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					Glenn Nice                   2008 / 2009 Indiana Weed Science
Bill Johnson
Vince Davis                               Update
Greg Kruger                 The following article is a tradition with your Purdue Weed Science Team. It is
Paul Marquardt              a companion article with the “Weed Science Updates” that we present around
                            the State of Indiana during the winter meeting season. The Weed Science
Tom Bauman and              Update is a summary of the key points and issues seen around the state in
Tom Jordan                  2008 and a collection of upcoming points of interest to do with weed
                            management and the Agricultural Chemical Industry. It includes information
                            about some of the new herbicides and changes to familiar herbicides in 2008.
Purdue University           Not all of the herbicides mentioned in this article are currently labeled in
Weed Science                Indiana. Labeling of a product will be indicated. Sections of the Weed
                            Science Update will appear in the Pest & Crop Newsletter.

   Products are not           • Herbicide Update              • Weed Update
   considered to be                 - Corn and Soybean             - Update on Herbicide-
  labeled in Indiana                - Forages                         Resistant Horseweed
                                    - Wheat and Small Grains          [Marestail] in Indiana
 if not marked so on          • Weed Science Update and Notes      - Giant Foxtail
      the National                  - European Approval of LL      - Lanceleaf Ragweed
 Pesticide Retrieval                  Soybean                      - Ironweed
                                    - RR/BT Volunteer Corn         - Pricklypear
   System database                  - Herbicide Injury        • Weed Science Tools
 for the Office of the                                             - Non-Crop Select-A-Herb
     Indiana State                                                 - Toxic Plants in Forages
                                                                   - Applied Weed Science
           http://                                     Herbicide Update
                            Kixor [saflufenacil or BAS800] –        velvetleaf, and pigweed/waterhemp
                            BASF:                                   species and thus would fit in both the
                                                                    no-till and conventional-till corn and
                            [Not labeled in Indiana] is a new
                                                                    soybean market. It is anticipated that
                            herbicide from BASF that will be
                                                                    Kixor and Kixor containing
                            labeled for use in corn, soybean,
                                                                    products will be labeled for use for
                            small grains, and tree/nut/vine
                                                                    the 2010 season. BASF has indicated
                            cropping systems. Saflufenacil is a
                                                                    that they will market saflufenacil
Created:   11/15/2008       PPO inhibitor, similar to flumioxazin
                                                                    alone [proposed trade is Sharpen]
Revised:   1/3/2009         [Valor] and sulfentrazone
                                                                    and as premixes with imazethapyr
                            [Authority]. It has shown good
                                                                    [Pursuit] [proposed trade name is
                            foliar and residual activity on
                                                                    Optill] and dimethenamid-P
                            horseweed [marestail], giant and
                                                                    [Outlook] [proposed trade name is
                            common ragweed, lambsquarter,
2008/2009 Indiana Weed Science Update
Authority Assist [3.33 lb ai                     reported by Bayer CropScience to
sulfentrazone + 0.67 lb ai                       increase corn metabolism of
imazethapyr / gal] – FMC:                        isoxaflutole1. Thiencarbazone
                                                 controls grass and broadleaf weeds
[Labeled in Indiana] Last year we                and is an ALS inhibitor2. In trials in
mentioned Authority Assist, a premix             the Midwest, the addition of
of Authority and Pursuit, but at that            thiencarbazone was reported to         
time it was not labeled. Authority               increase giant ragweed and
Assist is now labeled for                        morningglory control over Balance
preemergence use in soybean. It can              Pro alone. Capreno is a premix of
be applied from 45 days before                   Laudis[3.5 lb tembotrione] and
planting to 3 days after planting. To            thiencarbazone.
avoid the potential of seedling injury                                                             Information listed here is
do not apply at cracking. Rates are              Cadet [0.91 lb ai fluthiacet-methyl]              based on research and
from 6 to 12 floz/A depending on soil            – FMC:                                            outreach extension
                                                                                                   programming at Purdue
                                                                        Cadet is a new
                                                                        herbicide labeled          University and elsewhere.
Table 1. Authority Assist rate structure.
                                                                        in corn and
                                   Percent Organic Matter                                          The use of trade names is
                                                                        soybean. The
Soil Texture                                                            active ingredient is       for clarity to readers of
                              1% to 2%                2% to 4%
                                                                        in the PPO, group          this site, does not imply
                             ———-——— fl oz/A ———-———
                                                                        14, family of              endorsement of a
Coarse1                       6 to 8 [4]2         8 to 10 [4 to 5]      herbicides. The            particular brand nor does
Medium                     8 to 10 [4 to 5]       10 to 12 [5 to 6]     PPO herbicides are         exclusion imply non-
                                                                        contact herbicides         approval. Always consult
Fine                       10 to 12 [5 to 6]            12 [6]          and include
                                                                                                   the herbicide label for the
Use higher rates for soils with pH less than 7 and lower rates for pH   herbicides such as
greater than 7 within the rate structure.                               Cobra[2 lb ai lactofen]    most current and update
1 Do not use on sand with less than 1% organic matter.                  and Ultra Blazer[2         precautions and
2 A reduced rate structure is provided to be used in the fall, pre-                                restrictions. Copies,
                                                                        lb ai acifluorfen]. Use
plant, and preemergence in a Roundup Ready soybean system
                                                                        rate will be 0.4 to        reproductions, or
texture and percent organic matter ]                0.9 fl oz/A. It can be tank mixed              transcriptions of this
[table 1].                                          with glyphosate, dicamba, Callisto,            document or its
                                                    Impact and atrazine products. Cadet            information must bear the
The sulfentrazone component has                     can be applied over the top of corn            statement ‘Produced and
shown excellent preemergence                        from the 2nd leaf stage until the corn
control of pigweed, lambsquarter,                                                                  prepared by Purdue
                                                    reaches 48 inches tall. In soybean it
morningglory and good control on                    can be applied over the top from the           University Extension
annual smartweeds and black                         1st trifoliate through full
nightshade. The addition of                         flowering. NIS at 0.25% v/v or COC
imazethapyr will increase control on                at 1% v/v are recommended for an
velvetleaf and foxtail.                             adjuvant.
Balance FLEXX [isoxaflutole +
safener], Corvus [isoxaflutole +                    In a Purdue field trial, Cadet at 0.5 fl
thiencarbazone + safener], and                      oz/A with glyphosate at 16 fl oz/A
Capreno [tembotrione +                              increased control of 4-6 inch
thiencarbazone + safener] – Bayer                   velvetleaf 23% when compared to
