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Post Broadleaf Herbicides for Soybeans
Basagran (bentazon) at 0.5 to 1 qt/A applied POST controls many broadleaf weeds. An oil
additive with Basagran improves weed control. Use oil additive at 1.25% v/v (1 pt/A by
air) or a maximum of 2 pt/A. Basagran at 1 pt/A plus an oil adjuvant has controlled wild
mustard less than 4 inches tall. For volunteer sunflower control, apply 1.5 pt/A to plants
less than 5 inches and 1 pt/A to plants 5 to 8 inches tall. Basagran at 1 qt/A with oil
additive gives good control of common lambsquarters less than 1.5 inches tall and fair to
good control of redroot pigweed less than 1.5 inches tall. Basagran is safe to soybean at
all stages. However, soybean leaf burn occurs occasionally from Basagran but recovery is
good. For Canada thistle control, apply at 1 qt/A when plants are 8 inches tall to bud
stage and make a second application at 1 qt/A 7 to 10 days later. Basagran is commonly
combined with fertilizer micronutrients which may cause incompatibility problems causing
the zinc to precipitate. Chelated zinc materials (black in color) have greater
incompatibility problems than unchelated material (clear). Recommendations to prevent
precipitation are to fill sprayer with water, add Basagran and thoroughly agitate, then
add zinc fertilizer material.
Blazer (acifluorfen) applied POST at 0.5 to 1.5 pt/A controls many broadleaf weeds. The
low
rate will control wild mustard and redroot pigweed but the higher rates are needed for
nightshade, smartweed and common cocklebur. Blazer will not adequately control volunteer
sunflower. Blazer kills primarily by contact action. Apply to weeds 1 to 4 inches tall
that are actively growing and first to second trifoliate soybean. Soybean beyond the third
trifoliate leaf stage may intercept the spray and prevent thorough coverage of the weeds.
Best results are obtained with Blazer applied at maximum daytime temperatures of 70 to 85
F. A NIS (80% active ingredient) generally should be added to the tank at the rate of
0.12% v/v. See the label for additional information on spray additives. Do not apply
within 50 days of harvest or use treated plants for feed or forage.
Cobra (lactofen) at 6 to 12.5 fl oz/A applied POST controls many broadleaf weeds, including lanceleaf sage. Cobra is a contact herbicide and requires thorough spray coverage for good weed control. Soybean beyond the third trifoliate leaf stage may interfere with the spray pattern and reduce the weed coverage. Apply Cobra by ground sprayer delivering at least 20 gpa. Do not apply during periods of crop stress or weed control may be reduced or crop injury increased. Best results are obtained at maximum daytime temperatures of 70 to 85 F. An oil additive at 0.5 to 1 pt/A increases weed control but may increase crop injury. Do not apply within 45 days of harvest or use treated plants for feed or forage. Several tank-mix options are available with Cobra at reduced rates. Cobra can be tank-mixed with Assure II, Select and Pinnacle or Basagran and Pinnacle at reduced rates. Cobra can be aerially applied. See label for use of Cobra to suppress white mold in soybean.
Flexstar (fomesafen + adjuvants) applied POST at 0.75 to 1 pt/A controls common cocklebur, annual smartweed, common lambsquarters, wild mustard, nightshade, pigweed species, common and giant ragweed, sunflower, and Venice mallow. Apply to broadleaf weeds in the 2 to 4 inch stage. Apply 1 pt/A in ND east of I-29 and south of I-94 and in MN south of I-94. Apply at 0.75 pt/A in ND east of Hwy 281 and in MN south of U.S. Hwy 2. Apply with NIS at 0.25 to 0.5% v/v or oil adjuvant at 0.5 to 1% v/v. Oil adjuvant may increase weed control but also increase risk of soybean injury. Flexstar may be applied with POST herbicides labeled in soybean. See label or crop rotation restriction section for additional information.
Pursuit (imazethapyr) at 3 fl oz/A or Pursuit DG at 1.08 oz or 6.67 acres per water
soluble
packet applied POST controls nightshade, kochia, wild mustard and pigweed species and may
control or suppress many other broadleaf weeds not listed on the label. Pursuit has
controlled foxtail, marshelder, Russian thistle, common cocklebur, sunflower, smartweed,
and lanceleaf sage in NDSU field trials. Pursuit may give poor control of Venice mallow,
wild buckwheat, horsetail, common lambsquarters and common ragweed greater than 1 inch
tall. Soil residual from POST applications will not control subsequent flushes of these
weeds. Poor residual control of eastern black nightshade may result when only a small
amount of herbicide reaches the soil surface with POST application. However, even a small
amount of Pursuit may give a reduction in number and intensity of flushes of other weeds.
Pursuit should be applied with an NIS at 0.125 to 0.25% v/v or oil concentrate at 0.5%
v/v, with 28% UAN liquid fertilizer at 4% v/v control. 28% UAN improves control of common
lambsquarters. NDSU research has shown enhanced weed control by using MSO type oil
adjuvants as compared to NIS or some oil additives with or without 28% UAN.
