Corn Production Guide 1

Most herbicides used in corn are labeled for tank-mixing with other herbicides for broadspectrum weed control. Several commercial herbicide mixtures are available for use in corn. Combinations best adapted to North Dakota are given in the chemical weed control tables. Consult the label and discussion of individual herbicides for a complete list of all possible registered combinations.

Herbicide Comments

Eradicane (EPTC plus safener) at 4.75 to 7 pt/A or 16 to 24 lb/A 25G controls grass and certain broadleaf weeds. Eradicane at 6 lb/A gives fair to good quackgrass control. Soil should be dry enough and in good tilth to permit immediate and thorough incorporation. Eradicane is registered as a tank-mixture with atrazine, Bladex and Surpass. Eradicane can be tank-mixed with Surpass to improve performance over a wider range of environmental conditions.

Lasso (alachlor) at 2 to 4 qt 4E/A and Dual (metolachlor) at 1.5 to 3 pt 8E/A are used PPI or PRE to control annual grasses and certain broadleaf weeds such as redroot pigweed, common lambsquarters and common ragweed. Lasso may also be applied POST to corn up to 5 inches tall for PRE control of weeds and reduced competition of labeled weeds. Use the higher rate on clay soils high in organic matter. Incorporation improves weed control with Lasso and Dual. Lasso is registered as a tank-mixture with atrazine, Banvel, Bladex, Roundup Ultra/RT, and Gramoxone Extra. Dual may be surface applied or incorporated in the fall
after October 15 but before ground freezes or applied in the spring. Dual is registered as a tank-mixture with atrazine, Bladex, Banvel or with atrazine plus paraquat or Roundup Ultra/RT. Dual may be applied up to 45 days before planting. Lasso is a restricted use herbicide.

Frontier (dimethenamid) at 13 to 25 fl oz/A is used EPP up to 45 days before planting, PPI, PRE or early POST. Use the higher rate on fine textured soils with greater than 3% OM and the lower rates on coarse textured soils with less than 3% OM. Incorporation may improve weed control in drier conditions. Frontier is registered as a tank-mixture with atrazine, Banvel, Bladex, Roundup Ultra/RT, Marksman, paraquat, Prowl, 2,4-D, and Princep. NDSU field trials have shown Frontier to provide equal or greater weed control than Lasso or Dual. Frontier has shown greater and more consistent weed control in wet climates than Lasso or Dual.

Harness (acetochlor + safener) at 1 to 3 pt/A or Surpass (acetochlor + dichlormid (safener)) at 1 to 3 pt/A or TopNotch (encapsulated acetochlor + dichlormid (safener) at 4 to 7.25 pt/A applied PPI or PRE control annual grasses and certain broadleaf weeds such as pigweed species, common lambsquarters, kochia, nightshade, and common ragweed. Use the higher rate on clay soils high in organic matter. Do not apply Surpass on sands with less than 3% OM, loamy sands with less than 2% OM, or sandy loams with 1% OM, if ground water is within 30 feet of soil surface. Incorporation may improve weed control under dry conditions. Harness Plus is registered as a tank-mixture with atrazine, Eradicane, Prowl, Banvel, Bladex, Roundup Ultra/RT, and Gramoxone Extra. Harness Xtra may be applied up to 45 days before planting.

Prowl (pendimethalin) at 1.8 to 4.8 pt EC or 1.25 to 3.33 lb DG controls annual grasses and certain broadleaf weeds such as redroot pigweed. Prowl must be used only PRE in corn and not PPI. Do not use Prowl on sands or loamy sands or on soils with less than 1.5% organic matter. Prowl can be tankmixed with atrazine, Bladex and Banvel.

Broadstrike + Dual (flumetsulam + metolachlor) at 1.75 to 2.75 pt/A of the premix product or 0.04 to 0.07 lb/A of the Broadstrike component + 1.6 to 2.6 pt 8E/A of the Dual component applied EPP, PPI, or PRE will control some grass and broadleaf weeds. Broadstrike is not packaged individually and is only available as a premix. Broadstrike is very active on small-seeded broadleaf weeds like nightshade, pigweed, kochia, common lambsquarters, mustard, annual smartweed, marshelder, and Venice mallow. Broadstrike may also provide some control of common ragweed and lanceleaf sage.