CropScience:                                        glyphosate alone at 24 fl oz/A 25
                                                    days after treatment. In studies
[Not presently labeled in Indiana]                  conducted in the Mid-west,
Balance FLEXX, Corvus and                           lambsquarter control ranged from
Capreno will all include a new                      80% to 95% with the use of Cadet +
safener to reduce the potential of                  COC, depending on
injury to corn. The new safener is                  location. Partnering Cadet with
2008/2009 Indiana Weed Science Update
atrazine or glyphosate would provide                           lead to crop injury.
consistency to the control of
                                                               FlexStar [1.88 lb ai fomesafen / gal]
lambsquarter. In a study done in
                                                               – Syngenta:
South Dakota control of common
waterhemp was reported at 93% 15                               [Labled in Indiana] Previous to
days after application. PPO                                    recent supplemental labeling,
herbicides have commonly been used                             FlexStar could be tank mixed at 6-
for waterhemp control; however, it                             12 fl oz/A with glyphosate. New
should be noted that there are several                         supplemental labeling allows rates
                                                               up to 24 fl oz/A in Southern Indiana     Some of the Things You
cases of waterhemp resistance to PPO
herbicides reported in several states.                         [defined as being south of I-70]. In      May Encounter While
                                                               North Indiana, above I-70, a                Reading About
Callisto [4 lb ai mesotrione / gal] –                                                                        Herbicides
                                                               maximum rate of 20 fl oz/A can be
                                                               tank mixed. This is due to potential
                                                                                                       To make things complicated,
[Labeled in Indiana] There have been                           carryover concerns with the
                                                                                                       herbicides have more than one
some changes to the Callisto label this                        FlexStar active ingredient into corn.
                                                                                                       name. One is used to sell the
year. The first change has been to                             FlexStar has a 10 month rotation
                                                                                                       herbicide and one is used to
change the control of burcucumber                              restrictions to field corn and a 12
                                                                                                       know what is in the herbicide.
from ‘partial control’ to ‘control’. The                       month rotation restriction for
                                                                                                       What is in a herbicide is its
label recommendations are 3 fl oz/A                            popcorn when 1 pt/A or more is          “active ingredient” [ai].
to be tank mixed with 0.25 lb ai/A                             used. For individuals wishing to
atrazine with COC and AMS. In a                                plant winter wheat in the fall,         Common name : This is the
study done at Purdue University in                             applications must occur at least 4      term used for its active
North West Indiana, Callisto coupled                           months before planting.                 ingredient. For example,
with a preemergence of Dual II                                                                         glyphosate. Glyphosate can be
                                                               Fultime [2.4 lb ai actochlor + 1.6 lb
Mangum[7.64 lb s-metolachlor] or Lumax                                                                 found in several different
                                                               ai atrazine / gal] and TopNotch
[2.68 lb s-metolachlor + 0.28 lb mesotrione + 1 lb atrazine]                                           products with several names.
                                                               [3.2 lb ai acetochlor / gal] - Dow
controlled burcucumber 91% or 96%,
29 days after treatment respectively3.                                                                 Trade name: This is the name
Burcucumber is a vine that can                                 [Labeled in Indiana] The                that a herbicide is sold under.
germinate as late as August and still                          TopNotch and FulTime labels             Its purpose is to have market
become a problem at harvest.                                   have expanded on the rotation           appeal or recognition. For
Callisto and atrazine provide some                             restrictions. The previous label        example Roundup PowerMax
residual control of burcucumber, but                           specified the rotation restrictions
complete success at harvest may also                           with corn, sorghum, soybeans,           Lb ai : This is an abbreviation
depend on environmental conditions                             tobacco, and wheat. Several crops       for pounds active ingredient.
and soil type. Muck soils provide a                            and situations were not addressed in    Lb ae : Similar to above, this is
challenge to all residual herbicides.                          these rotation restriction sections,    pounds acid equivalent.
Unfortunately this is the case with                            but the labels have been reworked to    Herbicides are formulated in
several residual products that have                            include several other crops. Corn       several different ways to be
activity on burcucumber.                                       can be planted anytime after an         more effective. The acid
                                                               application of either Fultime or        equivalent refers to the amount
A “tank mix with glyphosate” section
                                                               TopNotch, including replant             of the basic active ingredient
has been added to the label for
                                                               situations. Since TopNotch does         without the formulation as a salt
Roundup Ready [RR] corn. This
                                                               not have atrazine, several crops such   etc. This is used for
section allows the use of 3 fl oz/A of
                                                               as alfalfa, sorghum, soybean, sugar     comparisons of herbicides with
Callisto in a tank mix with
                                                               beets, tobacco, sorghum, etc. can be    the same active ingredient.
glyphosate plus AMS at 8.5 to 17
                                                               planted the following spring. Wheat
lb/100 gals. This section warns not to                                                                 fb: followed by. This is used
                                                               has a 4 month restriction with
add COC or UAN to the tank mix if the                                                                  when listing sequential
                                                               TopNotch, which works with the
glyphosate product has a premixed                                                                      applications in a treatment.
                                                               fall seeding of wheat.
adjuvant. If an adjuvant is required
by the glyphosate product it is                                FulTime is a premix containing
recommended to use 0.25% to 0.5%                               atrazine, which changes the rotation
v/v NIS as the adjuvant. Failure to                            interval for several sensitive crops.
follow these recommendations may                               Alfalfa, sugar beets, tobacco and
2008/2009 Indiana Weed Science Update
others require 15 months between              residual activity and will not control
application and planting. This also           weeds not yet emerged. A second
pushes back wheat to 15 months.               preemergence application or a
                                              postemergence applications may
Ignite 280 SL [2.34 lb ai
                                              require tank mixing with a residual
glufosinate / gal] – Bayer:
                                              products for extended control in
[labeled in Indiana] Ignite 280 SL            problematic fields. Sequential   
is similar to Liberty; however, Ignite        applications should be at least 10 to
280 SL contains a higher                      14 days apart. Maximum amount
concentration of the active ingredient        that can be applied on LL corn and
at 2.34 lb ai/gal. Ignite 280 SL is           soybean, in sequential applications,
labeled for crops that are glufosinate        is 44 fl oz/A/growing season. For

