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OAK WILT: CAUSE, PREVENTION AND TREATMENTS
                                   by Priscilla Stanley


On November 12, 2001 Robert Edmonson of the Texas Forest Service, Johnson City
office, made a one hour presentation to the Tierra Linda Garden Club. Robert has a
degree in Forestry from Texas Tech and has been helping residents in Tierra Linda
since 1993. Robert can be contacted in his office at 1-830-868-7949.

The following is essentially a transcript of Robert Edmonson’s presentation, including
the questions asked by our homeowners. (11/04 This article has been reviewed and is
still current in content.)

                                       OAK WILT

Oak wilt is caused by a fungus. Oak wilt affects both urban and rural areas.

How do you recognize and diagnose oak wilt?

Live Oaks: In live oaks, the symptoms are veinal necrosis (dead veins) which has a
yellow fish-skeletal appearance on the elliptical green leaf, or the reverse, with a green
fish skeletal appearance on a yellow leaf. These leaves fall from the tree. There can
also be oak wilt cases where the end of the leaf dies or where the margin of the leaf
dies. These latter symptoms could also be due to other causes, such as salt damage,
herbicide damage, or freeze damage. Veinal necrosis on live oak leaves is however
very diagnostic of oak wilt. A healthy tree can suddenly begin dropping leaves, and
dropping more leaves, until the leaf canopy becomes very thin. Eventually the entire
canopy is gone. This process can take as little as 3 to 6 months from initial infection to
death.

Red oaks: With the red oaks, including Spanish oaks or blackjack oaks, you really
do not have a good leaf characteristic to diagnose oak wilt. The literature describes
“watersoaking” or “bronzing” of red oak leaves caused by oak wilt, but these
characteristics are difficult to identify. The main diagnostic criterion for the Spanish
oak is the leaves turning red at the wrong time of the year. This color change
occurs very rapidly; all of a sudden the entire tree turns red. A red oak dying of oak wilt
holds onto its leaves (it does not drop them like the live oak). This process, from initial
infection to death, can happen as quickly as 4 to 6 weeks, or even as quickly as a week
in a red oak.

Oak wilt can also be diagnosed by sending a fairly large sapwood sample to a lab
where they culture for the fungus in a petri dish. Taking the large sapwood sample is
damaging to the tree, and thus this is not a good method to diagnose oak wilt.
OAK WILT Presentation on November 12, 2001                                               Page 2
Robert Edmonson of the Texas Forest Service



Oak wilt is best diagnosed by observing the visual symptoms on the leaves and
the pattern of death of the tree.

How does oak wilt spread?

Oak wilt spreads by two routes:
1. Transmission via the interconnected root system from a nearby infected oak
tree.
Live oak mots (groves of live oaks) all share a common root system, since many of the
trees arise from root sprouts on existing trees. Thus, if one tree gets oak wilt, it travels
through the common root system to other trees at the rate of about 75 feet/year.

Oak tree roots extend out about three times the height of the tree (note: this is
much further than the dripline of the tree.) Thus, a 20 foot tall tree can have roots
extending 60 feet out from the trunk. When trees are blown over in a storm, the root
system seems small because most of the roots broke off and remain in the soil.

If a live oak root touches the root of another live oak, the roots will readily graft with
each other. Red oak roots are less likely to graft together.

Oak wilt spreads readily via these grafted and common root systems at an
average rate 75 feet/year. Oak wilt centers have been documented where the disease
hardly moves or moves very slowly. Conversely, oak wilt has been documented moving
at up to 150 feet/year. There are many variables, such as weather conditions.

2. Beetles carry fungal spores to cuts or wounds on the oak tree
If one tree in a large group of healthy trees gets oak wilt, it was probably caused by
insect transmission, or use of tools, such as pruners or pruning saws,
contaminated with spores from a tree infected with oak wilt.

