PrePlant Herbicide Weed Control in Soybeans

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Source: North Dakota State University

Authority (sulfentrazone) at 4 to 5.33 oz/A applied PPI or PRE controls most annual small-seeded broadleaf weeds, such as, kochia, pigweed species, lambsquarters, nightshade, smartweed, and biennial wormwood and may suppress other weeds like buckwheat, mustard, ragweed, Venice mallow, and Russian thistle. Authority controls ALS resistant weeds, provides little grass, and no perennial weed control. Adjust rate for soil type. Authority provides excellent burndown weed control and may be applied up to 30 days prior to planting but use the higher rate in the appropriate rate range. Authority can tank-mixed with most PPI/PRE herbicides registered in soybean. NDSU research has shown excellent weed control in many different environments throughout the Great Plains region. However, consistent control of sensitive broadleaf weeds and control of grass and marginally controlled broadleaf weeds requires at least 0.75 inch rainfall prior to weed emergence. Authority will leave a residue in soil for more than one year. Refer to label or crop rotation restriction section for additional information.

Lasso at 2 to 3 qt 4E/A applied PPI or PRE, Dual at 1.5 to 3 pt 8E/A applied PPI or PRE (NOT EPOST), Frontier at 1 to 2 pt 6.0E/A applied PPI, PRE, or EPOST up to third trifoliate, or Axiom at 7 to 13 fl oz/A or Domain at 9 to 16 oz WDG/A applied PPI or PRE control annual grass and some broadleaf weeds, including redroot pigweed, black nightshade, and common lambsquarters but are ineffective against wild oat. Apply the higher rate on clay soils high in organic matter. Soybean has good tolerance and incorporation improves consistency of weed control. Dual may be surface applied or incorporated in the fall after October 15 but before ground freezes or applied in the spring. Herbicides are registered for tank-mixing with several herbicides. Frontier can be applied EPOST with Pursuit. Do not ensilage soybean or feed forage, hay or straw from soybean treated with Lasso.

Lexone/Sencor (metribuzin) at 0.25 to 0.5 lb 75DF/A controls annual broadleaf weeds, especially wild mustard. The rate applied is important. Consult the label for the proper rate based on soil type, pH, and % organic matter. Some soybean varieties are susceptible to metribuzin; consult label for list of susceptible varieties. Soybean injury can be reduced by using herbicide combinations with lower rates of metribuzin. Metribuzin is registered as a tank-mixture with Lasso, Sonalan, Dual, Prowl and trifluralin.

Prowl/Pendimax (pendimethalin) at 2 to 3 pt/A EC or 0.83 to 2.5 lb DG applied PPI controls annual grass and certain broadleaf weeds. The high rate should be used on heavy clay soils. Prowl is registered as a tank-mixture with Lasso, Lorox, Dual, and metribuzin. See herbicide residue section.

Pursuit Plus (imazethapyr + pendimethalin) at 1.8 pt/A applied PPI controls most annual grass and broadleaf weeds. ND state labeling allows use in ND south of State Highway 2 at a reduced rate of 1.8 pt/A which is 75% of the full labeled rate. Pursuit Plus at 1.8 pt/A contains the equivalent of Pursuit at 3 fl oz/A or 1.08 oz WDG/A plus 1.75 pt/A of Prowl. Add additional Prowl at 1.75 pt/A for more consistent weed control. Thoroughly incorporate into the top 1 to 2 inches of soil. Refer to paragraphs on Pursuit and Prowl for additional information on use and restrictions.

Python (flumetsulam) at 0.8 to 1.33 oz 80WDG/A applied PPI or PRE will control many annual broadleaf weeds in soybean. Python is the Broadstrike component in the commercial premixes available as Broadstrike + Dual or Broadstrike + Treflan, and also a component in corn premixes Hornet, Scorpion III, and Accent Gold. Python is active on small-seeded broadleaf weeds like nightshade, pigweed, kochia, biennial wormwood, common lambsquarters, mustard, annual smartweed, Venice mallow, and Russian thistle. Python gives poor control of large-seeded broadleaf weeds like common and giant ragweed.

As with all soil applied herbicides, Python requires soil moisture for optimum weed control. Good soil moisture and timely rains shortly after application are needed to ensure adequate herbicide performance. Python is also strongly affected by soil pH. High soil pH increases herbicide activity and increases speed of herbicide degradation, but also increases risk of crop injury. Excellent broad spectrum weed control may occur when applied on soils with above 7.5 pH, when significant precipitation occurs after application, when rates are based on soil texture and organic matter content, and under light to moderate weed infestations. Some stunting may occur under poor growing conditions on soils with pH greater than 8.0.