Table 3. Comparison of glufosinate and glyphosate on six trouble-
some weeds. [Adapted from Beyers et al. 2002. Weed Technology                               For Free
                                                                                         Herbicide Labels
Herbicide      Rate      Foxtail1   Velvet2   Lambs3      G.Rag4   Cockle5    Morn6
               Lb ai
Glufosinate    0.28        81         92         72           83     81         92
Glufosinate    0.36        88         91         74           90     97         93 
Glufosinate fb 0.28 fb     96         95         90           99     96         96
glufosinate    0.28
                                                                                            Some labels of the
                                                                                          products listed in this
               Lb ae
                                                                                         article are not currently
Glyphosate     0.56        95         92         94           90     76         82
                                                                                         available at the time of
Glyphosate     0.75        96         93         94           95     87         90
Glyphosate fb 0.56 fb      97         97         98           97     98         95
glyphosaste   0.56
1Giant foxtail—averaged over DeKalb IL; Urbana IL 1997 and 1998; Columbia MO
2Velvetleaf—averaged over DeKalb IL 1997-98; Urbana IL 1997.
3Common lambsquarters—averaged over DeKalb IL 1997 and 1998; Urbana IL

1997 and 1998.
4Giant ragweed—averaged over two years at one site, DeKalb IL, 1997 and 1998.
5Common cocklebur—averaged over two years at one site, Columbia MO 1997 and

6Ivyleaf morningglory—averaged over Urbana IL 1998; Columbia MO, 1997-98.