If a red oak (such as a Spanish or blackjack oak) contracts oak wilt, and the conditions
are favorable (the necessary moisture and temperature), the fungus can form fungal
mats on the wood of the red oak. The oak wilt fungus can be likened a mushroom, and
the spores formed by the fungal mat can be likened to seeds. The fungal mat forms
between the bark and the wood. The fungal mat is loaded with spores and has a strong
odor of fermenting fruit, which is attractive to tiny sap beetles (only 2 - 3 mm in length).
You are unlikely to see either a fungal mat, which is mostly under the bark with only a
crack in the bark above it, or a sap beetle. You can smell fungal mats in the woods,
especially in the Spring. The sap beetles feed on the fungal mats and get spores
stuck to their bodies. The sap beetles then fly around looking for fresh wounds
on trees for more sap to eat. If a beetle carrying a spore feeds on a fresh wound
on an oak, the spore can germinate and the fungus colonizes the tree. If the tree
is a live oak, having interconnected roots, the fungus will reach all of the trees
eventually. If it is a red oak, the entire fungal mat cycle begins again. This is clearly
undesirable.
OAK WILT Presentation on November 12, 2001                                             Page 3
Robert Edmonson of the Texas Forest Service



Fungal mats are generally formed in the Spring of the year (February, March and April).
Sap beetles can be active during the Spring, depending on the temperature. Do not
wound or prune your trees during the Spring (February through June in Hill
Country). Spring is the most dangerous time of the year for oak wilt, the time
when you are most likely to start a new infection. By the Summer, the fungal mats
are dried up and gone, BUT the little sap beetles may still be carrying spores around so
you still need to paint wounds immediately. Winter, when it is really cold, is a good time
to do major pruning on oaks since the beetles are not likely to be flying around.
Pruning should be done in the windows when you don’t have all three of the
ingredients necessary to contract oak wilt:
        1. fungal mats of spores
        2. sap beetles flying around
        3. fresh wood

Oak trees grow very well without any pruning. Pruning is not necessary for the
health of oak trees.

Why don’t we just spray all of the sap beetles?
How long have we been fighting mosquitoes, house flies, cockroaches, fire ants,
grasshoppers etc.. You are not going to control the sap beetles any better.

Prevention of oak wilt:
1. Immediately paint all wounds and cuts on all oaks in all seasons,
whether the branch removed is dead or alive.
Any time you prune an oak, any oak, including live oaks, Spanish oaks, blackjack
oaks, Monterey oaks, Bigelow oaks, shin oaks, bur oaks, post oaks, lacey oaks,
chinquapin oaks etc., paint the wound. If the tree is not an oak, if it is a cedar elm,
sycamore, ashe juniper, a cherry, do not paint the wound. Non-oaks do not get oak
wilt. Only oaks get oak wilt. The purpose of the paint is not to seal the wound. You
are just putting some “goop” on the wound to make it unattractive to the sap beetle.
You must paint the wound immediately - cut and paint, cut and paint. You can use
any type of paint, such as cheap spray paint, water-based latex in a spray can, etc. It
does not have to be the expensive black pruning paint. (Note: Auto undercoat spray
paint at Walmart is cheap and work well.) You just need paint on the wound for 3 days.
After about 3 to 4 days, the tree will start to heal and there is no longer sap coming to
the surface. There is then nothing attractive to the sap beetle and your tree is safe. If
you prune, and then come back 3 or 4 days later to paint, it is too late. The branches
that you have pruned off do not need to be painted since they are no longer attached to
the tree, and thus the sap and the beetle are not a threat to the tree.

2. If you have a red oak (Spanish or blackjack) oak that you suspect died of oak wilt
(e.g. a Spanish oak turns red and dies suddenly in June), you should destroy the tree
by cutting it down and burning it, or burying it, or girdle the tree as low on the trunk as
possible to dry the tree out as rapidly as possible. Each of these steps is intended to
OAK WILT Presentation on November 12, 2001                                          Page 4
Robert Edmonson of the Texas Forest Service

prevent the red oak from forming fungal mats. It is good to destroy diseased red oaks
in this manner, but there is so much innoculant around Tierra Linda, that this might be
only a minor contribution to preventing the spread of oak wilt.