Use the higher rates on medium to fine textured soils and the lower rates on coarse textured soils. PPI applications may be made 30 days before planting. Incorporate uniformly into the top 2 inches for PPI applications. Do not apply to soils with a pH greater than 8.0 as crop injury may result. Python is registered as a tank-mixture with most soil applied herbicides labeled in soybean. See Python under the Herbicide Residue section for information on crop rotation restrictions.

Sonalan (ethalfluralin), Prowl and trifluralin are dinitroaniline herbicides applied PPI for control of annual grasses and broadleaf weeds except wild mustard, common cocklebur and sunflower. Requirements for proper timing and depth of incorporation differ for each herbicide. Sonalan (ethalfluralin) at 1.3 to 3.5 pt/A applied PPI controls annual grass and certain broadleaf weeds. The low rate should be used on coarse-textured, sandy soils. Incorporate in the top 2 to 3
inches of soil within 2 days of application. Incorporation of Sonalan 10G can delayed 3 to 5 days after application. Sonalan is registered as a tank-mixture with most soil PPI and PRE herbicides labeled in soybean including Dual, Lasso, or Lexone/Sencor. Sonalan has less soil residue than trifluralin but is more active at comparable rates than trifluralin.

Trifluralin at 1 to 2 pt 4E/A applied PPI controls annual grass and certain broadleaf weeds. Set the implement 4 to 6 inches deep to uniformly mix trifluralin in soil. Trifluralin incorporation may be delayed up to 24 hours if applied to a cool, dry soil and if wind velocity is less than 10 mph. Do not plant soybean deeper than 2 inches. Trifluralin is registered as a tank-mixture with Lasso, Dual, and metribuzin. See herbicide residue section.

Broadstrike + Treflan (flumetsulam + trifluralin) at 1.5 to 2.25 pt/A of premix product or 0.05 to 0.07 of the Broadstrike/ Python component + 0.64 to 0.96 lb/A of the trifluralin component applied PPI will control most grass and broadleaf weeds in soybean. Broadstrike is formulated alone as Python. See Python in this section for more information on flumetsulam. NDSU research has shown excellent weed control from Broadstrike + Treflan on most grass and broadleaf weeds ONLY after receiving adequate rainfall within the first 7 to 10 days after application. Broadstrike + Treflan will not control large-seeded broadleaf weeds. Refer to paragraph on Python for additional information on Broadstrike (flumetsulam).

Use the higher rates on medium to fine textured soils and the lower rates on coarse textured soils. PPI applications may be made 30 days before planting. Instructions for incorporating Broadstrike + Treflan are the same as incorporation of Treflan alone. Incorporate uniformly into the top 2 inches for PPI applications. Do not apply to soils with a pH greater than 8.0 as crop injury may result. Broadstrike + Treflan is registered as a tank-mixture with glyphosate, Gramoxone Extra, and Lexone. See Broadstrike + Treflan under the Herbicide Residue section for information on crop rotation restrictions.

FirstRate (cloransulam) applied at 0.6 to 0.75 oz 80WDG/A PPI or PRE controls common cocklebur, common lambsquarters, horseweed (marestail), pigweed species, annual smartweeds, common and giant ragweed, sunflower, and velvetleaf. FirstRate gives poor nightshade control.

As with all soil applied herbicides, FirstRate requires rain to activate the herbicide for adequate weed control. At least 0.5 inch of rain after application must occur to ensure adequate weed control. FirstRate is affected by soil pH. High soil pH increases herbicide activity, increases speed of herbicide degradation, but also increases risk of crop injury. Some soybean stunting may occur under poor growing conditions on soils with pH greater than 7.8. FirstRate may increase iron chlorosis symptoms on soils where symptoms have been observed earlier. Use the higher rates on medium to fine textured soils and the lower rates on coarse textured soils. Incorporate uniformly into the top 2 inches for PPI applications. Do not apply to soils with a pH greater than 7.8 as crop injury may result. See label for tank-mix options.

FirstRate at 0.3 oz 80WDG/A applied POST to soybean prior to flowering controls cocklebur, Venice mallow, horseweed (marestail), common ragweed, annual smartweed, sunflower, and velvetleaf and suppresses giant ragweed. Pigweed and lambsquarters are controlled ONLY with soil applications. Apply to broadleaf weeds prior to 10 inches. See label for maximum size of each weed. Use NIS at 0.125 to 0.25% v/v + 28% UAN at 2.5% v/v. Oil additive can be used with or without fertilizer but risk of crop injury increases. See FirstRate under the herbicide residue section for crop rotation restrictions.

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