 Annual Report. At that time, they:
• Directed General Services to extend the contract with Orkin for one year,
utilizing IPM techniques in all County facilities, with review by the IPM
Task Force after 6 months;
• Directed General Services to begin posting notices at County Buildings
three days before the application of registered pesticides with posting to
remain up four days afterward. Exceptions are baits, pastes, and gels
used in cracks and crevasses, and those registered pesticides contained
on a list approved by the Integrated Pest Management Task Force;
• Directed the hiring of an IPM Coordinator;
• Directed the County Administrator to work with the IPM Task Force to
develop funding and employee education options, to be discussed with
Department Heads, at an upcoming Department Head Meeting;
• Requested the Transportation Water and Infrastructure Committee to
continue to monitor the activities of the Integrated Pest Management Task
As a result of the Board Actions, Jason Crapo and John Gregory from the County
Administrator’s office met with the co-chairs of the IPM Task Force; Michael Kent
from Health Services and Ed Meyer from the Department of Agriculture. Michael
Lango from General Services and Maurice Shiu from Public Works also
participated in meetings to discuss how to strengthen the County’s IPM Program.
The discussions pointed out that the IPM Task Force had no authority over
County Department activities. The policy that was originally adopted by the Board
of Supervisors called for the creation of an IPM Advisory Committee that reported
directly to the County Administrator’s office. It was agreed that formation of the
Advisory Committee with a member of the County Administrators Office chairing
the committee would strengthen and result in better coordination and
implementation of the IPM Policy.
Also discussed were options on how to best evaluate the County’s needs for an
IPM Coordinator and quickly review the effectiveness of existing Departmental
IPM policies. Creating a totally new position would be a lengthy process involving
defining the job specifications, scope of work, securing office space and
equipment, securing funding and finally recruiting. It was felt that evaluation of
existing Departmental IPM policies could be accomplished faster by hiring an
IPM consultant. This would also help examine County needs for an IPM
Coordinator. The Administrator’s Office discussed this approach with the Chair of
the Board and received approval.
• In September 2006, the County Administrator’s Office formally retired the
IPM Task Force and activated the Integrated Pest Management Advisory
Committee that had been part of the original IPM Policy adopted by the
Board. The Advisory Committee is chaired by John Gregory from the
County Administrator’s Office.
• Orkin Pest Control has implemented IPM practices at over 130 County
controlled work sites.
• Since August, with one exception, no application of pesticides has
occurred that required posting at County sites serviced by Orkin.
• The one exception was properly posted and the procedures for prior
approval were followed as previously agreed.
• The Department Heads were informed that IPM was being implemented at
all County facilities at their meeting on September 28. The need to support
employee training for acceptance of the process was emphasized.
• An RFP was issued on November 22nd seeking an IPM Consultant who
will review the County Department Programs and policies and make
recommendations for improvement.
• IPM Consultant applicant interviews are tentatively scheduled for the first
week of January.
• Continue to work with and evaluate Orkin’s implementation of the County
• Determine if other pest management contracts have been entered into by
County Departments and, if so, ensure that they are IPM based.
• Work with the IPM Consultant to ensure development of an effective and
• Amend the IPM Policy to add public representation to the Advisory
The following Status Report from each County Department has been formatted to
discuss the Department’s Mission and Objectives related to their programs that
require pesticide use. In addition the Departments were asked to provide
information on eight basic topics that would help evaluate an effective IPM
• Education, Outreach and Training
• Program Description
• Monitoring and Inspection
• Pest Management Options
• Cost/Risk Analysis
• Program Oversight
• Record Keeping
• Continuous Improvement
The goal was to provide a report that could serve two purposes. One would be to
provide the Board of Supervisors with an update on Department IPM efforts. The
second would be to provide the consultant with a document that could be used to
help expedite the review of individual Department IPM Programs.
While the formatting and topics for the following report are uniform for each
Department, there is a variation to the level of detail reflected in each report
based on how broad or narrow the Department’s area of responsibility may be.
For instance, General Services may be asked to respond to any type of insect,
weed or disease issue so their report is generically written. Public Works
primarily deals with issues related to infrastructure maintenance, fire prevention,
sight clearance and flood control so their report goes into more detail on these
issues. The Agriculture Department has specific pests of statewide and local
concern so their report discusses those specific pests.
CONTRA COSTA COUNTY GENERAL SERVICES –
LANDSCAPE INTEGRATED PEST MANAGEMENT
Our mission is to implement and manage an IPM program for all County
buildings and Service areas that are maintained by the GSD- Grounds
Department. We will promote the combined use of monitoring, physical, cultural,
biological, and chemical control methods to effectively manage pests and weeds
with minimal or no risk to humans and the environment while keeping within the
budget constraints of the GSD- Grounds Department.
The objectives of our Landscape Maintenance pest control program is to reduce
problem pest populations to an acceptable level or threshold and the amount of
high maintenance associated with these plant pest and weeds, to create a safe
environment associated with the landscape and to have and maintain an
aesthetically pleasing landscape.
EDUCATION, OUTREACH, AND TRAINING
In the GSD- Grounds Department, we have one Pesticide Specialist that is
required to have a Qualified Applicator’s Certificate - QAC issued by the
California Department of Pesticide Regulation - DPR, Licensing certification
Program, after successful completion of a series of written state examinations.
He is also required to have twenty hours of continuing education (CE), every two
years. Our Pesticide Specialist attends pesticide seminars given by industry the
Pesticide Applicators Professional Association , and other local training classes.
The Grounds Manager is required to have a Pest Control Advisor’s License
(PCA), also issued by DPR with extensive college coursework or degree in
Biological Science, in addition to a QAC. The PCA license requires 40 hours of
CE every two years. Seminars attended include the California Weed Science
Society annual conference, the California Association of Pesticide Control
Advisors annual conference, as well as the review of trade journals, magazines
and the University of California Statewide IPM Program and website.
As far as outreach to the public and county employees the GSD-Grounds
Department answers questions regarding landscape pruning, insect, weed, or
vertebrate control. We also refer inquiries to the appropriate resources - CCC
Department of Agriculture, U.C. Co-operative Extension Service, County
Mosquito and Vector Control, or the University of California at Berkeley or at
The GSD- Grounds Department is responsible for 105 County Buildings and 27
Public Works Landscape and Lighting District Service Areas. We maintain the
landscape, grounds, and parking lot areas. We also respond to any emergency
requests or hazards. Our IPM program addresses the need for control or
elimination of unwanted vegetation in our landscape, diseases and insect pests
on landscape shrubs and trees, and vertebrate pests in the landscape. (gophers,
MONITORING AND INSPECTION
When servicing a site, landscape maintenance tasks include pruning of
groundcovers, shrubs and trees, mowing and fertilizing the turf and landscape,
irrigation repair, clean up of garbage and debris, weed, insect and vertebrate
pest control as needed. Factors used to determine how to manage the site are
the location, climate, soil conditions, irrigation, safety issues, aesthetics, past
practices, and budget constraints. The Grounds Manager and Pesticide
Specialist determines the appropriate method of control if needed, after
identifying the pest issue or problem, monitoring the site, considering all the
factors involved, then treating the site. After treatment, the site is inspected and
recommendations or suggestions are made to the building manager.
PEST MANAGEMENT OPTIONS
The following control options and methods are currently being used in our
• Efficient Landscape Maintenance Practices including the use of
landscape mulch and donated wood chips in the landscape, weed fabric,
proper irrigation systems and controllers, fertilization as required by the
landscape and turf, grass recycling in large turf areas, recycling of green
waste trimmings and clippings, elimination of turf areas in favor of low
maintenance and drought tolerant landscapes. For future landscaping,
recommending that the landscape installation be planted a minimum of 18
inches away from buildings for IPM purposes.
• Preventive planting choices, using disease resistant varieties of plant
material , native plants, the right shrub or tree for the right location, when
replacing existing landscape or installing new landscape.
• Physical or manual: hand weeding, shovels, hoes, hand weed eaters.
• Mechanical discing of field areas, tractors with flail mowers to knock down
weeds in large field areas, or vacant lots, gas powered string weed eaters.
• Biological: as directed by the CCC Agriculture Department, for example
wasps released to control a specific pest such as the ash whitefly, or
beneficial insects can be purchased for release on specific problem plants.
• Cultural: mulching landscapes using donated wood chips- conserves
moisture, prevents weed germination and growth, less pre- emergent
• Pesticides: non restricted “Caution” chemicals are currently being used
for control of weeds, fruit elimination on olive and laurel trees and use of
insecticidal soaps for insects. For gopher control the department uses
traps, bait, or work is contracted to Pest Control Company.
• Educational Resources: UC IPM Online Website, CCC Agriculture
Department, seminars and classes.
From past practice and experience, it has been established that the use of pre
and post emergence herbicides in weed control has helped the Grounds
Department control the cost of maintaining the landscape, workman
compensation claims, and the weeds. Worker safety and exposure to the public
and employees is of the utmost importance, all safety precautions are taken
when applying pesticides. Areas of high concern are not sprayed and alternative
methods are used. To date there have not been any claims against the
department related to pesticide application or exposure.
The GSD-Grounds Department has had an on going IPM policy over the years,
the use of landscape fabric and plastic polyethylene sheeting, in the landscape
with a top dressing or layers of mulch. Our department has installed over 5000
cubic yards of wood chips in County landscape supplied by tree companies at no
cost. This has reduced the use of pesticides for weed control. We have
removed large turf areas and converted them to low maintenance landscaped
areas, along with retro fitting the irrigation systems to conserve water. Hand
weeding and mechanical means are still a large part of our program for weed
Non-restricted “Caution” pesticides are used for control of:
• Weeds in landscape and cracks in hardscapes
• Broadleaf weed control in turf
• Insects and plant diseases
• Fruit elimination on Olive and Laurel Trees where the fruit presents a
• Control of gophers using baits by the department or contractors
The cost of abating weeds by hand on a regular basis is labor intensive and cost
prohibitive due to our grounds charge out rates and budget constraints. In
addition the safety of our employees is of the utmost importance. The risks
involved with repetitive use of body parts - hand, wrist, arm, elbow, back, etc.
have led to workman compensation claims. With this in mind, our Grounds
Department uses a variety of ways to maintain weeds that invade our
landscapes. We incorporate hand weeding, power weed eaters, tractor flail
mowers, discing, rototilling, mulching the landscape, and herbicide weed control,
where these methods are the most appropriate and where the budget issues are
The activities of our program are supervised by the Contra Costa County
Agriculture Department, with a yearly inspection of our storage sight, equipment
used, review pesticide reports, training records, and monthly pesticide submittals.
The GSD- Grounds Department keeps records on all pesticide applications for a
minimum of two years, as required, in addition we submit monthly pesticide use
reports to the CCC Department of Agriculture.
As required by the DPR - 20-40 hours of Continuing Education for Pesticide
License holders, this would include seminars and classes, UC IPM on line-
Statewide IPM Program, CCC Agriculture Department- to answer any questions,
ID, and suggestions, literature review and research as needed. There is always
room for improvement and better and more efficient ways to get the job
Contra Costa County Public Works Department
Vegetation Management Program
It is the mission of the Vegetation Management Program to manage vegetation
within the jurisdiction of the Public Works Department for the protection of the
residents, the environment, and the property of Contra Costa County. Fire, flood,
sight obstruction hazards, and invasive species are the primary dangers this
Our department operates under the regulation of numerous agencies. Fire
protection districts have set strict guidelines for weed abatement on our
properties. The Army Corps of Engineers have developed operation and
maintenance guidelines for our flood control facilities, which we are obligated to
follow in order to prevent flooding. The State Water Quality Control Board, the
State Air Resources Control Board, the Department of Fish and Game, and a
number of other agencies also regulate our activities.