The only thing you can really control is your pruning - if you prune,
when you prune, and whether you paint the wounds immediately.
Sap beetles live perhaps one year and are attracted to sap from all trees. The oak wilt
spore will not germinate if it lands on a cedar elm or a cedar tree. The spore will
germinate only on an oak.

What about wounds on oaks caused by wind damage, livestock or wildlife?
The Forest Service has flown over almost every quad map in Central Texas looking for
oak wilt centers. These coordinates are being plotted by computer. There is a direct
correlation between the incidence of oak wilt and human activity. You find oak
wilt around houses and on highways, utility corridors, fencelines etc.. When you
get out in the middle of nowhere, you do not find oak wilt. People cause oak wilt.
We get the brand new chain saw - we’ve got to use it. People think, “It’s Springtime.
I’ve got to prune the trees.” People are out there constantly messing with the trees,
cedar clearing, especially with bulldozers smacking trees up all over the place, and new
oak wilt centers are started up. We get a developer who buys a huge piece of property,
they start cutting in roads and pushing and piling, and new oak wilt centers are started
up. They cut a new road through an area and cut trees without painting the oaks and
oak wilt starts up.

Q: What does the Forest Service do to get the County and Central Texas Electric
to paint wounds on oaks?
A: The Forest Service does the best it can. The Forest Service gives pruning
presentations and oak wilt talks to different local, county and state government
agencies, to different companies and electric and telephone utilities. The information is
out there.

Q: What is their attitude?
A: They are very receptive to a lot of it. That’s fine and dandy when I am talking to the
supervisor, but by the time the word filters down to the guy out in the field running the
chain saw... All we can do is provide them with the information. Whether they choose
to use it or not depends on their company policy, and how they reprimand their
employees who are not obeying a specific policy is all in-house on their part. The
Forest Service has no authority to compel compliance.

Q: Can oak wilt-contaminated tools spread oak wilt? How can they be sanitized?
A: The likelihood of transmitting oak wilt from tree to tree with pruning equipment is
low. Oak wilt is caused by a little organism, a fungus, and it’s a very fragile fungus. It
you heat it above 95F, or you drop the moisture below 20% in the tree, you kill the
fungus. The fungus cannot tolerate those conditions. A chain saw blade gets hotter
than 95F and so it kills the fungus. For a pole saw, or a hand saw, you should sterilize
OAK WILT Presentation on November 12, 2001                                           Page 5
Robert Edmonson of the Texas Forest Service

your equipment between trees because of other tree diseases that could possibly be
moved through the equipment. One example is fire blight that affects any plants in the
rose family, such as pyracantha, peaches, pears, cherries, etc.

It is a good idea to sanitize your saws and loppers with rubbing alcohol, Lysol
spray disinfectant, or a 10 - 20% bleach solution (such as Clorox) for 30 seconds,.

Q: What about firewood? Is it safe to burn wood from a tree that died of oak
wilt?
A: Yes, it is perfectly safe. You cannot spread oak wilt in smoke. What happens
to most living organisms if you set them on fire? They die.

The problem is moving around infected firewood. If the wood is dry, seasoned, the
bark peels off of it easily, something you would want to put in your fireplace anyway,
because it’s dry and isn’t going to just sit there and smoke and smolder, it is fine; it is
safe. Whether it died from oak wilt or not, as long as it is dry, it is safe. When you
drop the moisture in the wood below 20%, the fungus dies.