Hornet (flumetsulam + clopyralid) at 0.2 to 0.3 lb/A of the premix product or 0.05 to 0.07 lb/A of flumetsulam + 0.13 to 0.19 lb/A of the clopyralid component can be applied EPP, PPI, or PRE. Use 0.2 to 0.25 lb/A on coarse textured soils and 0.25 to 0.3 lb/A on medium and fine textured soils. Hornet controls a wide spectrum of broadleaf weeds including nightshade, kochia, pigweed, common lambsquarters, mustard, annual smartweed, wild buckwheat, Venice mallow, marshelder, Russian thistle, horseweed and common ragweed. Hornet has shown excellent activity on large-seeded broadleaf weeds such as common cocklebur and sunflower. Hornet has no activity on grasses, so a grass control herbicide is required either in tank mix or as a separate application.

Atrazine at 1 to 2 lb/A applied PPI or PRE gives good control of annual weeds without corn injury. Fine textured soils with high organic matter require 2 lb/A. Atrazine residues injurious to susceptible crops may remain in soils longer than one growing season. (See herbicide residue section for additional discussion). Atrazine is registered as a tank-mixture with Lasso, bromoxynil (Buctril, others), Sutan+, Bladex, Banvel, Dual, Ramrod. Atrazine is available as a prepackage mix with several herbicides; see table on package mixtures. Atrazine is a restricted use herbicide.

Bladex, Cy-Pro (cyanazine) at 1.3 to 5.3 lb 90DF applied PRE controls annual grass and broadleaf weeds in corn. Use the higher rates on fine textured, high organic matter soils, and the lower rates on coarse textured soils with low organic matter. Do not use on sandy or loamy sand soils, or on soils with less than 1% organic matter. Bladex requires 0.5 inch or more rain for activation, especially on fine textured soils. Bladex is a restricted use herbicide.

Banvel/Clarity (dicamba) at 0.5 to 1 pt/A 4S applied PRE in tank-mixtures with Lasso, atrazine, Accent, Bladex, Dual, or Prowl gives broadspectrum weed control. Banvel/Clarity mixtures are not recommended on coarse-textured sandy soils. Use the lower rate of Banvel on medium soil with 2% OM.

Atrazine at 0.38 to 2 lb ai/A should be applied to corn less than 12 inches tall, broadleaf weeds less than 4 inches tall, or grass weeds less than 1 inch tall. Atrazine gives good wild oat control, partial foxtail (pigeongrass) control, and excellent control of broadleaved weeds (including volunteer sunflower) when used in combination with petroleum oil concentrate or emulsifiable vegetable oil. Atrazine applied with vegetable or petroleum oil at 1 qt/A give similar weed control. Surfactants are less effective with atrazine than any oil additives. Refer to herbicide residue section for carryover precautions. Refer to label for information on application and restrictions based on a RUP status. Atrazine is a restricted use herbicide. See K13 for information on surface applications.

Bladex 90DF, Cy-Pro 90DF (cyanazine) at 1.3 to 5.28 lb 90DF applied as an early POST treatment for grass and broad-leaf weed control (including volunteer sunflower). Emulsifiable vegetable oil at 1 qt/A enhances weed control but may increase the risk of crop injury. Use only the 90DF formulation for POST applications. Bladex or Cy-Pro at 1.3 lb 90DF/A with 1 qt/A of vegetable oil has given good control of small weeds (less than 1.5 inches tall). Occasionally corn leaf burn occurs, but recovery is good. Higher rates will give more consistent weed control but also increase risk of corn injury. Corn should not be treated after the 4th leaf stage, when corn is under stress, or during extended cold, wet conditions. Bladex/Cy-Pro is unlikely to carryover and cause crop injury the next year. Bladex at 1.3 lb 90DF/A rate control emerged weeds in fine-textured soils. Bladex/Cy-Pro are restricted use herbicides.