tolerant, known as Liberty Link [LL].         more consistent lambsquarter and
At present, there are LL corn hybrids         velvetleaf control apply between
available and in the future there will        dawn and 2 hours before sunset. The
be LL soybean varieties [see weed             use of soil residual herbicides before
science section below]. Ignite 280
SL can also be used before planting           Table 2. Ignite 280 SL and Liberty rate comparison
or prior to emergence in                         Ignite 280 SL            Glufonsinate        Liberty
conventional soybean or corn. See
                                                      fl oz/A                lb ai/A          fl oz/A
table 2 for a rate comparison
between Ignite 280 SL and                               22                    0.40              31
                                                        26                    0.48              36
Glufosinate does not have any
                                                        36                    0.66              50
2008/2009 Indiana Weed Science Update
crop emergence can reduce the               statement has been added that if
number of crop postemergence                rainfall does not occur within 7 days
applications required or provide a          of application efficacy may be
larger window for later season control.     decreased. If irrigation is available,
                                            apply 0.5 to 1 inches of water to
In LL corn, Ignite 280 SL can be
                                            incorporate herbicide. If neither
applied over-the-top to corn up to and
                                            rainfall or irrigation occurs a shallow
including V5 [five developed collar
                                            cultivation is recommended as soon
leaves] at a rate of 22 fl oz/A. To
                                            as weed emerge. Lexar is not
reduce possible leaf burn Ignite 280
                                            labeled for sweet corn or popcorn.
SL must be applied with ammonium
sulfate [AMS] at 3 lb/A or 1.5 lb/A if      NIC-IT [2 lb ai nicosulfuron / gal] –
temperatures are expected to exceed         Cheminova:                                    Table 4. Control with
85 degrees F.                                                                             Liberty or Ignite 280
                                            NIC-IT has the same active
Ignite 280 SL can be applied                                                              SL
                                            ingredient found in Accent[75%
postemergence at 22 fl oz/A in LL           nicosulfuron]. It is labeled for field corn
soybean from emergence up to but not        [seed or grain] popcorn, and sweat                     Excellent
including the bloom stage.                  corn. NIC-IT can be applied at a
Applications should be made 70 days         rate of 2 to 4 fl oz/A up to V6 or 20                 Giant foxtail
before harvest of soybean. Do not           inch corn. However, the label
graze or cut soybean for hay. Unlike                                                            Black nightshade
                                            recommends early post applications
corn, the soybean section of the            to corn less than 12 inches tall. This                  Cocklebur
Ignite 280 SL label did not have an         maintains applications on small                    Common ragweed
AMS use requirement at the time of          weeds to reduce weed competition
writing this article.                       with corn. Nicosulfuron is excellent                 Giant ragweed
Ignite 280 SL and the LL system             on several annual and perennial                       Jimsonweed
will be marketed as an alternative to a     grasses such as foxtails,
                                            johnsongrass, quackgrass, and                          Smartweed
glyphosate tolerant system. It allows
rotating herbicide modes of action to       shattercane; good to excellent on                         Good
reduce the potential of developing          barnyardgrass and fall panicum, but
                                            weak on crabgrass. Also has good                        Crabgrass
glyphosate resistance biotypes of
weeds. Glufosinate and glyphosate           activity on some broadleaf weeds                      Fall panicum
are both non-selective herbicides and       such as annual morningglory,
                                            jimsonweed, pigweeds, and annual                       Shattercane
slight differences exist in efficacy of
some species [table 3] 5. Glufosinate       smartweeds. For season long control              Seedling johnsongrass
can be slightly less effective on grasses   apply in a program that utilizes a
                                                                                             Annual morningglory
such as yellow foxtail, johnsongrass,       residual herbicide. For best results,
quackgrass, shattercane, and                apply to 2 to 4 inch foxtail and fall                 Burcucumber
barnyardgrass, but is more effective        panicum, 4 to 10 inch quackgrass, 4
                                                                                            Common lambsquarter
on some of the broadleaf weeds such         to 12 inch shattercane, and 8 to 18
as annual morningglory, black               inch rhizome johnsongrass.                               Pigweed
nightshade, and smartweed. Timing           Stout [67.5% nicosulfuron and 5%                        Velvetleaf
is more crucial than with                   thifensulfuron / gal] – DuPont:                        Waterhemp
glyphosate6, 7. However, weed size is
still important with glyphosate; spray      [Labeled in Indiana] Stout is a                           Fair
applications should be done when            premix of Accent and Harmony
weeds are 4 to 6 inches tall.               [75% thifensulfuron]. Stout can be applied
                                            at a rate of 0.5 to 0.75 oz/A to field                Yellow foxtail
Lexar [1.74 lb ai s-metolachlor +           corn with a relative maturity rating
0.224 lb ai mesotrione + 1.74                                                                Rhizome johnsongrass
                                            of 77 days or more. Stout can be
atrazine / gal] – Syngenta:                 applied to corn that up to V5 or 16
 [Labeled in Indiana] New changes to        inches tall. Apply with COC at 1% v/
the Lexar label touch on the                v, MSO at 0.5% v/v, or NIS at 0.25%
incorporation method. A cautionary          v/v. The use of UAN at 2 qt/A or
                                            AMS at 2 qt/A is also required. If
2008/2009 Indiana Weed Science Update
tank mixed with Callisto at a rate            Chateau has been labeled for
greater than 1.5 fl oz, the use of MSO        established alfalfa with a use rate of
is not recommended.                           4 oz/A. Apply to established alfalfa
                                              when growth is 6 inches or less.
Sequence [2.25 lb ae glyphosate + 3
                                              Sequential applications can be made;
lb ai s-metolachlor / gal] –
                                              however, applications must not be
                                              within 60 days of the first     
[Labeled in Indiana] Sequence is a            application and must not exceed 8
glyphosate and Dual II Magnum                 oz/A in one growing season. Do not
premix labeled for corn, soybean and          use any adjuvants or apply with a
sorghum. It can be applied as a fall,         tank mix partner that is formulated
preemergence or postemergence                 as an emulsifiable concentrate [EC].
broadcast application in glyphosate           Chateau can control preemergent
resistant hybrids and cultivars. The          black nightshade, common ragweed,
glyphosate component will not control         jimsonweed lambsquarters,                    For Free
weeds that have not emerged. The s-           horseweed/marestail, pigweed,
metolachlor component will not have           smartweed, velvetleaf and                 Herbicide Labels
activity on emerged weeds, but will           waterhemp. Do not use on alfalfa/
provide some residual activity.               grass mixes or mixes with other 
Residual activity will be decreased if        legumes. Gramoxone Inteon[2 lb
not activated by rainfall or irrigation       paraquat] can be tank mixed to increase              and
within 7 days. The s-metolachlor              burndown activity after cutting.
component can provide good                    Apply within 5 days after cutting and
preemergence control of annual                removal, preferably before 2 inches
grasses yellow nutsedge, black                of new growth. Injury may be                 Some labels of the
nightshade and pigweeds.                      greater on first year alfalfa.             products listed in this
Valor SX [51% flumioxazin] –                  Eptam 20G [20% EPTC] –                    article are not currently
Valent:                                       Gowan:                                    available at the time of
[Labeled in Indiana] A new                                                                       writing.
supplemental label allows the use of          [Pending Indiana approval] Eptam
Valor before field corn emergence in          20G was previously labeled for
no-till or minimum tillage. Apply in          preplant incorporated applications in
the spring 14 to 30 days before               alfalfa for the control of annual and
planting at a rate of 2 oz/A. Valor will      perennial grasses and some
provide residual and some burndown            broadleaf weeds such as henbit,
activity, if used in a burndown               lambsquarter and pigweeds. New
treatment it is recommended to be             label changes will allow the use in
applied with an appropriate                   established alfalfa, previously only
burndown partner such as 2,4-D,               allowed in the western US. In the
Gramoxone Inteon, or a glyphosate             near future [not on Indiana state
product. Do not apply irrigation until        chemist data base at time of writing
field corn is at least at the 2-leaf stage.   article], Eptam 20G will receive
Do not incorporate crop residue.              labeling that will allow the use of 15
Valor has good to excellent                   to 20 lb/A on established alfalfa
preemergence activity of black                where irrigation is available. The
nightshade, lambsquarter, pigweeds,           irrigation will be needed for
horseweed/marestail, and                      incorporation. A 14 day waiting
waterhemp.                                    period is required before harvest.