If the wood is still green, and you cut it from an oak wilt-affected tree, leave the
wood on site until it seasons and dries. Then you can safely move it. It must be
dry. Generally here in Hill Country, hot as it gets in the summer, if you cut the wood in
the Spring, you can burn it that Winter. If you cut wood in November, let it sit because it
will not dry out enough for use this Winter.

How do you deal with oak wilt?
There are four ways:

1. Prevention, discussed above.

2. Trenching The disease moves through interconnected roots. Thus, if you can
disconnect those roots, you can isolate a disease center. You can stop it from
spreading. Think of a fire burning, and you put a fire line around the fire. The fire burns
up to the line and stops. This is what happens with trenching. Since 1988, the Texas
Forest Service has assisted landowners with the installation of over 2.5 million feet of
trench lines statewide. This is equivalent to a trench from Houston to Lubbock. We
have contained somewhere in the neighborhood of 1,600 oak wilt centers
statewide. The success rate is about 2 out of every 3 trenches, which is about 65
- 70% success.

You folks who have been in Tierra Linda since 1992-93 are familiar with the trenching
that was done here. We have not been very successful with the trenching done at
Tierra Linda. The reason is that there are two rules of trenching that must be met
or the trench is not going to work.
OAK WILT Presentation on November 12, 2001                                            Page 6
Robert Edmonson of the Texas Forest Service

1. Placement of the trench: Place the trench at least 100 feet from the last known
symptomatic tree. There is a buffer zone of healthy trees between the diseased trees
and the trench. This is very, very important.

2. Sever all of the roots. This is where we got into trouble in Tierra Linda. The trench
must be dug to a depth sufficient to get all of the roots cut. In the past, most of the
equipment used out here was a bulldozer pulling a ripper bar behind it. Some of you
probably saw the machine and the big mess that it made. That was the best thing that
we had at the time. The problem is the rocky soil out here. There is so much rock,
ledges, shelves, and fractured rock, so there are roots that were impossible to reach
and sever using a bulldozer with a ripper bar. The ripper bar could hit a rock and them
ride up over some roots, leaving some root connections that spread the oak wilt. That
was in the past.

Now there is new equipment available. There are now rock saws that have the
capability of cutting 54 to 60 inches deep. This is a giant machine that does
excellent work and can cut through just about anything. These new rock saws
have been in use for the past two or three years, so it is a little early to know the
effectiveness of these rock saws versus the early saws that did not cut as deep. In 6 or
7 years, sufficient data will be available to evaluate the effectiveness of these large rock
saws. Preliminary indications are that the effectiveness of trenching will increase from
65 - 70% to 75 - 80%. Trenching with a 54 or 60 inch rock saw costs $3.25 to
3.50/linear foot. The trench can be covered immediately after it is installed (it does not
need to stay open).

The Forest Service does not recommend using the smaller 36 inch rock saws you can
rent because they can only cut 28 inches deep, which does not sever all of the roots.
Bulldozers pulling a ripping bar are not an option for Tierra Linda because they do
not sever all of the roots in our rocky soil, which results in a high frequency of trench
failure.

The large belt trenchers used for highway work to install large sewer lines work well, but
they cost $3,000/day.

Backhoes can be very effective where there is deep soil and not a lot of rock. There
are many backhoes available so the cost is only $1.50/linear foot. A backhoe can
trench up to 4 feet deep, so it can achieve the depth required for effective oak wilt
control. The trench is wide enough that you can climb down into the trench and inspect
for roots. You just keep digging deeper until you don’t see any more roots.

Q: How wide does the trench have to be?
A: Width does not matter. Depth is critical to success.

Q: Do the roots grow back across the trench?
OAK WILT Presentation on November 12, 2001                                            Page 7
Robert Edmonson of the Texas Forest Service

A: Yes, eventually. Oak wilt moves through oak roots at about 75 feet /year. The
trench is placed 100 feet in front of the advancing oak wilt, which is 1.5 to 2 years
ahead of the disease.