In addition to these agencies, our department also attempts to address the needs
and concerns of our residents. Taken together, this becomes a very challenging
assignment. Failure to adequately address regulatory and safety requirements
can result in costly lawsuits. To date, lawsuits related to vehicle accidents have
accounted for our greatest losses. Flooding and fire both hold the potential for
losses far in excess of any vehicle accident we have experienced.
All of our vegetation management activities must fit within the budget constraints
of our road maintenance and flood control programs. Without the infusion of
additional capital into these budgets, increasing costs for vegetation
management activities will result in an increase of our deferred maintenance, and
increased risk to our residents from the dangers discussed above. These risks
translate into potentially enormous losses should we be found liable for any of
EDUCATION, OUTREACH, AND TRAINING
All employees in the Vegetation Management Program are required to possess a
Qualified Applicator Certificate (issued by the California Department of Pesticide
Regulation after successful completion of a series of written examinations). In
addition, our Senior Technicians are required to possess a Pest Control Advisors
License (also issued by the state), which requires extensive college coursework
in addition to passing written examinations.
Each employee receives a minimum of 40 continuing education hours every two
years, meeting or exceeding all state requirements. Examples of classes our
employees attend include the Terrestrial and Aquatic Weed Schools at U.C.
Davis, and the annual California Weed Science Society Meeting. Employees also
keep up to date on issues through trade journals and review of the scientific
literature. We believe that maintaining this high level of professionalism within our
department is an important aspect in preserving the safety of our operations.
While outreach to the public is not a mandate for our agency, we do have a
limited degree of contact with the public. This can include education regarding
plant selection along roads and flood control facilities, mosquito and other vector
related issues, and discussions regarding invasive weeds. When a member of
the public requires more assistance than we are able to provide, we direct them
to the appropriate resource. These agencies include our County Agriculture
Department, U.C. Co-operative Extension, the County Mosquito Vector Control
District, and the University of California at Davis.
The Contra Costa County Public Works Department is distinguished from most
other public works departments in that we have the responsibility to maintain
roads, flood control facilities, airports, and a variety of parcels. In most counties,
these responsibilities are distributed among various agencies, special districts,
and contractors, not concentrated within one department. This concentration of
responsibility has allowed us to develop expertise specific to vegetation
management, and yet it can also lead to the perception that we are using more
herbicides than necessary.
MONITORING AND INSPECTION
When evaluating a site for the management of vegetation, a number of factors
must be taken into account. Site location, climate, economics (budget), safety,
ecology, and esthetics are all given consideration when developing a plan for the
long-term maintenance of a property.
Site location issues include accessibility, topography, and adjacent properties.
Climate includes precipitation, wind, temperature, and relative humidity.
Economics include the funds available to maintain a site, and the personnel
available to perform these maintenance activities when they need to occur.
Safety includes conditions for the public, maintenance employees, wildlife, and
any adjacent property. Ecology can include the plants, animal life, water, and
mineral resources of a property. Esthetics is difficult to quantify but consists of
the public perception of a site. A change in any one of these factors can affect
the management of a site.
The Vegetation Management Supervisor makes decisions on the method of
control for each site after consulting with the Flood Control Supervisor or Road
Maintenance Supervisor responsible for a site. The site is examined to determine
what vegetation, if any, needs to be removed. The budget and manpower
availability are examined next. Regulations set by local fire districts, the
California Department of Fish and Game, the U.S. and Cal E.P.A., the U.S. Army
Corps of Engineers, and other agencies are also consulted.
When all of these factors have been taken in to account, an appropriate method
of vegetation management is selected. After a site has been abated, it is
evaluated to determine the level of success of the method used. Adjustments are
then made, if necessary, to the method of vegetation management used at that
site in the future (see the attached Weed Control Decision Chart).
Fire Hazard: Annual weeds growing along roadside rights-of-way in Contra
Costa County are highly flammable in our hot summers. Vehicles that pull off to
the side of our rural roads can cause fires due to contact between this vegetation
and the catalytic converter under their vehicle (a very hot surface). Cigarettes
thrown from vehicles can also start fires along these areas. Glass and metal
objects in these areas can also ignite this vegetation. Many of our roads are
adjacent to open space and parks that are at substantial risk from fire (See
attached photo of a fire scorched hill from September 2006).
Flooding: Vegetation growing in flood control facilities and in our roadside
ditches can impede the flow of water through our facilities, resulting in localized
or widespread flooding. Many of our flood control facilities have Operation and
Maintenance guidelines dictating the allowable amount of vegetation. When our
facilities are no longer able to provide 100 year flood protection, property owners
must purchase flood insurance at considerable cost. This happened to a number
of residents in Pleasant Hill a few years ago. (See attached photos of levee
damage due to rodent activity and Dam Inspection Reports).
Sight Clearance: Annual weeds and perennial trees and shrubs can limit the
sight distance along roads. This has two effects. Drivers traveling on roads with
limited sight visibility tend to move closer to the centerline, increasing the risk of
head-on collisions with other vehicles. The second effect is to limit the ability to
see, “down the road.” This places pedestrians and bicyclists at added risk. It can
also prevent a driver from seeing other hazards in a timely fashion. Some weeds,
such as puncture vine, can cause immediate ‘blow-outs” of bicycle tires, which
can in turn result in substantial injury.
Noxious/Invasive Weed Control: Public rights-of-way, including roads and flood
control facilities, have been identified as major routes for the spread of noxious
and invasive weeds. Our personnel inspect our facilities for these species in
order to control the spread of these weeds into adjacent properties.
Open Space/Endangered Species Protection: Controlling and/or eradicating
invasive and noxious weeds helps to protect open space and endangered
species from the competition of alien species.
Aesthetics: The citizens of the county have an expectation that our roads will be
maintained to a level which is aesthetically pleasing, or at least isn’t unsightly.
Roads that appear to be messy result in complaints. Weedy areas tend to attract
the dumping of debris, and unmanaged vegetation becomes a collector of wind-
Economic Impact: The hazards described above can result in litigation, and
indeed we are currently in litigation for claims resulting from some of these
hazards. Some vegetation growing along the edge of pavement can reduce
pavement life by slowly breaking and growing through the pavement surface.
Litigation and reduced pavement life have an adverse impact on our
department’s ability to serve the public.
PEST MANAGEMENT OPTIONS
We have eight basic management options for the control of vegetation on county
1. Do nothing. Allow the vegetation to grow and remain as it is. There are
few sites where we can make this decision. Urbanization and the
introduction of invasive, non-native weeds make this option difficult to
2. Controlled burn. This option is generally only feasible in large open
space or park locations. Concerns about air quality and the risk of a
controlled burn escaping control make this a difficult option to utilize. We
have used this method before, but our last burn at Marsh Creek Dam
almost escaped control.
3. Grazing. As with the controlled burn option, this method is best suited for
open space locations. Concerns have been raised regarding water quality,
soil stability, and impacts on endangered species. This method has been
used at Pine Creek Detention Basin for fire abatement, and in a few flood
control basins for cattail control.
4. Till or disc weeds. This method is usually not suitable along roads or
near flood control facilities. This method can weaken engineered soils
(levees and road shoulders), and increase silt runoff. This method may not
be legal where the Alameda Whipsnake and other threatened/endangered
species are found.
5. Biological control methods. While there is a lot of research into this field,
at this time there are only a few weeds controlled using this method.
Insects have been released in this county for the control of puncture vine
and yellow starthistle with some success. We have installed raptor poles
and owl boxes in a number of our facilities for rodent control.
6. Mow. We have a number of sites where we mow weeds with tractors,
weedeaters, and walk-behind mowers. The use of this method is limited
by budget constraints and by the availability of personnel to perform this
activity in a timely fashion as determined by local fire agencies and the
public. This method increases air pollution due to exhaust from gas and
diesel powered equipment, as well as adding particulate matter to the air.
The use of hand-held and walk-behind equipment significantly increases
the likelihood of employee injury.
7. Habitat modification. This method can include the use of mulches,
planting trees or shrubs to reduce light or fuel in an area, and the use of
selected grass species to reduce the need for abatement. We have been
using this method at a number of sites along roads and flood control
channels with marginal success.
8. Use herbicides. This method has allowed our small staff to maintain a
large number of county owned and/or maintained facilities in a timely and
cost efficient manner. The materials we use are approved for use by the
U.S. E.P.A. and by Cal E.P.A. Some citizens have questioned the use of
herbicides, and this issue has become controversial.
As stated in our IPM Task Force 2003 Annual Report, and as substantiated
through the analysis of other public agencies (see attached Roadside Mowing
Cost Estimates), it costs approximately 10 times more to mow weeds along
roads than it costs to use herbicides. Costs for manual weed abatement in our
flood control facilities can exceed a factor of 15 X due to additional labor costs.
We currently incorporate manual weed abatement options (tractor mowers and
hand-held equipment) where these methods appear to be the most appropriate,
and where our current funding allows.
The validity of these estimates can be seen in the list of the best and worst
pavement conditions in the bay area (Bay Area Transportation: State of the
System 2005). Marin County, which mows weeds along their roads, has the 5th
worst road system in the Bay Area (101 out of 105 jurisdictions). Their PCI rating
of 50 places them in the Fair category, just a few points above Poor. Contra
Costa County, which sprays weeds along most roads, has a PCI rating of 85, tied
for 2nd place in the Bay Area for the best pavement conditions. Our roads are
rated as Very Good. Roads are cost-effective to maintain when their PCI rating
falls within the 75 to 85 range.
Without an infusion of additional capital, increasing costs for weed control forces
a municipality to defer preventative maintenance operations. This becomes
increasingly expensive since major road repairs cost five times that of routine
maintenance. As the condition of roads deteriorate, hazards to the traveling
public increase. This, in turn, increases our exposure to expensive lawsuits due
to negligence. This same basic premise applies to our flood control structures
and other facilities.
A roadside right-of-way mowing program would cost our department an
additional $3 million per year. An accurate estimate of the additional cost for our
flood control facilities will be difficult to determine, but will be substantial.
In addition to the increased costs and risks noted above, worker safety must be
considered. With over 100 years of employee experience applying herbicides, no
worker compensation claims have been submitted by our employees for
pesticide related exposures. We do have a substantial worker’s compensation
claims history related to the use of tractor and manual weed abatement
equipment. Common claims include back injuries, torn rotator cuffs, and
exposure to poison oak. Currently, 10% of our maintenance employees are off
work with injuries.
The Public Works Department had developed its own internal IPM Policy before
the creation of the IPM Taskforce, and the adoption of a county policy. Our
department has practiced IPM for many years. In an effort to address concerns
related to the use of herbicides by our department, our staff has reduced the use
of so-called bad actor materials by 66%, and reduced overall herbicide use by
25% since the taskforce was formed. We have done this without the infusion of
additional capital into our budget. All herbicides used by our department are
approved for use by the U.S. EPA and the California EPA. As noted by the EPA
(see attachment) the United States pesticide safety is the highest in the world.
Our department makes use of a variety of herbicides to address specific weed
infestations. The three so-called bad actor herbicides used by our department
address specific issues as follows:
• Telar is used to control Perennial Pepperweed, in invasive weed that is
not effectively controlled by other herbicides. This herbicide is also used
on weeds that have developed resistance to other herbicides.
• Weedar 64 is an aquatically approved herbicide that we use to control
Purple Loosestrife, an aggressive invasive weed that has been found in
the Walnut Creek watershed. Due to the hydrology of the area, biological
control agents (two insects) can’t be successfully utilized for this weed.
• Direx 80 DF is a pre-emergent herbicide used in our program to prevent
the development of resistance to our other herbicides. It is used in our
agricultural core area to reduce the need to spray when crops are actively
• In addition to the use of herbicides, our department contracts with the
County Agriculture Department for the control of ground squirrels along
selected roads and levees. Ground squirrels have the potential for causing
serious, and even catastrophic, damage to our facilities (see attached
photos of recent damage).