                                              Milestone [2 lb ai aminopyralid /
                                              gal] and ForeFront [0.33 lb ai
Forages                                       aminopyralid + 2.67 lb ai 2,4-D / gal]
Chateau [51% flumioxazin] –                   - Dow AgroScience:
Valent: [Pending Indiana approval]:
                                              [Labeled in Indiana] Milestone
2008/2009 Indiana Weed Science Update
and ForeFront are labeled for                Milestone label states “Do not use
permanent pastures, conservation             aminopyralid-treated plant
reserve program, wildlife areas, and         residues, including hay or straw
several non-crop areas. The active           from treated areas. . . in compost or
ingredient aminopyralid is good to           mulch that will be applied to areas
excellent on several thistles and annual     where commercially grown
and perennial weeds such as common           mushrooms or susceptible      
ragweed, horseweed, dock species, and        broadleaf plants may be grown.”
some buttercups. Aminopyralid is in
the herbicide family of pyridine         Movement in the animal -
                                         Herbicides that have these active              Employ company to
carboxylic acids. Other herbicides that                                                  apply herbicide to
have active ingredients that belong to   ingredients generally do not have
                                         grazing restriction for non-lactating                 stump
this family of herbicides are Crossbow
[triclopyr + 2,4-D], Stinger             animals but the labels will generally
[clopyralid], Transline [clopyralid],    require the animals be grazed on
Tordon [picloram]. Two issues with       non-treated forages for 3 days
the use of these herbicides should be    before the animals can be moved to
taken into account. Both of these issues pastures of sensitive crops. The                 Stump is chipped
have to do with the chain of events afterreason for this is that the herbicide             and discarded
an application of these products. When   simply passes though the animals
using these products and other           on the food they consume. The
herbicides, it is important to consider  herbicides in this family are not
                                         altered as they pass through the
what is going to be done to the site after
application. Not only do we have to      animal’s body and can be found in
                                         the urine and manure produced by               Neighbor notices the
consider this for rotational aspects but                                                 chipped wood and
for environmental reasons. In some       the animal. If the animal is moved
                                         from a treated pasture or fed feed             asks family member
cases it is also important to consider                                                   if they can use the
what the vegetative material sprayed is  from a treated pasture then moved
                                         to a pasture with legumes or other                     chips
going to be used for after application.
                                         sensitive broadleaf crops, injury of
Residual activity – Pyridine             those sensitive crops will occur.
carboxylic acids can remain in soil and  One way to think of this is if the
plant residue for some time. The half-   animal has been feeding on treated
life of aminopyralid, clopyralid,        feed, when the animal relieves its               Sure, why not.
picloram and triclopyr are               self, it is essentially making a               Family member does
approximately 34.5, 40, 90 and 30        herbicide application. Rotation                  not know about
days, respectively8. This is dependent   restrictions state that to switch                  application
on the soil and environment. Picloram from pasture to a sensitive crop, a
has been reported to have a half-life of one year period has to occur before
300 days in some conditions. This        planting. The use of a bioassay is
leads to the need to know what is going recommended. It might be safe to
to happen to the land and plants where assume that if you move cattle from
these herbicides could be applied.       a treated pasture to a non-treated             The wood chips are
                                         pasture you may be making a                    used as mulch at the
In the scenario to the right, an         herbicide application, and the one              base of neighbors
application is made by a company or      year rotation restriction could                    prize roses
one family member to an old stump        imply even though you have not                  Roses are injured
then chipped, then the mulch is sold to applied the herbicide directly to the
a third party. The third party, possibly pasture. In one case experienced in
a neighbor, uses the mulch not realizing 2008 in Indiana, cattle were fed
                                                                                     Figure 1. Example of
that herbicide was used and that         treated feed, and then moved to a           where problems can occur
residues may still be in the mulch. It   grass/legume mixed pasture where            with residual products
has happened. The same situation can     the legumes started to show growth
happen with chipped shrubs and trees     regulator injury.
that have originally been sprayed. The
2008/2009 Indiana Weed Science Update

Weed Science Update and Notes              Transgenic volunteer corn plants
                                           that escape glyphosate treatments
                                           are not only economically damaging,
European Approval of LL                    but these plants are providing
Soybean – Liberty Link [LL] corn           increased selection pressure on
has been around for some time. The         insects such as the western corn
trait LL allows over the top               rootworm [WCR] by exposing WCR 
applications of glufosinate, the active    to B.t. toxins outside of mandated
ingredient in the herbicide Liberty        insect resistance management or
and now Ignite 280 SL [see above           refuge programs. Preliminary data
herbicide section]. Although, LL           has shown that more WCR emerge
soybean had been approved in the US        from volunteer corn plants
and Canada, it was not approved in         expressing B.t. than non-B.t.
Europe. In September the European          volunteer corn plants, indicating that
Commission approved the import LL          the toxin, while still present, may be
soybean for food and feed. The use of
LL corn and soybean will be marketed
as an alternative to glyphosate tolerant
systems. It is a different mode of
action that can be used to lower the
selection pressure for herbicide
resistance by providing another mode
of action. At present there are no
cases of resistance reported9.
Glufosinate inhibits the production of
glutamine synthetase having good to
excellent control on some annual
grasses and several broadleaves [Table
RR/BT Volunteer Corn -
Transgenic volunteer corn expressing
herbicide resistance [HR] traits is a
significant problem weed in corn/          doing little to inhibit the
soybean rotational systems. This issue     development of WCR. The simple
is particularly timely due to the          solution to this problem is to scout
increasing prevalence of stacking both     for volunteer corn, especially in
herbicide and insect-resistant [mainly     soybean fields following multiple-
B.t.] traits into the same genetically-    trait transgenic corn. Where corn is
modified plant. With increased             present, the addition of grass
adoption of transgenic corn                herbicides in combination with
technology containing multiple             glyphosate should take care of the
transgenic traits, more growers are        problem.
experiencing increases in the number       Herbicide Injury
of volunteer corn plants in soybean
surviving regular applications of          Corn injury and problems – This
glyphosate10. Through greenhouse           past year has not been an easy year
dose response studies, these volunteer     for corn growers in some parts of
corn plants have consistently              Indiana. A spring that delivered too
expressed resistance to glyphosate at      much rain11, so much so that parts of
levels similar to that of their parental   the state were under water, then
transgenic plants. In addition, many       when the rain stopped, high
of these transgenic volunteer corn         temperatures and drought doubled
plants surviving glyphosate treatments     the crop stress. When it came to
are exhibiting some insect resistance      corn there were two interesting
with the expression of B.t. traits.        problems seen in the Plant & Pest
2008/2009 Indiana Weed Science Update
                                              Diagnostic Lab
                                              /ppdl/]. The first,
                                              were random plants
                                              with curves in the
                                              stems, some as    
                                              pronounced as to
                                              produce a right angle
                                              in the stem [figure 1].
                                              At first glance the
                                              diagnosis of possible
                                              growth regulator
                                              injury could be
                                              deduced. Growth
Figure 2. Right angled stems seen in corn.    regulators can cause
                                              such abnormalities
                                              such as ‘onion leaf’ and
                                              curvatures of the stem
                                              [figure 2]. Different
                                              conditions, and
                                              malfunction can
                                              produce a variable
                                              response to growth
                                              regulators. However,
                                              in some of these cases
                                              growth regulators were
                                              not suspected to be the
Figure 3. Slight curvature of the stem.       prime driver for this,
                                              partially due to the fact
                                              that there was no
                                              pattern of injury. In
                                              one case it was only
                                              the male line that
                                              showed this effect.
                                              European corn borer
                                              has been reported to
                                              cause bending or
                                              breaking of stems, in
                                              some cases “goose
                                              necking” can be
                                              associated with
                                              European corn borer
                                              when lodging occurs.
                                              The “goose neck”
                                              appearance occurs as
                                              the plant tries to right
                                              itself. Splitting the
                                              stems can identify the
                                              presence of tunneling.
Figure 4. Submitted sample showing “pinched   There was no evidence
ears.”                                        of tunneling. Could
2008/2009 Indiana Weed Science Update