The Forest Service has dug up old trenches to see what happens over time. Rather
than growing roots across the trench, the roots tend to run up and down the
trench in the loosened soil of the trench. The trees that will die, will die long before
roots cross the trench or any root grafting (which is a slow process) occurs. There are
trenches that are 12 - 13 years old that are still holding, preventing the oak wilt from
crossing the trench. Timing is important. You want the disease to challenge the
trench relatively soon. If you trench around an oak wilt center, and 3 years later the
disease is up to the trench line all the way around, then it is likely that the trench will
contain the oak wilt. Where you get in trouble is if you misplace the trench. If
inspection after one year shows that the disease is already to the trench line, then it
means that the trench was not put in the right place, and the trench might fail to contain
the disease. Alternatively, if the disease just sits there and doesn’t move, there is a
higher likelihood that the disease will break out of the trenched area.

You can improve the effectiveness of your trench by a few percentage points if you
install the trench and then push over all of the oaks inside the trench. This is very
difficult for most people to do because they see the buffer zone of live trees. Those
trees are alive today, but actually they are dead - they just don’t know it yet. The Forest
Service highly recommends pushing over all the trees inside the fence and burning
them, but this doesn’t happen very often.

Ultimately, three years after trenching, you hope to see dead trees right up to the trench
line, and live oak trees just outside the trench line.

3. Alamo fungicide treatment: Let’s look at the trees in the Tierra Linda picnic area
as an example. You have oak wilt all around the picnic area. There is no way to install
a trench because you do not have the 100 foot buffer, and you have infrastructure (the
pool, paved road etc.) in the way. The only option to try to save the trees is to have
them treated with the Alamo fungicide. Think of it like an inoculation. You put fungicide
inside the tree. The fungus comes and tries to get in the tree, but it can’t. Eventually
the fungus moves on and the tree is left alive. In an ideal world, that is how it works.
The treatment works more times than it doesn’t, but it is by no means a cure or a
guarantee.

Neither trenching nor treatment with Alamo is a guarantee that you will be successful.
There is no cure for oak wilt.

Treatment requires drilling injection holes 4 to 6 inches apart along the flare roots of the
tree (down one side of the flare root and back up the other side of each flare root), all of
the way around the tree. Alamo is mixed with water at a concentration based on the
diameter inches of the tree measured at 4.5 ft above the ground and injected into the
holes via a harness of tubing and T-shaped injectors connected to a pressurized tank.
OAK WILT Presentation on November 12, 2001                                           Page 8
Robert Edmonson of the Texas Forest Service



Q: How long does Alamo treatment protect an oak tree?
A: Alamo treatment lasts a couple of years. If you treat the trees at the proper time,
when the trees are within 100 ft of known disease, which is just before the disease
reaches the trees, then the disease comes along, and the tree remains alive. If the
disease is still active in the immediate area after two years, then you would re-treat the
trees.

Trees should only need to be treated twice, because after a four year period, the
disease should have moved through and out of the area. This is the same principle as
a fire burning toward your house. You hose your house down, and the fire burns past
your house because you have protected it, and then the fire is gone. There is no need
to keep hosing your house down once the fire has moved past it. This principle also
applies to Alamo treatment once oak wilt has moved out of the immediate area.

Treatment of the trees on your property is a judgment call. If you treat every tree on
your property, then it is difficult to judge the progression of the disease. Robert
Edmonson prefers treating just the significant trees, leaving the others as indicators to
monitor the progression of the disease through the property in order to determine
whether or not you need to treat again two years later.

Some contractors will send you a flyer every two years telling you that it is time to
retreat your trees. It is not automatically necessary to re-treat your trees every two
years. It depends on the rate of progression of the disease on your property.