The activities of our program are supervised by the County Agriculture
Department. In addition, our aquatic herbicide applications are monitored and
analyzed by a third-party analytical lab, with results sent to the State Water
Resources Control Board. Each year, a Biological Assessment is conducted in
our flood control facilities at the end of our work season. No impacts on the
beneficial uses of our waters have been reported from our activities. We continue
to follow the Best Management Practiced included in all of our permits.
Our department keeps records on all of our herbicide applications for a minimum
of two years, as required by regulation. In addition, we send monthly use reports
to the County Agriculture Department and the Water Quality Control Board. This
activity has allowed us to document the reduction in our use of herbicides from
Continuing education, literature review, and research conducted by our staff are
all utilized in the process of continuous improvement. As new techniques,
technologies, and regulations arise, we continue to respond and make changes
to our program.
Public Works Addendum 1
Roadside Mowing Cost Estimates
The attached cost estimate for roadside mowing in our county is based on the
experience of the Marin County Public Works Department (Public Works
Addendum 2). Most of their mowing takes place in the western portion of the
county (the cooler portion). The eastern portion of their county is primarily curb
and gutter, and requires no mowing. They indicated that they are able to mow 4
miles of roadside in 1 ½ days. For this estimate, I am assuming that our crews
will be just as efficient as Marin County personnel. These cost estimates are a
best possible scenario, and may not accurately reflect what our actual costs
would be. No provision for equipment breakdown is included in this estimate. The
cost to change to a mowing program will be six and ten times more expensive
than our current weed control program (an increase of between 1.9 million and
3.2 million dollars).
Marin tried using contract mower operators, but found them to be unreliable.
There were inconsistencies in quality and/or charges for services. All mowing is
therefore done by county staff. Marin generally uses flaggers to control traffic on
each end of a road, or portion of a road being mowed. They also utilize a shadow
vehicle that travels behind the mower to help slow traffic down and prevent
I am unable to quantify the actual cost to hand abate weeds around the
guardrails (over 400), signs (over 15,000), culverts (100’s), and other structures
along our roads. With such a large inventory of structures, I would anticipate this
operation to cost somewhere between $200,000 and $400,000. The actual cost
may be considerably higher. Flaggers should be utilized when abatement occurs
to reduce the chance of accident and/or injury for our employees and the public.
In addition to the actual cost to cut weeds around these structures, there is a
question of risk and liability. Our personnel will be put at increased risk of injury if
they are going to undertake this task. Many drivers are substantially exceeding
the posted speed limit on our rural roads (Vasco, Marsh Creek, etc…), so anyone
working along the road will be exposed to possible injury. Rocks and other debris
that are thrown into the travel area may result in damage to vehicles and/or
vehicle accidents, or injury to bicyclists. We have had to pay claims for damage
to windshields in the past when we have manually cut weeds. You may wish to
consult with the Risk Management Division to gain a clearer understanding of our
overall liability exposure from these operations.
The mowers we use run on diesel fuel, and our weedeaters have 2 cycle engines
and run on mixed gas. Using this equipment will have a negative effect on air
quality (increased levels of nitrous oxide, nitrogen dioxide, formaldehyde,
benzene, sulfur dioxide, carbon monoxide, and carbon dioxide). If we stop our
weed abatement during spare the air days, we may be unable to meet the
abatement standards set by the Contra Costa County Fire Protection District.
Marin County personnel indicated that they have started fires while mowing that
escaped their control efforts, and required response by the Fire Department. This
does not happen in Marin every year. I would anticipate that we will experience
many more fires in our county due to our hotter climate. This may be another
area of concern that Risk Management should investigate.
Mowing will require a large amount of staff during the time when our major
pavement repairs occur. We will either make fewer road repairs, or else we will
require more employees. Additional personnel can certainly be used in our
Maintenance Division, but we currently lack the resources to fund these
positions. An increase in the cost to abate weeds along our roads will therefore
take funds away from our pavement maintenance activities. According to the
Metropolitan Transportation Commission, the PCI (Pavement Condition Index) of
unincorporated Contra Costa County is 85, while the PCI of Marin is 50. A PCI of
75-89 is very good, and a PCI of 45-59 is fair. I believe this information clearly
demonstrates that changing to a mowing program will result in the overall
deterioration of our county roads. (Refer to Public Works Addendum 3)
Public Works Addendum 2
Calculation of Roadside Mowing Costs
Assuming that we can average 2.66 miles of mowing per day, that 600 miles of road will
be mowed, and that three mowings per year will be required, a total of 1800 miles of
roadside mowing will be required. To accomplish this over a 4 -1/2 month period of time
will require 9 mowing crews.
Number per Day Total Cost If
needed per Using Flaggers Not
Personnel/Equipment* Cost/Day operation Flaggers Required
Laborer 700 2 $1,400 $700
EO-I 845 2 $1,690 $845
Supervisor (Average) 1200 0.33 $400 $400
Mower 750 1 $750 $750
10 Wheeler 195 1 $195 $195
Trailer 120 1 $120 $120
Crew Cab 60 1 $60
Shadow Vehicle 80 1 $80 $80
Mowing cost per day $4,695 $3,090
Total Cost to Mow 1800
Miles of Roadside** $3,177,068 $2,090,977
Total Cost to Mow 1800
Miles of Roadside
including hand weed $3,377068- $2,290,977-
abatement $3,577,068 $2,490,977
Current Appropriation for Roadside Weed
*Labor costs include all benefits and department overhead as of February 2006.
Equipment and Labor costs are for a full, 10 hour work day. The County of Marin uses
flaggers and a shadow vehicle behind the mower to prevent accidents and injuries.
**Not included in these costs are charges for hand weed abatement around guardrails,
signs, culverts, and other structures. This will cost over $200,000, and may exceed
$400,000 per year. Assumes the mowing efficiency of Marin County. This estimate
makes no provision for equipment breakdowns.
Public Works Addendum 3
Public Works Addendum 4
Protecting Residents, Structures and Environment from Floods and Fire
Walnut Creek Channel Levee Failure 2006
Boils due to rodent damage
Depth Perspective – Rodent Related Failure
2006 Levee Damage Along Walnut Creek Channel
Wildfire September 2006
Evora Road – Bay Point
Public Works Addendum 5
The effort to protect infrastructure from weed and rodent damage is a never
ending challenge. Ground squirrels are attracted to road embankments and
earthen dams and continue to reinvade those sites from surrounding areas.
Vegetation in flood control channels and spillways can impede flow and reduce
carrying capacity. The following are copies of both recent and older inspection
reports from the Department of Water Resource, Division of Safety of Dams.
They illustrate our cooperative efforts to properly maintain the infrastructure of
roads, dams and flood control channels in the County.
Contra Costa County Department of Agriculture
Integrated Pest Management (IPM) Policy
The main mission of the County Department of Agriculture is to protect and
promote agriculture and to protect the environment. The Department is involved
in pest management on three primary levels. The first level is the departments’
mandate to eradicate or control certain introduced exotic insects and diseases
that are new to California or previously not known to occur in Contra Costa
County. These insects and diseases pose a serious threat to commercial and
backyard agriculture as well as to the environment of the State and have been
designated as such by the United States Department of Agriculture (USDA)
and/or the California Department of Food and Agriculture (CDFA). The second
level of pest management focuses on the suppression or elimination of specific
invasive noxious weeds that have potential to cause serious harm to agriculture,
native environments and urban areas. These noxious weeds have also been
designated as such by USDA and/or CDFA. The third level is long-term
prevention or suppression of certain vertebrate pests that are harming or have
the potential to harm property including crops, livestock, levees that protect
agricultural land, residences and businesses; and infrastructure including roads,
railroad rights of way and domestic water storage dams.
All three levels focus on pests that are a direct threat to public health and safety,
the health of our native habitat and environment, or have the potential to cause
serious economic harm. Our pest management programs target pests while
incorporating sound biological and environmental decisions. An IPM approach is
used and techniques are selected based on their ability to provide the effective
control and/or eradication that is required by our programs while also considering
the department’s limited fiscal resources. IPM techniques include encouraging
naturally occurring biological control, introduction of new biological control
organisms that have been approved by USDA and CDFA, mechanical control,
use of alternate plant species or varieties that resist pests, adoption of cultivation,
pruning, fertilization, or irrigation practices that reduce pest problems;
modification of habitat to make it incompatible with pest development, selecting
pesticides with a lower toxicity to humans and non-target organisms and the use
of pesticides through focused application techniques.
EDUCATION, OUTREACH, AND TRAINING
Emphasis is placed on outreach and education to the general public, schools and
industry within the county and also to maintain a well trained professional staff.
In the case of noxious weeds and vertebrate pests outreach is specifically made
to private and public land stewards, providing them with the knowledge on how to
identify the pests of concern and how to implement a rapid response for control.
(The Department expended 757 hours on Public Contact in FY 05/06.)
Maintaining Knowledgeable Staff: Our permanent staff are highly trained
professionals that are required to have a bachelors degree in a biological science
discipline prior to employment. CDFA licensing is required in five disciplines.
Four of these, Environmental Monitoring and Investigation, Integrated Pest
Management, Pest Prevention and Plant Regulation and Pesticide Regulation,
are related to overall IPM practices. Our licensed departmental staff regulates
the pest control industry and agencies, such as CalTrans, school districts, and
cities that use pesticides in the county.
Biologists also obtain a Qualified Applicator License issued by the California
Department of Pesticide Regulation. Continuing education is required to
maintain these licenses. An ongoing departmental objective is to keep
permanent staff highly trained in IPM and pesticide use practices. Most of the
training is received through the CDFA, UC IPM programs, the University
Cooperative Extension Service, the California Department of Pesticide
Regulation and frequent internal training within the department. Additionally, all
staff, including seasonal employees, are required to have documented annual
pesticide safety training prior to the use of any pesticides. Besides required
training, staff attend seminars and other programs to keep abreast of the latest
information on control and pest management techniques, endangered species
concerns, IPM, pest identification, pest biology, etc.
Education and Outreach Efforts: The education of the public, businesses,
farmers, ranchers and government agency staff has been a mainstay of exotic
pest and noxious weed control for many years. It is an essential component of
our IPM program, although it is not a solution in and of itself. For example when
private landholders and public land stewards are educated about the impacts of
invasive weeds, they take an interest in surveying the lands they control. As a
result the noxious invaders can be located while populations are still small and
eradication efforts are more feasible, less costly and have less risk of impacting
public health and the environment.
The Department maintains an “on call” desk where our biologists help the
general public, businesses and agencies with the proper identification of pests.
We provide IPM information that was developed by the University of California
regarding the effective control of these pests. In addition we disseminate
information about exotic pests, noxious weeds, and vertebrate pests on
identification and on steps that can be taken to control damage or prevent their
Grower identification workshops, PowerPoint presentations to interested groups
and stakeholders and staff training are part of our outreach effort for both exotic
pest and invasive weed programs. Outreach is also conducted at schools,
garden clubs and watershed groups as well as at special events such as the
Benefits: These measures bring awareness to the threats of exotic pests and
noxious weeds. They educate about quarantine regulations and steps that can
be taken to prevent the introduction of exotic pests and noxious weeds. This
helps to achieve compliance with established quarantines on the movement of
plants and plant products and prevent their introduction in the first place.
Increased awareness also increases the chances of early detection if the pest or
weed is introduced.
Pest Exclusion Activities: Our first line of defense in protecting our county and
state from exotic pests and invasive noxious weeds is through quarantine
enforcement and exclusion activities conducted on a daily basis to prevent their
introduction. Each time we enforce quarantine regulations and with each
interception of exotic pests, the Department helps to prevent the introduction of a
pest that can damage agriculture and the environment.
(The Department expended 13,857 hours on Exclusion Activities in FY 05/06.)
Pest Detection Activities: The goal is to detect exotic pests or noxious invasive
weeds while still in small population levels that would allow eradication or
management activities to be successful. Eradication is preferred when feasible.