Pursuit at a reduced rate of 2 to 3 fl oz/A can be tank-mixed with Basagran, Cobra or
Pinnacle to increase the spectrum of weeds controlled such as, common cocklebur, common
lambsquarters, common ragweed, Venice mallow, and wild buckwheat. Crop injury from
sequential postemergence applications of Pursuit following Pinnacle is greater than with
either product alone OR the tank-mix of Pursuit plus Pinnacle. In sequential application,
the herbicide applied first reduces the ability of the soybean plant to metabolize the
second herbicide. Pursuit and Pinnacle applied as sequential treatments can result in
severe crop injury. Weeds not controlled by the first herbicide may not be controlled
after the second herbicide is applied. This is particularly important for common
lambsquarters. Weeds that escape control from the first herbicide may be larger than
labeled size by the time the soybean can safely be treated with the second herbicide.
Cultivation before, during or within 7 days after application may also result in reduced
weed control. Cultivation approximately 14 days after application is preferred.
Tank-mixtures of Pursuit with Assure II, Fusilade DX, Fusion, or Select may result in
reduced grass control. Reduced grass control can be avoided by applying the POST grass
herbicide either 1 or more days prior or at least 5 days after Pursuit.
Raptor (imazamox) at 4 fl oz/A POST plus a soil applied grass herbicide or at 5 fl oz/A
alone
POST controls nearly all annual grass and broadleaf weeds in soybean. Grass weeds
controlled are barnyardgrass, crabgrass, foxtail, wild proso millet, field sandbur,
volunteer corn and small grains. Broadleaf weeds controlled are cocklebur, kochia,
lambs-quarters, mustard species, nightshade species, pigweed species, giant ragweed,
annual smartweed, and sunflower. Weeds suppressed are quackgrass, Venice mallow, common
ragweed, sowthistle and Canada thistle.
Raptor is of the same chemistry as Pursuit but has the following differences: 1) More
herbicidally
active, 2) greater grass control, 3) greater broadleaf weed control, 4) increased control
of Pursuit tolerant weed species like lambsquarters and common ragweed, 5) less carryover
following application, and 6) less adjuvant response.
In NDSU field trails, Raptor has controlled weeds listed above plus marshelder, Russian
thistle, and lanceleaf sage less than 1 inch tall. Raptor may give poor control of Venice
mallow, wild buckwheat, horsetail (marestail), large lambsquarters and common ragweed. Low
soil residue of Raptor may not control late germinating weeds or weeds flushes later in
the growing season after rain events.
Raptor should be applied with a NIS at 0.125 to 0.25% v/v or oil concentrate at 0.5% v/v,
each
with 28% UAN liquid fertilizer at 4% v/v. Use of 28% UAN improves control of some weeds
like common lambsquarters. MSO type oil additives should be used when weeds are large
and/or stressed. NDSU research has shown enhanced weed control by using MSO type oil
adjuvants as compared to NIS or some oil additives with or without 28% UAN. However,
Raptor applied with MSO + 28% UAN may result in crop injury at temperatures greater than
88 F and greater than 80% relative humidity.
Crop rotation restrictions the year following Raptor application are much less than with
Pursuit.
However, Raptor carryover is affected by soil pH just as Pursuit. As soil pH increases,
rate of
Raptor degradation increases. At soil pH less than 6.5, rate of breakdown is slow and
injury to
sugarbeet and other sensitive crops may occur if planted in close rotation. See label or
Raptor under the herbicide residue section for information on crop rotation restrictions.
Rezult (bentazon + sethoxydim) at 3.2 pt (1.6 pt/A Rezult G and 1.6 pt/A Rezult B) applied
POST controls most grass and broadleaf weeds in soybean can be applied from emergence to
30 days prior to harvest. Add oil adjuvants at 1 to 2 pt/A. Refer to label or narrative
for tank-mix options. Rezult is priced economically compared to other POST herbicide
programs. Refer to Basagran and Poast sections for additional information.
Select (clethodim) at 4 to 16 fl oz/A or Prism at 8.5 to 34 fl oz/A plus oil additive at 1
qt/A
applied POST controls annual grass weeds and quackgrass. See table in the soybean section
for
rates of Select according to weed species and weed size. Quackgrass can be controlled with
sequential applications at 8 to 16 fl oz/A. Tank-mixing Blazer, Basagran, Cobra or Pursuit
with
Select may reduce grass control. Reduced grass control can be avoided by applying Select
at least 1 day before or 5 days after application of a broadleaf herbicide.
Select is a ACCase mode of action herbicide, similar to Assure II, fenoxaprop, Fusilade,
and Poast. However, research has shown that Select controls many grasses documented
resistant to other ACCase herbicides. No grass has been documented resistant to Select. It
is recommended that Select be used in rotation with herbicides of different modes of
action and in a resistant weed management program.
Pinnacle (thifensulfuron) at 0.25 oz 75DF/A applied POST controls wild mustard, common lambsquarters, and pigweed and suppresses several other broadleaf weeds. Pinnacle should be applied in combination with an NIS at 0.125 to 0.25% v/v or oil concentrate at 0.5% v/v. Further addition of 28% UAN liquid fertilizer at 4% v/v may improve weed control. Pinnacle can be tank-mixed with Basagran, Galaxy, or Storm to increase weed control, including black nightshade. Pinnacle as spray drift or sprayer contamination causes severe injury to susceptible crops such as sugarbeet and sunflower. Thoroughly clean sprayer to prevent contamination of subsequent sprays and injury to susceptible crops. See section on sprayer cleanout.
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