Q: Is there such a thing as “oak decline”?
A: Oak wilt is caused by the fungus Ceratocystis fagacearum. Oak decline is a stress-
induced problem. There are several diseases that cause decline. For example, you
have oak trees and you build a parking lot around them. Over the course of the next 20
to 25 years, the trees slowly begin to die. The trees across the street in an open lot are
healthy; the decline disease never affects those trees. The paving of the parking lot
and the soil compaction were the initial stress factors. Over the course of time, these
factors are slowly killing the trees. Eventually, it reaches the point where even removal
of the parking lot cannot save the trees because they are too far gone. This is the
textbook definition of “oak decline”.

Here in Central Texas, folks use the terms “oak wilt”, “oak decline” and “oak blight”
essentially interchangeably.

Drought is also a stress causing oak decline.



Q: How much does Alamo cost?
A: Generally, the current price is about $250/quart. In the old days, Alamo was used at
the rate of 2 to 3 mL/diameter inch of tree. Now Alamo is used at the rate of 10 to 20
OAK WILT Presentation on November 12, 2001                                            Page 9
Robert Edmonson of the Texas Forest Service

mL/ diameter inch. One quart of Alamo treats a tree (or trees totaling) about 50
diameter inches. If a contractor treats your trees, it will cost about $15/diameter inch, or
$150 to treat a 10 inch diameter tree. (Note: Oak Wilt Specialists of Texas in
Wimberly, TX has treated trees in Tierra Linda for $11/ diameter inch.)

Robert Edmonson recommends using the maximum allowable Alamo treatment
rate of 20 mL/diameter inch. If you are going to the trouble and expense of treatment,
you want the best likelihood of success.

The old Alamo was gold colored. The active ingredient in Alamo is propiconazole,
which does not dissolve in water. The old gold Alamo used a petroleum-based carrier,
including benzene, xylene etc.. The current Alamo formulation contains micro-
encapsulated propiconazole which can be suspended in water. This new technology is
a bit more expensive, but it is safer water-based formulation, which permits the higher,
more effective dosage rates in the trees. If you are going to inject a fungicide into
an oak tree, it should say “Alamo” on the bottle and it should be a blue liquid.
The Texas Forest Service does not recommend using any other product.

Q: Isn’t there a cheaper chemical that can be used?
A: No. Alamo-brand fungicide is the only product that is legal in this application
and is labeled, researched, tested, and that you are allowed to use. Period. Yes,
there are other products on the market that contain propiconazole, but they contain
other chemicals as well, and they are not labeled for the treatment of oak wilt. If you
use a fungicide in a manner inconsistent with its labeling, you are violating a Federal
law. The other products contain other chemicals, other carriers, other fungicide
components; we have no idea what they will do to an oak tree since no testing has
been done in oak trees, since these products are not allowed to be used on oak trees.
Alamo is 14.3% propiconazole and 85.7% water. There are no other chemicals in
Alamo, other than the blue dye. Robert Edmonson will not personally use any chemical
other than Alamo to treat oak wilt.

Alleged Alternative Treatments: Other companies and other products claim to be
able to stop oak wilt. The Texas Forest Service has asked for data from these
companies to support their claims, and has asked them to participate in field tests to
support their claims. The Forest Service has checked on the background of some of
the founding members of some of these companies and found that they were lying
about their credentials. The person was not a professor at Berkeley as he had claimed;
the University had never heard of this person.

Most of these alternative treatments run on the premise that if you can keep your tree
healthy, you can keep it from getting oak wilt. That is a false statement. Oak wilt does
not work that way.

Oak wilt is a primary pathogen; it does not need an opportunity (such as stress
from drought etc.) to kill your tree. The tree can be perfectly healthy, but oak wilt is
still going to get it, if it is exposed. Other tree diseases, such as oak decline, foliar
OAK WILT Presentation on November 12, 2001                                             Page 10
Robert Edmonson of the Texas Forest Service

fungii problems, hypoxalon etc. are opportunistic diseases. If you keep the tree
healthy, then the tree is not going to get these diseases. This is true for about 99% of
tree diseases. For oak wilt, Dutch elm disease and chestnut blight, tree health has
no bearing on whether the tree will get the disease or not.