However, in cases where eradication cannot be accomplished, focus would be
placed on preventing the spread of the pest to other areas of the county.
(The Department expended 19,317 hours on Pest Detection Activities in FY
Noxious Weed and Vertebrate Pest Management / Eradication Activities:
The goal is to eradicate new infestations of exotic pests and noxious invasive
weeds; to manage and prevent the spread of exotic pests or noxious invasive
weeds which are already established in the county and cannot be eradicated and
to manage ground squirrel populations that threaten agriculture, structures and
public safety. Vertebrate species other than ground squirrels that threaten
agriculture and infrastructure are controlled through a cost-share contract with
USDA which provides for a USDA Wildlife Specialist to work in Contra Costa
(The Department expended 4,972 hours on Pest Management / Eradication
Activities in FY 05/06.)
MONITORING AND INSPECTION
Pest Exclusion Efforts: Inspection of incoming shipments of plant material and
seed at UPS, Fed Ex distribution centers, and nursery shipments by Department
of Agriculture staff are conducted on a daily basis. Packages are screened and
opened by biologists trained to recognize noxious weeds and exotic pests.
Seed samples, insects and exotic plant material found in shipments are sent to
the CDFA Analysis and Identification Laboratory in Sacramento. Incoming
shipments are inspected for compliance with quarantine regulations and plant
material is inspected for exotic pests. Nursery shipments are inspected for pests
including Glassy-winged Sharpshooter.
Other exclusion efforts include federal and state Weed Free Forage and Mulch
Programs and local regulations that require the cleaning of farm and fire
equipment when moved from property to property. These local regulations have
at various times been in place but are not in effect in our county at this time.
Benefits: Each interception of exotic pests or noxious weeds entering our county
has the potential to prevent the pest from becoming established here. If they
were to become established there could be major economic and/or
environmental impacts on crops and native species that could eventually lead to
the regular use of more pesticides.
(In 2005, the Department rejected 329 shipments for quarantine violations and
intercepted 98 shipments containing live exotic pests including five invasive weed
species that were entering the county.)
The majority of the pests and weeds that require the use of pesticides for control
in our county today are non-native species that have been introduced into the
county. These non-native species can often explode in population due to a lack
of the presence of natural predators in their new environment.
Pest Detection Efforts: Exotic pest traps are placed systematically in host
material throughout the county. The traps are placed and serviced on a regular
basis according to state guidelines. Trap placement and density levels are
maintained in accordance with State Science Advisory Panel recommendations
that are geared toward detection at population levels that will allow an
opportunity to eradicate exotic pest populations.
Survey work is conducted at high risk locations for exotic pests and survey work
is also conducted for noxious and invasive weed detection. Surveys to detect
noxious invasive species are a continuous process. State and county personnel
scout and survey hundreds of miles of highways and thousands of acres of
range, parkland and open space each year to find and map any new populations
of invasive species that may have become established in the county. We also
count on the eyes of other stakeholders, land stewards, ranchers, public service
employees and university professionals and volunteers. This is the benefit of
having a vigorous education and outreach program.
Benefits: Pest Detection Activities have prevented the spread and establishment
of exotic pests in Contra Costa County on numerous occasions. The county has
successfully eradicated infestations of Glassy-winged Sharpshooter, Oriental
Fruit Fly and Gypsy Moth on more than one occasion. Eradication efforts are
currently underway for the parasitic weed Japanese Dodder (Cuscuta japonica)
as the result of initial finds through our Pest Detection Program.
Had previous eradication efforts failed, our agricultural industry would be subject
to quarantines within the state and by other countries. The county residents
would have increased the use of pesticides to protect backyard fruit and
landscaping from the serious damage caused by these exotic pests. In addition,
either our woodland areas would have required treatment with pesticides or our
native woodlands could have been threatened by gypsy moth infestations similar
to those that defoliated millions of acres of forest on the East coast.
Early detection of noxious invasive weeds helps to protect and enhance the
quality and diversity of rangelands, open space, parklands and aquatic habitats
in the county by helping to prevent exotic invasive plant pests and weeds from
becoming established or spreading. Economic benefits for citizens, ranchers and
other stakeholders are realized by the pro-active prevention and detection that
leads to early control. Environmentally, the use of pesticides is reduced when
early detection and management efforts are implemented.
Noxious Weed and Vertebrate Pest Management / Eradication Activities:
All of our pest management programs require monitoring and inspection to
determine pest presence as well as pest levels that leads to the best timing for
control measures. In the case of eradication efforts, even the presence of a
single targeted noxious weed requires action, though timing is still critical for
effectiveness and may determine the particular control option that is taken.
PEST MANAGEMENT OPTIONS
Level I. - Exotic Insect Pests and Diseases
By definition “exotic pests” are those animals, plants or diseases which may be
extremely detrimental to agriculture and/or the general public if allowed to
become naturalized in California. CDFA defines “A” rated pests as “Organisms
of known economic importance subject to mandatory state (or commissioner
when acting as a state agent) enforced action involving: eradication, quarantine,
containment, rejection, or other holding action.” “Q” rated pests are” treated as a
temporary “A” pending final determination of a permanent rating.” These pests, if
found, are eradicated or are controlled to limit spread when eradication is not
Recent history shows that infestations of Mediterranean fruit fly, Mexican fruit fly,
Oriental fruit fly, Gypsy Moth, Japanese beetle and several related fruit flies have
been found and eradicated in the state. History also finds that if these exotics
are not eradicated the result is the imposition of quarantines by other states and
countries, added financial burden to the agricultural industry and an increased
demand for pesticide use by the agricultural industry and/or general public. The
exotics can also impact residential areas and California native species. Apple
Maggot fruit fly, Olive fruit fly, Walnut Husk fly, Red Imported Fire Ant and
Africanized Honey Bee are examples of exotic pests who have become
established in all or part of the California and now must be dealt with every year
by the agricultural industry as well as the general public. Sudden Oak Death is
an example of a “Q” rated disease that is in a limited number of California
counties, including Contra Costa. It is beyond the point of where eradication is
possible and an extensive quarantine has been placed on infested counties by
the other states and countries in an effort to protect non-infested areas by
containing the disease within its current range.
In order to prevent the introduction of A and Q rated pests into the state, the
California Dept. of Agriculture (CDFA) has specific guidelines for each pest and
contracts with the county to monitor for their arrival. Contra Costa employs 16
Pest Detection Specialists who spend eight months a year trapping for exotic
insect pests. According to protocol they place, inspect and relocate the traps in
their specific districts throughout the county. During their tenure they deal
extensively with homeowners and nurseries, educating the public about the
program. In the height of the season over 12,000 traps are serviced each month.
If one of the targeted insects is found it sets into motion a specific delimitation
response protocol. Large numbers of pheromone traps are set out in patterns
dictated by the CDFA procedure manual to determine how widespread the
infestation has become. There are action levels in the protocol which indicate
when an eradication process must be set in place. Finding different life stages,
trapping multiple adults within a confined area or a mated female with viable
eggs will generally require an eradication response.
The eradication response is also well defined by CDFA and USDA. For example,
a Mediterranean fruit fly eradication program may involve fruit removal and
ground spraying at the epicenter of the find if properties containing fruit with larva
are discovered. Generally, aerial spraying to eradicate Mediterranean fruit fly is
no longer used in urban areas. A sterile Mediterranean fruit fly release program
has been developed and is used as long as the sterile fly rearing facilities can
produce adequate numbers of sterile flies to address the situation. There are a
couple USDA rearing facilities used to produce large numbers of fruit flies that
are treated in the pupa stage by radiation rendering them sterile. These flies are
then released by the millions to mate with wild flies. This results in the wild
female laying sterile eggs. After 3 life cycles have passed with no further finds of
wild target flies, the insect is declared eradicated. Though each individualized
response may be very expensive, taking no action results in even costlier long
term impacts on agriculture and the environment.
Aside from the targeted A and Q rated organisms, there are those that are given
a “B”-rated designation. These are insects that do exist in the state but which can
be devastating to a particular segment of agriculture and are of limited
distribution. The Glassy-Winged Sharpshooter (GWSS) is an example of a B
rated insect whose populations rose exponentially and became a threat to the
grape industry due to it being an efficient vector for Pierce’s Disease. CDFA
developed a survey protocol for delimitation and eradication of this insect. Most
counties in California work under a state contract that is federal, state and
industry financed. Our 16 detection staff place GWSS traps at the rate of 5 per
square mile throughout the urban areas of the county. Three other permanent-
Intermittent staff inspect all incoming nursery shipments from infested Southern
California counties. In addition to the urban traps, GWSS traps are placed in
vineyards and nurseries to detect incipient infestations of GWSS. A delimitation
is triggered on a find of GWSS in a trap and 5 adults found in a 5 day period
trigger an eradication effort that involves spraying of vegetation and soil
treatment with an approved systemic pesticide. Eradication may be very
expensive but inaction could result in the spread of Pierce’s Disease killing
thousands of acres of grape vines. The need for public education is paramount
because this insect is most often found only after is has become established in
urban areas. A stingless wasp that parasitizes the egg masses of the GWSS has
been released by CDFA in the hope that eventually the wasp will control existing
populations. Our county had a GWSS infestation in Brentwood that our
department was successful in eradicating. We have also successfully eradicated
new introductions of GWSS that have arrived with nursery stock to nurseries and
newly landscaped areas around the county.
Level II. - Noxious Weed Eradication/Management
“A” and “Q” rated Noxious Weeds: In California “A” rated weeds are generally
not known to occur in the state or are known to occur in small populations of
limited distribution. “Q” rated weeds are new introductions into California that are
felt to have a high potential for economic or environmental harm and have not yet
been otherwise rated by CDFA. Actions on “Q” rated weeds are the same as on
those that have been “A” rated. There are 44 “A” rated weeds listed by the state
of California. Our objective is to exclude, search for, locate and eradicate “A” and
“Q” rated weed populations that may invade Contra Costa County.
Many “A” rated noxious weeds have documented negative effects on:
• Rangeland productivity, livestock nutrition and property value; In some
cases the cost of control of noxious weeds once they become established
exceeds the value of the land for grazing or other uses.
• The health of livestock; when consumed in large quantities many noxious
weeds cause sickness and even death.
• Agricultural crops.
• Roadside vegetation management for sight and fire problems.
• Park and open space for recreational values.
• Species diversity and wildlife including endangered species habitat in
• Soil moisture, native plant communities and watershed capacity.
• The navigability of waterways.
• The use of water for recreation and drinking.
• Aquatic habitat biodiversity and productivity often creating anoxic and
abiotic-aphotic zones in the water column and benthos.
Exclusion, Quarantine and Prevention efforts are the first line of defense in
protecting our county and state from invasive noxious plant species.
Surveys for and early detection of noxious invasive species are a continuous
process. State and county personnel scout and survey hundreds of miles of
highways and thousands of acres of range, parkland and open space each year
to find and map any new populations of invasive species that may have become
established in the county. We also count on the eyes of other stakeholders, land
stewards, ranchers, public service employees and university professionals and
volunteers. This is more effective with a vigorous education and outreach
These measures will enhance the quality and diversity of rangelands, open
space, parklands and aquatic habitats in the county by protecting them from
exotic invasive plant species known to cause economic and environmental
damage. Economic benefits for citizens, ranchers and other stakeholders will be
realized by the pro-active control of these major noxious weed pests that
threaten animal forage and agricultural productivity, and increased weed
management costs. Watershed values will be enhanced and waterways can
remain navigable. Wildlife habitat and biodiversity will face a reduced threat from
exotic invasive species.
When “A” or “Q” rated weeds are found a series of procedures take place
including delimitation, further education and outreach, and eradication as
mandated by state guidelines.