this symptom be due to other                          Weed Update
factors? There were no good
                                           Update on Herbicide-Resistant
answers found for this situation.
                                           Horseweed [marestail] in
The second issues seen in larger           Indiana - It has been awhile since
degrees this past year were ears           we have written much about
showing abnormalities such as              glyphosate-resistant horseweed in
“pinched ears” [Figure 4] and nubbin       Indiana. It was first collected in a
ears [blunt ears]. “Pinched ears” are      Roundup Ready soybean fields in
                                           southeastern Indiana in the fall of
a result of a reduced number of
                                           2002. This weed was a concern for
kernel rows and nubbin ears are a          many soybean farmers and was the
result of reduce ear elongation.           subject of many extension articles for
Diagnosing herbicide injury is a           a few years after that first
precarious task at harvest. With no        documentation; much information
foliar symptomology to rely on to          can still be found on our Horseweed/
support or rule out herbicide              Marestail website. We conducted an
problems it is very difficult to put the   extensive in-field survey throughout
whole blame on a herbicide. Late           Indiana in the fall months from 2003
applications of ALS herbicides over        through 2005 to understand the
                                           distribution and frequency of this

 Figure 5. Indiana counties colored in green had horseweed/marstail popula-
 tions with plants resistant to chlorimuron [left] glyphosate [middle] and both

the top after v6 can induce pinched        weed problem. We found glyphosate
ears in corn. The cause of nubbin          -resistant horseweed infested over
ears has been associated with stress       1/3 of all soybean acres in the
                                           southeastern region of the state. We
applied to corn in the V8 to V12
                                           also found glyphosate-resistant
stages12. This could be herbicide          horseweed in the other regions of the
related or be sudden changes in            state as well but at a frequency of less
temperature and growing conditions.        than 2% of randomly sample fields.
A recent article by Neilson, Wise,         A number of previous articles
and Gerber suspect adjuvants may           suggested recommendations for the
have some impact13.                        control of glyphosate-resistant
2008/2009 Indiana Weed Science Update
horseweed, and many farmers and             horseweed in the rosette stage or
advisers have learned how to control        under 4 inches of stem elongation is
this weed over the last six years.          the best timing for adequate control.
However, during our late summer and         This is likely to occur in early April
fall travels throughout the state, it has   for fall emerging plants and late-
been obvious that horseweed is still a      April to the middle of May for spring
persistent and challenging weed for         emerging plants. Applying 2,4-D to
many soybean farmers. It also               small plants provides the best
appears this problem may be                 control and should also allow plenty
increasing in the other three regions       of time to follow soybean preplant
of the state; although, we have not         restrictions on the 2,4-D label. If
continued late-season in-field surveys      horseweed becomes larger than 4
to make that statement conclusive.          inches, higher rates and tank-mixing
The persistence and constant invasion       other herbicides will be more critical
on horseweed to new areas is not            to achieve adequate control.
surprising because horseweed can
produce hundreds of thousands of            More information about horseweed
seeds. Worse yet, each of these seeds       distribution in Indiana as well as
have an appendage [called a pappus]         management recommendations can
like dandelion that allow them to be        still be found at:
blown by the wind and infest                [
unsuspecting adjacent no-till fields.       weedscience/marestail/index.htm].
                                            Another very useful resource
In addition to investigating glyphosate     available online is a publication titled
-resistant horseweed, we recently           “Biology and Management of                 Figure 6. Lanceleaf
completed herbicide screens on all of       Horseweed” produced by Purdue              ragweed [Britton,
our collected horseweed populations         University, The Ohio State                 N.L. and A. brown.
for resistance to 2,4-D and                 University, and the University of          1913. An illustrated
acetolactate systhesis inhibitor [ALS]      Illinois.                                  flora of the Northern
herbicides. We found horseweed
                                            Other glyphosate resistant weeds           United States,
populations with plants resistant to
chlorimuron in 30 Indiana counties          include giant ragweed and there are        Canada and the
[Figure 5]. Several of these counties       common ragweed populations under           British Possessions]
also had populations with glyphosate-       suspicion.
resistant horseweed, but fortunately        Foxtail - Giant foxtail [Setaria
we found few populations resistant to       faberi] is a problematic weed in both
tank-mix combinations of the two            soybean and corn. Previous work
herbicides. Therefore, if you must          has indicated that some populations
control horseweed at the                    of G. foxtail are resistant to ALS
postemergence soybean timing and            inhibitors. In Indiana, due to the
you suspect either glyphosate or ALS-       large amount of acreage planted to
resistant plants in your field, tank-       glyphosate-resistant soybean each
mixing these herbicides may still be a      year [> 90%] and the use of
viable option. However, as we have          glyphosate as the primary herbicide
always recommended, the best                in these fields, the issue of G. foxtail
management practice with horseweed          developing resistance to glyphosate
is to control plants when they are          is a serious concern. In 2008,             Figure 7. Lanceleaf
small and prior to planting your            greenhouse glyphosate dose-
soybeans. The good news is, we did                                                     ragweed [Missouri
                                            response research was conducted on
not find any populations that were                                                     Plants,
                                            7 G. foxtail populations collected
resistant to 2,4-D. We did find some        from 7 different sites around              www.missouriplants.
of our horseweed populations had a          Indiana. We found no significant           com/Greenalt/
remarkable increase in tolerance to         difference between the 7 populations       Ambrosia_bidentata
2,4-D though. This leads to some            and their response to increasing           _page.html
cause for concern about over relying        doses of glyphosate. This has led us
on 2,4-D. Applying 2,4-D on                 to conclude that G. foxtail has not yet
2008/2009 Indiana Weed Science Update
developed resistance to glyphosate,       pastures throughout the US. They
but this weed should remain on the        belong to the genus Vernonia spp.
“watch list” as a possible candidate in
the future.                               The use of glyphosate has been
                                          reported to have good to excellent
Lanceleaf ragweed [Ambrosia               control of ironweed. However,
bidentata]: Lanceleaf ragweed, as the     control with glyphosate may provide    
name suggests, is a relative of           variable results. In a study by Peters
Indiana’s number one weed, giant          and Lowance [1979] control was
ragweed. At first appearance and for      reported to range from 2% to 88%
that matter second appearance,            depending on year17. The authors
lanceleaf ragweed does not appear to      attributed low control to lack of
look anything like giant ragweed.         rainfall and the poor growing
However, these two native plants have     conditions of those years. For
been reported to hybridize14. The first   sufficient efficacy on perennial
difference is stature; lanceleaf          weeds, glyphosate requires the weed
ragweed maxes out at about 3 feet tall.   to be translocating efficiently.
Lanceleaf ragweed has a fairly hairy      Glyphosate efficacy is increased
appearance, and its leaves are lance      when weeds are growing in good
shaped, single nerved and do not have     conditions. Glyphosate can only be
petioles. Leaves are 1 to 3 inches long   applied as a directed application,
and 2.7 to 0.3 inches wide. Leafs can     such as a wiper application or as a
have 1 or 2 sharp lobes. Flowers are      spot application for it can injure or
arranged in tight spikes 3 to 7 inches    control desired grasses and legumes.
long and have a distinctive lobe that
appears like a bract [figure].            Herbicides containing the active
Lanceleaf ragweed blooms in July to       ingredients dicamba [Banvel,
September15.                              Clarity], 2,4-D [many], and triclopyr
                                          [Garlon 4 Ultra, Garlon 3A] were
Next to giant and common ragweed,         investigated for the control of tall
lanceleaf ragweed is a small player       ironweed3. Dicamba alone did not
and has not typically been a problem      control tall ironweed greater than
in Indiana, but can it can be found in    76% and had 81% or greater
the odd pasture and in waste area.        regrowth. The use of triclopyr alone
Rice and Stritzke reported at least a     or triclopyr plus 2,4-D provided
94% decrease in density when using        control 91% and up. In the triclopyr
2,4-D at 0.5 lb ai/A16. Both Banvel       alone or with 2,4-D, regrowth did not
and Cimarron Max have lanceleaf           exceed 39% of the original stand.
ragweed on their labels as being          Two years after the study, control of
controlled. Banvel should be used at 1    tall ironweed was maintained above
pt/A. Cimarron Max is a co-pack and       90%.
should be applied at 0.25 oz/A of part
A and 1 pt/A of part B.
                                           Table 5. Pricklypear control with and without mowing.
Ironweed [Vernonia spp.]:
Ironweed has not been a stranger to        Herbicide treatment                      Rate                    5% Injury
Indiana’s pastures, but this year it       Tordon RTU—Injection1                    1 ml/cladode               69 a
appeared to be more common than in
the past. They are often 3 to 5-foot       Crossbow                                 4 qt/A                     34 b
tall with purple inflorescence,            Crossbow + mowing                        4 qt/A                    20 bc
although they can reach heights of 10
feet tall. In a pasture that has been      Roundup PowerMax + AMS                   27 fl oz/A                  5c
heavily grazed, they are often the only    Roundup PowerMax + AMS + Mowing 27 fl oz/A                           4c
plant of substantial size left. The
ironweeds are a group of native            Forefront + NIS                          2 pt/A                      1c
perennials that can be troublesome in      1Tordon   was injected into each cladode at 1 ml/injection
2008/2009 Indiana Weed Science Update