Thus, the products represented to prevent oak wilt by keeping your trees healthy
absolutely cannot prevent oak wilt, because it is a primary pathogen. There might be a
use for these “get healthy” tree products, rather than trying to use it as a preventative
measure, such as spraying the trees before they get oak wilt. If the disease comes
through your trees, some of your trees will survive. There is about a 20% survival rate
with oak wilt. Survival means that the tree is still alive. It doesn’t mean that the tree
looks good. In these situations, use these other chemicals to try to nurse the tree back
to health. Using the alternative treatments as a preventative for oak wilt is a waste
of your money, because it is not going to work.

Q: Can the sap beetle infect an oak tree via injuries other than pruning cuts, such
as a branch broken by the wind or a crack in the bark?
A: Yes, trees can be infected by injuries caused by squirrels, woodpeckers, deer,
livestock, etc..

Sometimes where there are many oak wilt disease centers, it can be a valid choice to
stop fighting the oak wilt and work instead on reforestation. Spend your effort in
replanting other trees. Even if you have a lot of wilt surrounding your property, it is still
possible to treat your feature trees, such as those around your house with Alamo. It is
a personal decision.

Trees Recommended for Planting in Hill Country:

Q: What trees are recommended for planting in an area such as Tierra Linda?
A: The Texas Forest Service provides a list of recommended trees (attached).
Select those that grow well in our local conditions of alkaline soil and moderate rainfall.
For example, consider planting cedar elms, bald cypress, Montezuma cypress,
Texas persimmon, and from south Texas, the bird of paradise and huisache, all of
which do well here. Oaks, including live oaks, bur oaks, or Monterrey oaks, are
recommended for replanting behind the disease front after the oak wilt has
moved through the area. When you plant a tree, its roots are not connected to all of
the other oaks that might transmit oak wilt. Root grafting takes a long time to occur.
Thus, the only way the new oak will contract the disease is if a sap beetle infects it with
an oak wilt spore in a fresh wound. Since about 80% of the forest composition tends to
be live oaks, Robert recommends considering planting white oak species to increase
diversity.

The big toothed maple (Acer grandidentatum) is the only maple that will grow well
here. No other maple will do well in our heat and alkaline soil, not sugar maple, not
Japanese maple. It will turn yellow and look terrible all of its life. The sassafras, sweet
gum, magnolia, azalea, loblolly pine also will not grow well here.
OAK WILT Presentation on November 12, 2001                                         Page 11
Robert Edmonson of the Texas Forest Service



Q: Does the shin oak get oak wilt?
A: Yes, all oaks can get oak wilt; some species are more susceptible than others.
Red oaks, blackjack oaks, and Spanish oaks have 100% mortality with oak wilt. White
oaks, including post oaks, bur oaks, lacey oaks, Bigelow or shin oaks, chinquapin oaks,
and Monterrey oaks, while not resistant or immune to oak wilt, tend to tolerate oak wilt
better than red oaks. Robert has seen shin oaks and lacey oaks, and one chinquapin
oak die from oak wilt. Robert does not remember ever having seen a post oak die from
oak wilt.

Q: Where does oak wilt occur in Texas?
A: In over 60 counties statewide, especially in Central Texas, basically along the I-35
corridor, Lubbock, Midland, Houston, Wichita Falls, San Antonio.

Oak wilt is found in 27 states, especially in a band from Wisconsin down to Texas. Oak
wilt is not in Georgia, Florida and Louisiana yet.



               OAK WILT PREVENTION FOR TIERRA LINDA RANCH
               RECOMMENDED BY THE TEXAS FOREST SERVICE

         This Policy was endorsed by the Tierra Linda Board of Directors in 2001.