Delimitation is the process of finding out through survey where and how many
acres/locations of the pest exist. State and or county staff may walk creeks,
drive along state highways and county roads, contact land stewards and
ranchers, and contact university and college professionals to gather information
on the extent and possible locations of the infestation. GPS readings may be
taken in this process. This assessment of the problem helps coordinate
Quarantines: may be imposed in an attempt to keep the noxious weed from
spreading elsewhere in the state or county.
Eradication Techniques: As defined by CDFA eradication is the complete
elimination of the weed from the target area. Eradication is applicable mainly to
newly-invading weeds that are confined to a limited number of small areas.
Techniques may include one or more of the traditional IPM methods including
mechanical removal, prescribed burns, habitat modification, controlled grazing,
mowing and the use of herbicides. Specific methods would depend on the
propagative and life cycle characteristics of the particular noxious weed.
Treatments may be carried out by the County Department of Agriculture as
directed by CDFA.
The following are control options for rated noxious weeds have been utilized by
the California Department of Food and Agriculture and our department:
• Chemical control is the method of choice for the eradication of most “A”
rated weeds because of the effectiveness, cost and ease of use. This
option provides for a quick kill to prevent the spread of the noxious weed.
The specific chemical and method of treatment will depend on the specific
noxious weed, its location and characteristics.
When pesticides are used it is only after careful consideration as to
feasibility where other management methods are ruled out or where they
are used in conjunction with other management techniques. Consultation
is made with University of California Statewide IPM Program (UC IPM),
the University of California Cooperative Extension Service, CDFA, and the
California Department of Pesticide Regulation. Only federal and state
EPA registered products are considered and all use requirements are
followed. Products used in our programs have no or minimal impact on
human health, the environment, and non-target organisms when used
correctly and as intended.
• Mechanical or hand grubbing has been used in environmentally
sensitive areas such as areas where drinking water or endangered
species may be affected. Hand grubbing and mechanical control is
generally only effective on very small populations of noxious weeds that
do not have deep roots or rhizomes.
• Mechanical harvesting for the control of aquatic weeds is conducted
under some circumstances, with the harvested plant material disposed to
land. It should be noted that mechanical harvesting results in a
disturbance of the aquatic habitat. Further, it has an indiscriminate
deleterious impact on non-target aquatic animals and can result in a major
physical disruption to the water body. Mechanical harvesting also
exacerbates the spread of some aquatic noxious weeds. Generally
mechanical harvesting would be used and has been used for the
eradication of certain aquatic weeds such as hydrilla as part of an
integrated eradication program to eliminate all life cycles of a noxious
• Biological control generally involves many years of searching and
testing is rarely compatible with an eradication project. Classical
Biological control is the importation and release of natural enemies or
grazers (host specific insects, arthropods or in some cases fish) that feed
on the noxious weed in its native land. These are usually flies, beetles or
moths that feed on the leaves, roots or seeds of the weed, reducing the
overall population. Biological controls also have the advantage of being
non-toxic and are able to reduce the population in types of situations
where other methods would be impossible. They are the tool of choice in
areas such as wilderness areas and huge tracts of marginally productive
land where chemical or mechanical control would be impractical or the
cost would be prohibitive. In some cases plant pathogens, or diseases,
usually fungal that attack noxious weeds and negatively effect its growth
and reproductive potential are utilized. One species of fish has been
imported and used for the eradication of hydrilla, an aquatic weed. The
fish eggs are treated to render the offspring sterile.
Current projects in Contra Costa County involving A & Q rated noxious
Japanese Dodder (Cuscuta japonica): This is the only known “A” rated weed in
the county. It was first found by one of our detection staff in 2005. Extensive
outreach through the press and detection surveys done by our department
resulted in a total of seven infestations found to date on nine properties in
residential and riparian areas. This is a parasitic weed that has the potential of
completely overtaking and destroying a very wide variety of native and
ornamental plants. It has been found on California Live Oak, willow, California
buckeye, elderberry, apple, plum, and citrus as well as over 30 ornamental trees,
shrubs and vines.
Mechanical: Complete removal of infested host plants using chain saws
and hand tools is the preferred eradication method. It is the method that
our department has used on all nine properties. Infested plant material
that is removed is disposed of in a controlled way at one of the land fills in
Biological: There are no effective biological control methods.
Chemical: Glyphosate was used on one property in Yolo County without
success. Triclopyr to kill the host plant was also used on one property in
another county. This is not a feasible control method because of the
unsightly affect that dead plants would create in a landscape situation and
because of the physical hazards that would be created by falling branches
and tripping hazards.
Red Sesbania (Sesbania punicea): Red Sesbania is a “Q” rated noxious weed.
The only known infestation in the wild areas of the county was found by our staff
in the riparian area of Kirker Creek. Eradication efforts commenced in 2006
involving mechanical removal using chain saws followed by focused stump
treatment. It also involved hand pulling of seedlings. Eighty-eight of these small
trees were cut and stump treated (74 with triclopyr/oil and 14 with 50%
glyphosate) and 804 seedlings were hand pulled so far this year. Seed pods
were also hand collected to reduce the seed bank reservoir with the help of
volunteers from a local school. The seed is expected to have a viability of up to
Mechanical: Hand pulling of seedlings is an effective control method
because of the single taproot. This is the preferred method by the
department at this time though it is more labor intensive than chemical
spot treatment. It is only feasible due to the limited size of the infestation.
It is being performed as an experimental project. Depletion of the seed
bank may take up to 30 years due to the longevity of the seed.
Biological: There are no effective biological control methods.
Grazing: This method is impractical due to the location of the infestation.
Chemical: Triclopyr and glyphosate provide effective control of red
sesbania. We decided to use these materials only in the initial treatment
of larger diameter established plants as stump treatment. This treatment
delivery is more focused than foliar spray and was a compatible method
with what we were trying to accomplish in using hand pulling as the main
method of eradication. Mechanical removal involved the use of a chain
saw followed by stump treatment of a 50/50 mixture of triclopyr and oil or
50% mix of glyphosate. We do not anticipate the need for any future
chemical use if our experiment with hand pulling is successful.
Current projects in Contra Costa County involving B rated noxious weeds
Identified as Being of Local Importance:
Artichoke Thistle (Cynara cardunculus): Artichoke thistle is a highly invasive
non-native perennial weed species that displaces herbaceous plants and annual
grasses, decreasing the production value of agricultural land. The stout, upright
yet spreading nature of the plant, its formidable spines, and high densities make
wildlife and livestock movement through it difficult. Mature plants can produce
hundreds of seeds, which will remain viable in the soil for fifteen years or more.
Contra Costa County was identified as one of the most heavily infested counties
within the state with 100,000 acres of land affected at the inception of the
departments’ pest management program in 1979. It has been eradicated from
many properties and has been reduced to a very few scattered plants on most
other properties that have been treated over the years. There remain some
areas in the county that the department has not yet been able to start treatment
due to limited resources. East Bay Regional Park District, Mount Diablo State
Park, many of our cities and our ranchers have partnered with us both financially
and with resources over the years.
Mechanical: The typically large size and spiny nature of artichoke thistle
plants make physical removal very challenging. It has a deep perennial
taproot, capable of vigorously regenerating unless the entire root system
is destroyed. Removing the deep tap root system from hard clay soils is
nearly an impossible task for an individual plant, let alone for the tens of
thousands of plants that occur in the county. This method may be used
on individual plants under special circumstances such as a plant that
invades a certified organic farm or ranch.
Biological: There have been no efforts to develop biological control
agents for artichoke thistle due to its close relation to the commercial
Prescribed Burning: Prescribed burning for artichoke thistle is not an
effective control method. Fire may remove some top growth and possibly
kill some seed on the soil surface. However, artichoke thistle has been
observed to be one of the first colonizers to arrive following wildfire.
Grazing: Conventional grazing by sheep or cattle will not control
artichoke thistle and in fact can promote it, because grazing animals
usually avoid this plant and selectively feed on species that would
otherwise compete with it.
Chemical: Glyphosate, dicamba, clopyralid and 2,4-D are all effective
herbicides for controlling artichoke thistle and all are recommended control
methods by UC Cooperative Extension Service Weed Research &
Information Center and CDFA. Glyphosate is non-selective and will kill
the forage grasses as well as the targeted weed species. Dicamba,
clopyralid and are more effective than glyphosate or 2,4-D and are used
during the spring and early summer when annual grasses are still green
and actively growing. 2,4-D is generally not used by the department on
artichoke thistle because of its lesser efficacy on this plant. However, it is
sometimes used early in the season where there is a mix of artichoke
thistle with purple starthistle. In this case the purple starthistle is the
primary target. Glyphosate is used in some sensitive areas, such as to
treat individual plants within an orchard or plants immediately adjacent to
a wetland area, where other herbicides may have harmful effects.
Glyphosate is used is used in a narrow window late in the season after
annual grasses have dried but before the artichoke thistle set seed.
Purple Starthistle (Centaurea calcitrapa): Purple starthistle is a highly invasive
non-native biennial weed species that displaces annual grasses and decreases
the production value of agricultural land. Its formidable spines and high densities
can be an impenetrable barrier to the movement of wildlife and livestock in open
rangeland areas as well as to horses and hikers in parkland areas.
The occurrence of purple starthistle infestations in Contra Costa County is not as
widespread as artichoke thistle infestations. However, being a prolific seed
producer, it has the potential to become as large scale a problem as artichoke
thistle. Early identification and eradication of isolated populations is key to
preventing its establishment in non-infested agricultural lands. We have the
same partners in our control and eradication efforts on this noxious weed as with
Mechanical: Mowing is not an effective method of control for purple
starthistle. The rosettes are too low to be cut and plants that have already
bolted often respond to mowing by producing multiple rosettes. Mowing
plants that have begun to flower will spread the cut flower heads, which
may still be capable of dropping mature seed.
Biological: There are no effective biological control methods for purple
Grazing: Like artichoke thistle, conventional grazing by sheep or cattle
will not control purple starthistle and in fact promote it, because grazing
animals usually avoid this plant and selectively feed on species that would
otherwise compete with it.
Chemical: Clopyralid, 2,4-D and dicamba provide effective control of
purple starthistle but have little or no effect on grasses and are
recommended by CDFA. Purple starthistle and artichoke thistle
infestations occur in similar habitats throughout Contra Costa County.
Populations of these agricultural pests often overlap and the control
methods are essentially identical. The pest control practices of these two
noxious weed species are often performed simultaneously. 2,4-D is used
as a part of our spray mix when the plant is in its rosette stage prior to
bolting. 2,4-D is highly effective at this stage and is a very inexpensive
when compared to clopyralid and dicamba. The low expense of this
material helps us to use our fiscal resources more wisely. Glyphosate
may be used late in the season after rangeland grasses have dried.
Purple Loosestrife (Lythrum salicaria): Purple Loosestrife was first detected in
the Walnut Creek watershed in 2003. It is an extremely serious pest in parts of
the Midwest and has been found in isolated areas of the northern Sacramento
Delta and southern San Joaquin River. It has the potential of destroying the
riparian environment. Each plant can produce over one million seeds in a
season. The infestation in Contra Costa County extends over 12 linear river
miles. This eradication effort involves surveys for detection, GPS mapping and
spot spraying of individual plants.
Mechanical: Not effective due to extensive seed banks and difficulty in
removing propagative root mats of this plant.
Biological: A leaf eating beetle that shows some promise in areas that
are not or cannot be treated with herbicides. This is not compatible for
use in areas where eradication is the goal such as what we have in Contra
Grazing: This is not an option for this pest due to the riparian habitat
where it is found.
Chemical: The primary consideration here is the proximity of purple
loosestrife to creeks in the riparian areas. Chemical options are limited.
Glyphosate is legal to use but has been found to be of limited
effectiveness. Imazapyr is also legal and has been used for the first time
by our staff this season. Effectiveness is still under evaluation by our
department. Both chemicals have been recommended by CDFA and
have been reported as effective in other areas of the state.