Crossbow, a premix of triclopyr and        can complicate things, for pricklypear
2,4-D can be used to control tall          often is a problem on Indiana’s more
ironweed at 2 qt/A broadcast or in a       sandy soils. There has been some
hand-held applicator at 1% v/v.            report of herbicides with the active
Milestone at 5 to 7 floz/A or              ingredient triclopyr having some
ForeFront at 2 to 2.6 pt/A will have       activity on pricklypear.
good activity on ironweed5.                There has not been a large body of
[information previously appeared as        research on pricklypear’s control. In a
a Picture of the Week, P&PDL:              demonstration conducted in Indiana,           6 treatments were applied on July 10.
weeklypics/9-22-08.html].                  Ratings were taken July 22 and
Pricklypear [Opuntia spp.]: This           October 6. Ratings were based on
group of plants have had a rich            percent of dead material or injury to
history in the US. Watch out, this         live material. Dead material could be
armed plant bites back. Touching           identified in plots. Due to the
this plant will more than likely leave     sporadic nature of the populations,
you in a cranky mood. Small yellow         comparisons to a non-herbicide check
brown barbed hairs called glocides         were inconclusive. The October 6th
will end up everywhere causing             rating is presented in table 5.
welting and discomfort. Each               The injected Tordon RTU appeared to
segment or cladode of pricklypear          be the most damage to the pricklypear
can take root to form a new plant.         plants at 69%. However, the amount
For more information on the prickly        of effort put into injecting each
pear in Indiana please see “A Prickly      cladode in a large infestation would
Situation That Pricklypear” on the         not make this treatment practical. If
Weed Science web page.                     that amount of effort was required,
Pricklypear can be troublesome in a        then manually removing plants and
pasture or waste areas. In one             burning them would be about equal to
reported case it was causing               using the injection method. Mowing
complications in a cemetery. Control       was included with Crossbow and
can be difficult. Mowing alone has         Roundup PowerMax to investigate the
promoted its growth. Plant parts           possibility that applying herbicide
that become separated during               treatments would inhibit cladode
mowing take root and form new              rooting and plant growth. Mowing
colonies. Plants can be cut below the      followed by the application of
soil level with dandelion fork then        Crossbow did have similar injury to
burned. In a study conducted in            Crossbow alone.
Texas with tulip pricklypear [O.
phaeacantha], prescribed burning
over three years controlled plants                Weed Science Tools
75%, 81%, and 68% when plants              New tool for non-crop weed
were 1-10, 11-25, and over 25              management, Select-A-Herb:
cladodes large18.                          Some of you may have used Select-A-
In many cases people will try and use      Herb for row crops in the past [http://
2,4-D to control pricklypear. This is
generally ineffective. Herbicides          herbsel/]. If you have not, Select-A-
with the active ingredient picloram        Herb is a free web based program that
are most often cited to control            lists herbicides and the weeds that the
pricklypear. Although most often           herbicides are effective on. The
effective, products with picloram are      program and data base have been
not all labeled in the state of Indiana,   described as “a point in the right
and many state that the product            direction.” It is not meant to be the
cannot be used on sandy soils. This        final say in what herbicide is best
                                           suited for the situation, experience,
2008/2009 Indiana Weed Science Update