POLICY:       DO NOT PRUNE OAK TREES FROM FEBRUARY THROUGH JUNE

              ALWAYS IMMEDIATELY PAINT ALL CUTS AND WOUNDS
              TO ALL OAK TREES IN ALL SEASONS

              PAINT PRUNING CUTS EVEN WHEN PRUNING APPARENTLY DEAD
              BRANCHES FROM LIVE TREES

Explanation:
 New oak wilt centers correlate well with human activity, including Spring pruning,
  unpainted pruning cuts, and injuries to trees from string trimmers or heavy
  equipment, such as bulldozers or cedar shears. Several new oak wilt centers were
  started on the Ranch in 2002 from Spring pruning of oaks.

   All oaks are susceptible to oak wilt. Red oaks are rapidly killed, and most infected
    live oaks will die from oak wilt without treatment. Other oaks might not die, however,
    they are likely to be less healthy and look less well than before the infection.

   Unless the wound painting is “immediate”, the sap beetle (only the size of the head
    of a pin) can infect the tree with the oak wilt fungus spores that the sap beetle can
    carry. The practice of doing all the pruning before beginning the painting inevitably
OAK WILT Presentation on November 12, 2001                                        Page 12
Robert Edmonson of the Texas Forest Service

    results in forgetting and missing a significant number of cuts. The Texas Forest
    Service recommends, that if you feel you must prune, then “Cut and paint, cut and
    paint...” for optimum protection.

   While Spring (February through June) represents the highest risk for oak wilt
    infection from pruning cuts, the risk in Tierra Linda is significant throughout the
    year. Sap beetles carry more oak wilt spores in the Spring, but the sap beetles live
    about one year, and thus are always around. Spores can live longer than a year.
    We have so much oak wilt on the Ranch that sap beetles here are more likely
    to carry infectious spores than in less infected areas. Finally, the Texas
    weather can be warm enough in any season, including winter, to have spore-
    carrying sap beetles actively feeding on sap, and transmitting oak wilt spores to oak
    trees. The safest pruning times are on very cold winter days and the next safest
    times are on very hot days in late summer..

   It is necessary to paint pruning cuts on live trees even when pruning “dead” wood
    because at some point the dead wood becomes live wood. It is virtually impossible
    to know where along the branch this change occurs. It is better to be safe than
    sorry.

   Pruning paint in spray cans is rather expensive. An inexpensive, but equally
    effective, alternative is to purchase black automotive undercoating spray paint
    (available in Walmart) or any other spray paint.

The only steps we can control in the oak wilt infection process are:

   Consider not pruning your oak trees. Pruning of oaks is solely for cosmetic
    purposes and provides no health benefit to the tree. “Pruning up” an oak tree
    (removing the lower and inner branches) is actually detrimental to its health.

   If you decide to prune, do not prune or wound oak trees from February
    through June, the highest risk time of year.

   Always immediately paint all cuts and injuries to all oaks in all seasons.

   Do not buy or move firewood from trees that have recently died of oak wilt.
    The fresh wood can be infectious until the wood has dried for several months.

Thank you for taking these precautions with your oak trees. We hope that these steps
will enable you and all of our other homeowners to enjoy our majestic oak trees on the
Ranch for many years to come.

If you think you have oak wilt on your property, often trenching 5’ deep with a rock
saw can prevent the disease from spreading, and Alamo fungicide treatment, at the
proper time, can save oaks within 100’ of the oak wilt-infected trees (Alamo treatment
OAK WILT Presentation on November 12, 2001                                       Page 13
Robert Edmonson of the Texas Forest Service

performed more than 2 years ago is no longer effective). The key to success is
getting expert advice as soon as possible if you think you might have a problem.

Robert Edmonson of the Texas Forest Service will come and evaluate your trees
at no charge. He can be reached at 830-868-7949. Robert has a degree in Forestry
from Texas Tech, as well as 11 years of experience evaluating oak wilt in Tierra Linda.


PBS
12/29/01

				
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