Kangaroo Thorn (Acacia paradoxa): There is only one known site of a little
less than one net acre in the county. It is located in our coastal range adjacent to
large open space parkland area. An eradication project was started on this
noxious weed in 2005. The first year involved mechanical removal using chain
saws followed by focused stump treatment. This year and in subsequent years
control will be by hand pulling of seedlings.
Mechanical: Hand pulling of seedlings is an effective control method
because of the singe taproot. This is the preferred method by the
department and is feasible due to the small size of the infestation area,
though this method is more labor intensive than chemical spot treatment.
It is expected that depletion of the seed bank may take over 20 years due
to the longevity of the seed.
Biological: There are no effective biological control methods for
Grazing: This method is impractical due to the location of the infestation.
Chemical: Triclopyr provides effective control of kangaroo thorn. The
initial treatment of established mature plants involved mechanically cutting
the plant at its base using a chain saw followed by stump treatment with a
50/50 mixture of triclopyr and oil.
Smooth Distaff Thistle (Carthamus baeticus): This is also a very small
infestation found by our staff in 2005 in a remote open rangeland area of the
county and is the only known site in the county. This is an annual plant that
starts from a rosette. The site has been chemically spot treated followed by hand
removal of missed plants later in the season.
Mechanical: Hand pulling of mature plants prior to maturation of seed is
an option that we have used on plants that have been missed during
earlier chemical treatment.
Biological: There are no effective biological control methods.
Grazing: Plants are avoided by livestock.
Chemical: dicamba provides effective control and is the material of
choice by the department.
Oblong Spurge (Euphoria oblongata): This noxious weed is somewhat
prevalent in areas of our coast range. It can take over meadows and open
areas. The department has treated it since 2001 in the Alhambra Creek
watershed and has treated small isolated “leading edge” populations in three
other areas in the county including one small site on Mount Diablo.
Mechanical: Mowing is not an effective control method. Hand pulling at
the right time of year if in looser soils can be effective in small areas.
Otherwise the perennial root system is difficult to remove effectively.
Biological: There are no effective biological control methods.
Grazing: This plant is toxic to livestock.
Chemical: Clopyralid, dicamba and triclopyr provide effective control of
oblong spurge while having little or no effect on grasses. Glyphosate is
also effective. All are used in our program depending on maturity of the
Perrennial Pepperweed (Lepidium latifolium): This weed is extremely
invasive. It was originally found in the northern portions of the county on the rim
of the bay and delta. It is now in many of our dry land and open areas and is
invading rangeland. If left unchecked it may become the single worst noxious
weed in the county as it has become in some other parts of California.
Unfortunately our resources are too limited to tackle the extent of this weed as it
already covers an estimated 5,000 net acres. We are attempting to control
isolated populations and have applied for grants in an attempt to do more control
of this weed at least to stop the leading edge.
Mechanical: Not effective due to extensive perennial rhizomes.
Biological: There are no effective biological control methods.
Grazing: Not effective.
Chemical: Chlorsufuron is the most effective material and is
recommended by UC Cooperative Extension Invasive Weed Research &
Information Center and CDFA. It is used as the first line of defense by
Weed Management Area groups in other counties in the state where this
noxious weed is targeted. Glyphosate on freshly mowed perennial
pepperweed can be effective, however this method is too labor intensive
and our department does not have the mowing equipment. Dicamba
provides limited control.
Russian Knapweed (Acroptilon repens): This noxious weed has been found in
three small areas of the county. It is a perennial that has caused extensive
damage in other areas of the State in which it has been found. It was first treated
by our department three years ago and all three populations appear to have
completely been eradicated.
Mechanical: Not effective due to extensive perennial rhizomes. This
method was tried by our department on the smallest infestation site in the
county but was found to be ineffective due to extensive resprouting from
roots that remained in the soil.
Biological: There are no effective biological control methods.
Grazing: Not effective.
Chemical: Dicamba is the most effective material to use on Russian
Knapweed and is the method of control used by our department.
White Horsenettle (Solanum elaeagnifolium): This noxious weed has been
found by our staff in a few small isolated areas of the county. It grows very
dense. Because of its rhizomes and seed production it becomes very difficult to
control resulting in taking productive land out of use. Natural spread is very slow.
We are attempting to eradicate the few populations that we have of this noxious
Mechanical: This was tried by our department on a very small infestation
and was found to be not effective due to resprouting from perennial
horizontal roots and root fragments.
Biological: There are no effective biological control methods.
Grazing: This plant is poisonous to livestock with the possible exception
of goats. However up to 10% of ingested seed will pass through the goats
digestive tract resulting in spread of the infestation.
Chemical: Dicamba, triclopyr and chlorsulfuron provides effective control.
Glyphosate may be used late in the season just before seed production.
Barb Goatgrass (Aegilops triancialis): Limited populations of this pest have
been found at five sites in the county. One is located in East Bay Municipal
Water District owned watershed property and is treated by EBMUD using
glyphosate. Another site is at Parks Reserve Force Training Area (US Army)
where prescribed burns have been used as a control method. This is an annual
grass that is mostly spread by seed that sticks to the coats of livestock. It can
displace all other native and non native plants in open rangeland settings. The
seed is not long lived.
Mechanical: This method is utilized by the department on one very small
infestation site in the county. The site was originally scattered over a
5’X40’ area. After three years of hand pulling before seed set this site has
been reduced to 20% of what it was the first year. This method is highly
time consuming and would not be feasible on a site any larger than the
one that we have used it on.
Biological: There are no effective biological control methods.
Grazing: Livestock avoid this plant.
Prescribed Burn: This is an effective method as long as there is enough
plant material to provide a hot burn. It must be done after the plants dry
and before the seed can be dispersed by animals. There is significant
danger of the fire going out of control and therefore it involves utilization of
Chemical: glyphosate is the most effective material and is used by our
department on this weed.
Hoary Cress (Cardaria draba and Cardaria chalepensis): These two closely
related noxious weeds, heart-podded and lens-podded hoary cresses, are found
in a few small populations in the county. These plants have very vigorous roots
and are prolific in sprouting from the roots. The populations spread slowly
naturally but spread very rapidly when disked. Dense populations take
productive land out of use.
Mechanical: Hand pulling and other mechanical methods are not
effective due to vigorous resprouting from perennial rhizomes.
Biological: There are no effective biological control methods.
Grazing: This plant is poisonous to livestock.
Chemical: Dicamba and chlorsulfuron provides effective control as
recommended by CDFA.
Pampas/Jabata Grass (Cortaderia selloana & Cortaderia jubata): These
closely related plants are poised to invade our open and native habitats in central
and East County. They have already done so in West County beyond our
resources to try to control. We recognize the potential of this noxious weed to
infest open dry land areas of the county. Our program involves treatment of
leading edge pampas and jubata grass on CalTrans right of way that is acting as
a pathway for intrusion of this plant from the western area of our county.
Mechanical: Mechanical removal is effective but is very time consuming
due to the size of the mature plant. When the plants are located on steep
banks, mechanical removal becomes hazardous if not impossible.
Biological: There are no effective biological control methods.
Grazing: This method is not practical due to the location of the plants.
Chemical: Imazapyr is the most effective material and is the material
most used by the department. Glyphosate provides limited control.
Level III. - Vertebrate Control and Management Program
Depredating Vertebrate Pests
Complaints: The objective is to recommend control measures within 24 hours of
receiving the request for information. All depredating animal complaints within an
agricultural setting are referred to the USDA Wildlife Specialist trapper in writing
and faxed to the appropriate number.
It is our policy to give advice on control of wildlife pests such as raccoons, bats,
opossums, etc. We consult the Vertebrate Pest Control Handbook put out by
CDFA and other U.C. publications for control options. The local Fish and Game
Department can assist with answering questions regarding game species. We
also recommend pest control operators that perform exclusion, removal and/or
Ground Squirrel Program
The objective of our program is to minimize agricultural and other economic
damage caused by ground squirrels by applying the appropriate control
techniques under cooperative agreement with persons/agencies requesting
Damage from ground squirrels includes crop loss, burrowing that can undermine
delta levees, railroad tracks and domestic water impoundments; wildlife
depredation and human health potential harm through the vectoring of a number
of transmittable diseases.
The unique life cycle and behavior of the ground squirrel heavily influence the
selection of control procedures. There are a few steps involved before control is
• Verification that ground squirrels have been correctly identified as the pest
causing the problem.
• Survey of the habitat.
• Confirm the type of damage that is occurring or expected.
• Evaluate whether the control zone is an environmentally sensitive area.
• Are there ground squirrels on adjacent properties that will reinvade the
• What is the best available control option or combination of options that will
effectively handle ground squirrel management at the site?
Management strategies can be defined as the overall control plan for the pest
situation. Varied management strategies for ground squirrels are possible,
depending on the problem, the situation and the desired objectives. It is much
easier, less expensive, and less time consuming to control a population before
there is extensive damage.
Many control methods are effective against ground squirrels only at certain times
of the year. Knowledge of the life cycle of the ground squirrel is an essential
component to initiating control measures. The exact dates of changes within the
life cycle will depend on the region, year, weather conditions etc. Some shooting
of squirrels may be necessary to determine this in a particular area.
In colder regions, ground squirrels hibernate during the winter. This is not the
best time to initiate control. Fumigants used at this time will not give desired
control as the hibernating squirrel generally will not receive a fatal dose due to
decreased respiration and that the burrow may be plugged behind them. Those
squirrels that are active above ground at this time feed chiefly on green herbage.
Vitamin K in the green foliage acts as an antidote to anticoagulant baits making
them ineffective during the winter and spring.
Ground squirrels emerge during late winter, early spring. This is when breeding
takes place. This is the season when fumigation will be most effective. There is
moisture in the ground to hold the fumigant and the young have not yet emerged.
During late spring/early summer the ground squirrels diet normally switches from
green herbage to seeds and nuts. A treated bait program is most effective when
the diet has shifted to a primarily seed diet and all ground squirrels are active
Ground squirrels are active until the hotter summer months, when there is a
period of inactivity known as estivation. The young of the year, as well as ground
squirrels along coastal areas, probably won’t estivate. A control program will not
be effective if some of the squirrels are estivating, so controls should take place
either prior to or after estivation.
Ground squirrels will emerge as the summer-early fall temperatures cool. Later,
adverse environmental conditions will decrease activity during fall and induce
Certain settings require different materials and methods. For example, on
rangeland the objective may be to reduce the squirrel population to 10 to 20% of
the carrying capacity and to keep it at about that level. In this instance, hand
baiting with zinc phosphide oat groat bait is a strategy used by some counties
though poor bait acceptance of zinc phosphide due to the “garlic” odor of the
toxicant has been reported in some areas. Zinc phosphide bait is not used by
our department because of its acute toxicity to humans and difficulties with bait
Available Management Options:
• Anticoagulant baits are very effective when used properly in the right
season. They are commonly used for ground squirrel control. There are
two types of anticoagulants, Diphacinone and Chlorophacinone, that our
department may use. Both are very similar in their properties and
effectiveness. Both diaphacinone and chlorophacinone are used at very
low concentrations (.005% or .01%) on rolled oat groats. The rolling of the
grain along with dying the bait a blue color makes it much less acceptable
to non-target animals. To essentially eliminate non-target concerns the
.01% bait is used as a broadcast at a rate of 2 to 3 grains per square foot
in open land areas. The .005% bait is used in bait stations. Bait stations
present a greater risk of non-target take than bait that is properly
broadcast. This is due to spillage from the station if it is not properly
secured which in turn would allow non-target species to gain access to the
bait. In addition, having a large volume of material located in one location
would potentially create a hazard by allowing the ground squirrel to gorge
themselves and thus have a high concentration of toxicant within its body.