knowledge of herbicide use and the          label. The Select-A-Herbs are not
herbicide label are required for that,      the label and the label should always
but it is a source to start with to get     be read and followed when using
an idea of the options available. The       pesticides.
row crop Select-A-Herb provides a
                                            Toxic Plants in Forages: Certain
drop down menus of the weed, crop,
                                            plants produce toxins that can
or herbicide. Selecting from these                                         
                                            decrease the fitness of livestock. In
drop down menus will provide the
                                            severe cases animals can die. The
options available. The new Non-
                                            Plant & Pest Diagnostic Lab at
Crop Select-A-Herb will provide
                                            Purdue University often receives
                                            samples from around the state of
The Non-Crop Select-A-Herb is               plants that have been associated with
backed by a data base of 25 thousand        possible poisonings. In 2007, 13
records and provides information on         samples were submitted to the Plant         For Free
over 1000 labeled weeds. This new           & Pest Diagnostics Lab where
data base will give herbicide options       suspected poisoning of animals           Herbicide Labels
with rates, timing, weed sizes, and         occurred. Eight of these had plants
notes from the label to help in the         that are known to be toxic to  
selection process. This information         livestock present. In 2008, 18
will be organized in an easy to print       samples were submitted; however,                    and
handout. Non-Crop Select-A-Herb             only 2 had plants that were identified
will not provide you with a label, but      as toxic. Identification and control
will provide a link to the CDMS             of these plants are an important
search web site that will provide a         aspect of pasture management.               Some labels of the
                                                                                      products listed in this
                                                                                     article are not currently
                                                                                     available at the time of

                       The Guide to Toxic Plants is 26 pages of
                       information about the plants that if you have
                       pasture you should be aware of. Each plant has
                       illustrations and pictures to help with its
                       identification and control recommendations. This
                       publication can be viewed on line [http://
                       ToxicPlants08.pdf] or bought through Purdue
                       Media Distribution for $4 a copy

                       The third edition of "Applied Weed Science" is now
                       available. This edition of the text book by Merrill A.
                       Ross and Carole A. Lembi provides updates on all
                       management methods, including herbicide
                       technology and resistance, and new chapters on
                       weed ecology and plant invasions. This new
                       edition incorporates the principles of plant
                       management to both crop weeds and invasive
                       plants [including woody perennials] in natural
                       systems. This text book can be purchased at
              for $74.66 .
2008/2009 Indiana Weed Science Update


    1.    Farm and Range Guide. New Weed Control Products for Corn. [http://

    2.    Philbook, B.D. and H. Santel. 2007. Thiencarbazone-methyl: a new molecule
          for pre and postemergence weed control in corn. NCWSS PROC. 62:150.
    3.    Johnson, B. 2005. Annual Research Report. Number 026. [http://
    4.    Wiesbrook, M.L., W.G. Johnson, S.E. Hart, P.R. Bradley, and L.M. Wax.
          2001. Comparison of weed management systems in narrow-row, glyphosate-
          and glufosinate-resistant soybean [Glycine max]. Weed Technology 15:122-
    5.    Beyers, J.T., R.J. Smeda, W.G. Johnson. 2002. Weed management
          programs in glufosinate-resistant soybean [Glycine max]. Weed Technology
    6.    Steckel, G.J., L.M. Wax, F.W. Simmons, and W.H. Phillips, II. 1997.
          Glufosinate efficacy on annual weeds is influenced by rate and growth stage.
          Weed Technology. 15:484-488.
    7.    Loux, M.M., A.F. Dobbels, J.M. Stachler, W.G. Johnson, G.R.W. Nice, and
          T.T. Bauman. 2008 Weed Control Guide. WS-16.
    8.    Weed Science Society of America. 2007. Herbicide Handbook. 9th ed. pp. 331
    9.    Heap. Accessed Oct. 10 2008. International Survey of Herbicide Resistant
          Weeds. []
    10.   Davis, V.M., P.T. Marquardt, and W.G. Johnson. 2008. Volunteer corn in
          northern Indiana soybean correlates to glyphosate-resistant corn adoption.
          Online. Crop Management. doi: 10.1094/CM-2008-0721-01-BR.
    11.   Steeves, S.A. 2008. Rain and flooding likely to continue. Purdue University
    12.   Thomison, P. and A. Geyer. Abnormal Corn Ears. The Ohio State University.
    13.   Nielson, B., K. Wise and C. Gerber. Accessed Dec. 2008. Arrested Ears
          Resulting From Pre-Tassel Applications of Pesticide & Spray Additive
          Combinations. [
    14.   Lee, Y. S. and D.B. Dickinson. 1980. Field Observations on Hybrids between
          Ambrosia bidentata and A. trifida [Compositae]. American Midland
          Naturalist 103:180-184
    15.   Brown, N. and A. Brown. 1970. An Illustrated Flora of the Northern United
          States and Canada: Volume 3. Second ed. p. 341.
    16.   Rice, C.K. and J.F. Stritzke. 1989. Effects of 2,4-D and Atrazine on Degraded
          Oklahoma Grasslands. Journal of Range Management 42:217-222.
    17.   Peters, E.J. and S.A. Lowance. 1979. Herbicides for Renovation of Pastures
          and Control of Tall Ironweed [Vernonia altissima]. Weed Science 27:342-345.
    18.   Bunting, S.C., H.A. Wright, L.F. Neuenschwander. 1980. Long-term effects of
          fire on cactus in the southern mixed prairie of Texas. Journal of Range
          Management. Vol. 33:85-88.

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