Canine species that scavenge on the ground squirrel carcass would be
exposed to this high concentration of material which in turn may create a
secondary poisoning. Ground squirrels that feed upon broadcasted bait
consume a much smaller amount of the material and thus pose a minimal
problem for secondary poisoning concerns. The use of anticoagulant
baits is cost effective when compared to most other control methods.
Generally the use of broadcast anticoagulant baits is the preferred control
method used by our department.
• Fumigation. Ground squirrels can be controlled in their burrows by
several types of toxic gases, one of which requires a restricted materials
permit from the local county agricultural commissioner. Fumigation is
most effective in the spring or at other times when soil moisture is high. At
those times, gas is contained within the burrow system and does not
diffuse into small cracks that are often present in dry soil. Fumigation is
not effective during periods of hibernation or aestivation because the
squirrel plugs its burrow with soil. Plugs are not obvious when examining
the burrow entrance. The USDA produces a relatively safe and easy-to-
use smoke/gas cartridge for fumigating burrowing rodents. The cartridge
is a mixture of chemicals that, when ignited, produces a suffocating
carbon monoxide gas. Cartridges are available at county agricultural
commissioners’ offices and can be used without a permit. Smoke
cartridges may cause a fire threat if not used during the appropriate time
Aluminum phosphide is another fumigant that is registered for controlling
ground squirrels. A restricted material permit is required for the certified
applicator to purchase and use aluminum phosphide. Moisture in the
ambient air and soil activates the solid tablet to form a toxic vapor. Two to
four tablets are used per burrow. A crumpled piece of paper must be used
to plug the hole prior to sealing it with soil. This prevents the tablets from
being smothered after sealing of the burrow entrance.
There are special Threatened and Endangered Species concerns to be
considered with the use of fumigants. For example, inactive burrows can
be used by Tiger Salamander and Burrowing Owls. Use of fumigants is
prohibited in burrows that are inactive. An abandoned burrow will
generally have cobwebs, leaf litter or other debris. Whitewash material
(from bird droppings) around the opening would also be an indication that
the burrow should not be treated.
• Trapping is practical when squirrel numbers are low to moderate and
encompass a small area. Trapping also serves as a method to use when
baiting is not effective. Live-cage traps are not recommended because
they present the problem of how to dispose of the live animals. Because
ground squirrels carry diseases and are agricultural pests, the California
Fish and Game Code specifies that it is illegal to release them elsewhere
without a written permit. Conibear size 110 kill traps are used in ground
squirrel control. Pre-filling all burrow openings with soil prior to trapping
will assist in identifying active from inactive burrows and make early
trapping much more decisive, requiring fewer traps. Only reopened
burrows should be trapped. Trapping is very time consuming and is
generally not used by our department.
• Habitat Modification can make an area less favorable for ground
squirrels. Remove junk piles, pruning stacks, rock piles, and old
equipment. These areas act has harborage. Another method of habitat
modification in recent studies indicates that destroying the burrow systems
after a control program detracts squirrel re-invasion of the area. Shallow
roto-tilling is ineffective. The tractor should be equipped with a rippage
blade 18 inches in depth. Repeated disking or plowing of a squirrel-
infested area will discourage the animals and they will move to the
margins of the field along the fencerows, ditches or road right-of-ways.
Flood irrigation of orchards and field crops will also discourage ground
squirrels. This method of cultural practice reduces the carrying capacity
but does not eliminate the squirrels. It is not practical in many situations.
• Behavioral Modification can sometimes be achieved with the use of
seed protectants and chemical repellents are means of behavioral
modification which are effective for some species but are rarely a solution
to ground squirrel problems. Sound and visual repellents are ineffective.
• Exclusion can be used in some situations through squirrel-proofing
buildings and by using tree bands and trunk protectors. Fencing is not
considered a practical solution because ground squirrels are good diggers
and excellent climbers. Some innovative electrified fences have provided
partial relief by protecting small plots for a growing season.
• Predators such as coyotes, foxes, bobcats, badgers, hawks, eagles,
rattlesnakes, and gopher snakes, eat ground squirrels and can be
beneficial in reducing ground squirrel numbers to a point. The use of
artificial perches and nests may be used to enhance raptor use of an area.
This however, does not guarantee that the raptor will prey upon the target
population. Predators are generally not effective in controlling squirrels to
• Shooting is a practical way of determining life cycle stages and litter sizes
in a particular year. Small populations may be controlled by shooting
where it is legal or may be used in conjunction with other control methods.
Shooting is not a feasible control option due to labor costs, the high cost of
ammunition and the limited number of squirrels taken in areas where
populations are high.
Ground squirrel control is usually not a one-time procedure. Continue to monitor
the site for reinfestation. Since ground squirrels are fair-weather, day-feeding
rodents, observe the site during daylight hours when they would be most active.
Threatened and Endangered Species
The presence of a threatened or endangered species can have a significant
impact on ground squirrel control, depending on the species being protected. In
most instances, at least one of the three major control options remains a viable
method. Where options are limited, special efforts as to the precise timing of
control and the use of the best materials and equipment used by well trained
applicators becomes essential in order to maximize control results. Federal
guidelines and restrictions have been established with the use of baits and
fumigants. The California Department of Pesticide Regulation web-site is
consulted for use restrictions.
In summary the departments’ ground squirrel program may involve the use of the
following control materials in the order of likely use:
Anticoagulant baits by broadcast
Anticoagulant baits in bait stations
Rarely used alternatives:
Phostoxin (aluminum phosphide)
Conibear No. 110
Havaheart live cage trap
The department also has the power to issue burn permits to destroy harborage
sites such as brush piles.
Sale of ground squirrel control materials:
CDFA maintains a registered label for grain bait specially formulated and dyed
for the control of ground squirrels. This material can only be purchased through
the County Agricultural Commissioner Offices. These control materials are only
for sale to individuals who are experiencing damage due to ground squirrels and
cannot be sold for profit.
All requests for the purchase of control materials shall be screened by our
biologists to determine if the material that the person wants to purchase and the
method and setting are appropriate for controlling ground squirrels. Individuals
who request to purchase materials must be licensed as a qualified applicator.
Private individuals must first take and pass a written examination developed and
administered by our department before we will sell them control material.
Generally, we only sell treated bait for bait station use to private individuals
because we have found that they have a greater tendency to improperly
broadcast bait either by piling the bait or putting it out at a much higher bait per
square foot density than is recommended. Bait misapplied in this way leads to a
chance of non target take.
Prior to all sales special consideration is made to determine if the proposed
application site is within threatened or endangered species habitat.
The following materials are available for purchase at our cost:
Diphacinone or Chlorophacinone .01% (anticoagulant, grain bait for
Diphacinone or Chlorophacinone .005% (anticoagulant, grain bait for
Pre made bait stations
Exotic Pests: The need to protect our food supply and environment from
invasive species is greater than ever. With the increasing movement of people
and commerce, our environment and food supply is at serious risk from the
accidental or intentional introduction of exotic and invasive species. Invasive
species are considered the second greatest threat to biological diversity (after
habitat loss), and range from plants and animals to insect pests and various
diseases. Ecologists increasingly refer to this collection of invasive organisms as
“biological pollution”, a significant threat to California’s human health, commerce,
and environment. California is particularly vulnerable because of because of the
diversity of its agricultural production and the trade of agricultural products with
other states and foreign countries. Further, California:
• Serves as a major gateway into the United States for international
trade via land, sea and air.
• Has the largest single land international border at San Ysidro, and the
sixth busiest port in the world in Los Angeles;
• Is home to over 10% of the nation’s population;
• Produces $38 billion annually in agricultural production, and is 15% of
the nation’s agricultural production value; and
• Supplies over 40% of the nation’s fruits, nuts and vegetables.
Since 1993, the value of U.S. imports has doubled to approximately $42 billion.
The reduction in international trade barriers has increased California’s exports by
68%. From 1980 to 2000 there was a 127% increase in international passenger
arrivals. Volumes of air cargo are doubling every 5 to 6 years and an increasing
percentage of this cargo consists of perishable commodities such as cut flowers,
fruits and vegetables that could potentially serve as a mode of transport for
invasive species or disease.
The Department’s pest management programs are an integral part of a statewide
web designed to 1) exclude; 2) detect; 3) eradicate; and 4) manage exotic pests.
The major focus of the program is placed on exclusion and early detection
activities. This is reflected by the 33,174 hours of staff time that was dedicated to
these activities by our Department in FY 05/06.
A study at The University of California, Berkeley found that investment in pest
prevention has returned 8 to 14 times the cost in economic benefits, when just
four of the numerous exotic pests that are targeted have been kept out of the
State. This estimate does not include the external costs of impacts on the
environment and public health from the increased pesticide use that is averted.
The desire for the State and County program is to keep the eradication and pest
management activities as a secondary response. This is reflected by the 4,972
hours of staff time expended on these two activities in FY 05/06. Nevertheless, it
is critical that the Department be able to respond quickly and effectively to exotic
pest introductions, using methods and procedures that have been approved and
recommended in consultation with USDA, CDFA and the University.
Early detection through adequate surveillance for biological pollution is critical for
an effective response. When a new pest or disease is delimited quickly, multiple
eradication options may still be available. But, the response to the pest/disease
find must also be timely and effective. As an example, if foot and mouth disease,
one of the most highly contagious animal diseases know to man, were introduced
into commercial livestock, the exponential spread would be catastrophic. A study
published by the Agricultural Issues Center in 1999 estimates that the total direct
and indirect losses in California alone would reach $13.5 billion. Because this
disease spreads so rapidly, the cost of control and eradication increases
$1 million to $2 million every hour a response is delayed or the disease goes
Similarly, actions taken during the first hours of an outbreak will have the greatest
impact on eradication success. Government inquiries into the foot and mouth
disease outbreak in the United Kingdom in 2001 have concluded that, although
agricultural movement restrictions were placed on livestock within three days
after the first reported case, this was considerably too late and contributed
immensely to the difficulty in containing and eradicating the disease.
A specific example for Contra Costa County would be our response to the
Glassy-winged Sharpshooter (GWSS) infestation in Brentwood. After following
delimitation protocols we determined that the infestation was limited to one
specific development comprising of approximately 200 homes in Brentwood. The
Board of Supervisors took emergency action and authorized the Department of
Agriculture to initiate an eradication program using materials recommended by
CDFA. Every home was given notice in English, Spanish and Tagalog of two
public meetings. In addition, staff contacted and received verbal consent from
each home owner to treat their yard landscaping with the exception of one home
owner. This action resulted in all but one home being treated. The outcome:
• It was only necessary to spray the residential properties once while all
other eradication programs for GWSS that have been conducted in
Northern California have required multiple residential sprays over a
period of more than one year.
• Contra Costa County was the first county to successfully eradicate a
GWSS infestation and be removed from quarantine.
• Inconvenience for local home owners was kept to a minimum.
• Contra Costa County growers were allowed to continue shipping their
grapes to counties such as Napa, Sonoma and Mendocino.
Noxious Weeds: Although few economic assessments have been conducted for
“A” rated weeds that are established in California millions of dollars are spent in
detection and eradication efforts every year. This is done to limit their known
potential negative effects on, livestock grazing and forage harvesting, yield and
forage quality of rangelands and other terrestrial and aquatic habitats. “A” rated
weeds by definition are extremely invasive and difficult to control. In California,
livestock and wildlife grazing capacity can be reduced up to 90 percent
depending on the species. Because of the taste, texture and toxic qualities of
many weeds, livestock and wildlife avoid grazing in heavily infested areas. Thus,
noxious weeds can greatly increase the cost of managing livestock.
In addition to decreased productivity of rangeland, pastures and grasslands,
invasive weeds can, if they become established, create road hazards such as the
obstruction of vision and the blowing of weeds across freeways. Some species
of noxious weeds can directly effect and invade grain fields, orchards, vineyards,
cultivated crops, and wastelands. These invaders can also reduce access to
recreational areas. In addition, noxious weed infestations can reduce wildlife
habitat and forage, displace native plants, and decrease native plant and animal
diversity. Sites high in herbaceous foliar cover and soil fertility, and hot spots of
plant diversity (and biodiversity) are invasible. Exotic plant invasions in rare
habitats and distinctive plant communities pose a significant challenge to land
managers and conservation biologists. Dense infestations not only displace
native plants and animals, but also threaten natural ecosystems and nature
reserves by fragmenting sensitive plant and animal habitat.
Recent studies indicate that many weed species significantly deplete soil
moisture reserves in annual grasslands and other natural habitats in California.
“A” rated aquatic weeds including hydrilla and Alligator Weed can severely affect
agriculture by impeding the flow and availability of water. They can have
devastating biological effects by creating aphotic zones in the water column.
Often when they die from cold winter temperatures they create anoxic conditions
in the water and can carpet the benthos with a suffocating layer of decomposing
vegetation. This can also occur if the weeds are treated with herbicide after they
have attained significant growth.
If no action is taken to prevent the introduction and spread of noxious invasive
species they would enter, thrive and spread throughout susceptible habitats in
Contra Costa County. With no control noxious weeds could spread over
hundreds of thousands of acres. Population densities would increase to over
85% in rangelands depending on soil, slope, existing woody vegetation and
exposure. This would decrease the value of the land for forage proportionately,
making cattle grazing economically untenable. Recreational lands would in many
cases become untenable as weeds can severely affect access and usability.
County land owners would find it difficult to control these known noxious weeds
on their property especially if it was near uncontrolled populations. The value of
property for agriculture could drop significantly. Wildlife habitat and species
diversity would be severely affected as large areas would be covered with
noxious weeds. There would be devastating effects on endangered species
such as the Contra Costa gold fields, large flowered fiddleneck and soft bird’s
Aquatic areas would become clogged with weeds making navigation impossible.
Boat owners and marina operators would demand action, perhaps after the
problem has grown to massive proportions. Winter die off of the weeds would
create anoxic conditions in many bodies of water in the county and state severely
effecting fish birds and mammals. Endangered species such as the Sacramento
split tail, Winter-run Chinook salmon and Red legged frog would suffer.
Recent studies of weeds in Nevada show that new infestations of noxious weeds
often grow at a rate faster than 60% per year and one plant can create an
infestation of up to 36,000 acres in as little as ten years if left uncontrolled.
Methods of application include wick applicator, paint brush, backpack sprayer,
handheld sprayer, power tank sprayer or by air. Herbicide costs range from $10-
$50/acre and application costs range from approximately $15-$90/acre for
applications made by air or ground spray rigs. In most cases control has to
continue for many years in order to deplete existing seed banks.
The potential harm from “Q” and “B” rated weeds is very similar to that discussed
Ground Squirrels: Ground squirrels damage many food-bearing and ornamental
plants, such as, nut and fruit trees and vulnerable grains. Ground squirrels will
enter gardens and devour vegetables and undermine structures. They will gnaw
on plastic sprinkler heads and irrigation lines. The loss of forage to squirrels
goes beyond the weight of green matter they consume. The most important
competition occurs when squirrels feed on the tender young sprouts of annuals,
whose growth may be retarded or stopped altogether by close grazing. Squirrels
also eliminate vegetation by clearing and trampling areas around burrows and
Ground squirrels significantly reduce the amount of green forage available to
grazing cattle. In one experiment (Howard, et al, 1959), the reductions in daily
weight gain by cattle due to California squirrel activity were 1.03 and .75 lbs. for
the 93 and 62 day winter growth periods in successive years. Based on the
amount of green forage (4 oz) consumed daily by ground squirrels, Grinnel and
Dixon (1919) estimated that 20 squirrels eat as much as one sheep, and 200
squirrels eat as much as one steer. The loss of forage to ground squirrels can be
felt most by the producer during drought years. This of course is difficult to
predict and plan for. Currently, in Contra Costa County, the average rangeland
lease on a per acre basis is $18.33. Ranches that are heavily infested with
ground squirrels would be forced to have fewer cattle, lease more ground to
support their existing herds or supplemental feed with hay. According to the
2002 crop report for Contra Costa County, the price of hay averaged $105 per
Ground squirrels can burrow beneath buildings, railroad tracks, bridges, canal
and levee systems, highways and schoolyards. The threat of seepage or
collapse of levees and ditch-banks requires the elimination or control of these
burrowing rodents where they inhabit such structures. Permanent exclusion of
squirrels is delayed by devices such as concrete linings at a cost but is only
temporary. The edges of such lining are undermined and any small crevice within
the system will be quickly turned into a collapsed lining.
Cost for repairs due to ground squirrel burrows is expensive. Contra Costa
County Water District estimated that it cost $36,271 to repair a small section of
canal system liner that was damaged by ground squirrel burrows. The
neighboring homes were being threatened due to the erosion that occurred from
the same ground squirrel burrows and as a result lawsuits were being developed
against the Water District.
Other areas where ground squirrel burrowing is unacceptable include golf
courses, railroad rights-of-way, horse pastures and cemeteries. A local cemetery
had to endure the difficult job of repairing caskets damaged by the burrowing of
ground squirrels. The squirrels had undermined some burial plots and began to
unearth pieces of caskets and human remains. Not only was there a cost
involved for the cemetery but also the emotional trauma those family members
had to experience when this was discovered.
In 1991 Concord High School was threatened with lawsuits involving families of
students who had been injured from stepping into ground squirrel holes on the
baseball field. Not only were the squirrels causing damage to the fields but were
also entering classrooms and being handled by students. The liability of the
school district was tremendous and they hired a professional pest control
operator to control the problem. The high school problem originated from the
nearby Naval Weapons Station who was also experiencing a severe ground
squirrel infestation. The ground squirrels were burrowing in the earthen
magazines that housed ammunitions and threatened to compromise the safety
features for which they were designed. The cost to the Naval Weapons Base in
1991 was approximately $15,000.
Ground Squirrels can harbor diseases harmful to humans, particularly when
squirrel populations are dense. A major concern is bubonic plague transmitted to
humans by fleas carried on the squirrels. Ground squirrels are susceptible to
plague, which has wiped out entire colonies. Individuals are not to handle dead
squirrels under these circumstances. Ground squirrels are also associated with
the spread of Rocky Mountain spotted fever, rat bite fever, tularemia, Chagas’
disease, adiospiromycosis and encephalomycarditis.
Ground squirrels are known to eat eggs of ground-nesting birds, such as
pheasant and quail. In a study on the nesting of California Valley Quail made on
the San Joaquin Experimental Range in 1937 by the State Department of Fish
and Game, it was concluded that 30 percent of the unsuccessful quail nests
resulted from ground squirrel predation.
Our Deputy Agricultural Commissioners and Chief Deputy Agricultural
Commissioner provide immediate oversight of our various programs. CDFA and
the Department of Pesticide Regulation also assess our programs to insure that
we are meeting regulatory requirements for pesticide use and contract
Daily and monthly records are generated and maintained on all pesticide use in
our programs. This use is reported to the California Department of Pesticide
Regulation. A report of all use is reported to CDFA. All sales of ground squirrel
baits and gas cartridges are reported to CDFA. Program activities involving Pest
Exclusion, Pest Detection and Pest Management are recorded and reported to
CDFA on a monthly basis.
The department is in touch with the latest technology through the various training
seminars that staff attends. We have frequent contact with CDFA and UC IPM
experts and maintain contact with other agencies within the county through the
Alameda/Contra Costa Weed Management Area and through other organizations
both inside and outside of the county. The department is always striving to
improve our programs.
A 50¢ per pound surcharge is collected on all sales of ground squirrel baits and
gas cartridges. This surcharge money is sent to CDFA and is used solely on
research in an attempt to find new, safer and more effective vertebrate pest
Agriculture Addendum 1
History of Ground Squirrel Control in Contra Costa County
Controlling the damage caused by ground squirrels has been an issue impacting
government in Contra Costa County for over 120 years. During that time the
County has tried various approaches with their program ranging from abatement,
free rodenticide, free labor, consultation, or no program at all.
As early as 1874 an abatement law “An Act to Abate the Squirrel Nuisance in
Certain Counties of the State of California” was passed by the State Legislature
making the ground squirrel a public nuisance and subject to eradication in the
counties of Alameda and Contra Costa.
The records of the U.S. Public Health Service show that in 1900 the Bubonic
Plague was discovered in San Francisco. In 1903 Contra Costa County had 3
cases reported and by 1927, 15 cases-13 resulting in death. During this period,
ground squirrels in Contra Costa County were confirmed, for the first time, to be
carriers of the plague.
In 1909 a general campaign of eradication was conducted. Free grain bait, as
well as carbon bisulfide, was distributed to residents of the county to combat the
squirrel and plague menace.
In 1916 the County Board of Supervisors appointed a Horticultural Commissioner
with a main function of controlling ground squirrels. The present title of
Agricultural Commissioner was changed in 1930.
By the 1940’s the Agricultural Commissioner’s office consisted of 9 squirrel
inspectors, each in charge of a district. This responsibility consisted of enlisting
cooperation of each landowner, supervising the application of the poisons and
collecting fees for the materials sold.
In the 1950’s, 60’s, and 70’s the County Board of Supervisors returned to a more
aggressive approach and supported a ground squirrel eradication program. All
services and materials were free of charge. There were 5 full time and 2 part-
time squirrel control employees when the program ended in 1981. The program
ultimately ended due to budget cuts resulting from State Proposition 13.
In 1990, the County Board of Supervisors approved filling one Biologist position
in the Department of Agriculture. This was due to pressure from the agriculture
industry of the growing ground squirrel problem. The positions responsibilities
consist of completing contract work for ground squirrel control based upon
agreements established with persons/agencies. The Biologist also provides
expertise and helps growers coordinate efforts to control ground squirrels. This
is the current program of today.
Issues Affecting Control Efforts
After 120 years of efforts to control and eradicate ground squirrels, the current
residents of Contra Costa County have never seen the population densities and
damage which can be attained when the squirrels are allowed to reach natural
population levels. The effects of these squirrels were so impressive that early
explorers as far back as Sir Francis Drake, in 1579, made not of them in their
The County Department of Agriculture is aware that with our current level of
control, ground squirrel populations are growing and are moving back into areas
where they had previously been eradicated. County government will continue to
receive demands to control the problem, just as demands were made over 120
years ago. However, there are a number of issues which make ground squirrel
control more complicated today:
Public Perception-public acceptance of control programs is harder to obtain
since more of our citizens live in urban rather than rural areas. However,
growing development as generated a new awareness of ground squirrel damage
due to new housing subdivisions within ground squirrel habitat or adjacent open
space. There is an increase of homeowner requests to purchase control
materials for ground squirrels in backyard settings that are adjacent to open
Conflicting Goals-the Endangered Species Act has created situations where
there are conflicting goals. Special interest groups may object to the use of
materials that control ground squirrels.
Loss of Control Materials and Cost Effective Alternatives-few products are
still registered for vertebrate pest control in open space and rangeland areas.
Many of the products used long ago are no longer available. Losing vertebrate
pest control materials is a major concern. Materials that are still available are
more time consuming to use due to the nature of the toxicant.
Funding-the department’s current directive is to charge for services when doing
ground squirrel control work. Since this service was provided to growers free of
charge in the 50’s, 60’s and 70’s, many growers complain that the County is not
providing services in support of agriculture. Most of the current funding has
come from other agencies who are trying to protect infrastructures. The growing
ground squirrel population has forced some growers to pay for services when the
alternative is a major crop loss.
The ability for the agricultural community to fund ground squirrel control can vary
from year to year. Prices of certain agricultural commodities may drop
substantially where as forcing growers to pay for ground squirrel control can
damage the ability of agriculture to survive rather than help preserve it. At the
same time, the grower who is spending money each year to control the pest has
a legitimate complaint when nothing is being done next door.