Basis (rimsulfuron + thifensulfuron) at 0.33 oz 75DF/A can be applied to 4-leaf (2 collar) corn for foxtail, barnyardgrass, redroot pigweed, wild mustard, common lambsquarters, and annual smartweed control. Apply when grasses are 1 to 2 inches tall and broadleaf weeds are 1 to 3 inches tall. A cultivation or sequential application of Accent may be needed to completely eliminate weeds. Basis must be applied with NIS and 28% UAN. Under drought conditions, an oil additive (petroleum or MSO type oil) at 1 to 2% v/v may be substiuted for NIS. Do not use 28% UAN without an NIS. Corn varieties of 88 day maturity or less are more susceptable to injury from Basis than varieties greater than 88 days. Do not apply late.

Basis Gold (nicosulfuron + rimsulfuron + atrazine) at 14 oz 89.46DF/A applied POST to corn up to 12 inches tall controls most all annual grass and broadleaf weeds plus quackgrass. Apply with oil adjuvant at 1 to 2% v/v. NDSU research has shown greater herbicide enhancement from Accent and atrazine applied with MSO type adjuvants than NIS or petroleum oil adjuvants. Apply only to corn hybrids of 88 or more days maturity. Basis Gold at 14 oz 89.46DF/A contains 0.25 oz 75DF/A Accent, 0.75 oz 25DF/A Matrix, and 0.76 lb ai atrazine. NDSU research has shown that good safety exists to most all crops (including small grains and sugarbeet) planted the year following atrazine applied at 0.38 lb ai/A with normal rainfall the year of application. The atrazine in Basis Gold applied at a half rate (7 oz 89.46DF/A) would be equivelent to 0.38 lb ai/A. If a half rate of Basis is used, additional Accent may need to be added to achieve adequate weed control. Applying herbicides at lower than labeled rates makes user liable for product performance and crop injury on crops planted at a shorter interval than directed on the label.

Accent (nicosulfuron) at 0.67 oz 75DF/A can be applied to corn up to 36 inches tall. For corn 20 to 36 inches tall (free standing), Accent should be applied with drop nozzles. Do not apply to field corn taller than 36 inches or with 10 collars, whichever is most restrictive. When banding Accent over the row with a three-nozzle-per-row-system, plug the center nozzle to reduce corn injury from Accent from Accent concentrating in the whorl of the corn plant.

Always add an oil adjuvant at 1% v/v or NIS at 0.25% v/v. Research results at NDSU have indicated that adjuvant enhancement of weed control from Accent was greatest with Scoil (MSO type oil), followed by Sun-It II, petroleum oil, and least with NIS. Use of 28% UAN at 1% v/v with NIS has enhanced weed control compared to Accent plus NIS. Accent may be used POST to control foxtail species, fall panicum, barnyardgrass, field sandbur, woolly cupgrass, wild-proso millet, wild oat, quackgrass, pigweed species, smartweed, wild mustard, jimsonweed, and burcucumber. NDSU results show that Accent provides good control of kochia and fair control of Russian thistle.

Accent can be tank-mixed with atrazine, bromoxynil, (Buctril, others), Buctril + Atrazine, Banvel, Marksman, Scorpion III and many other herbicides. Oil adjuvants should always be used when tank-mixing Accent with atrazine. NDSU research has shown excellent and economic grass and small-seeded broadleaf weed control from Accent tank-mixed with atrazine at 0.38 lb/A with methylated seed oil adjuvants. Accent + atrazine does not adequately control common cocklebur. A sequential application of Banvel or other effective herbicides can be made to control common cocklebur.

Banvel/Clarity (dicamba) at 0.5 to 1 pt/A 4S may be applied alone PRE or early POST to corn from emergence to 8 inches tall. Banvel/Clarity gives better control of Canada thistle, kochia, smartweed, wild buckwheat and volunteer sunflower than 2,4-D with less injury to corn. Banvel alone only at the 0.5 pt/A can be applied if corn is greater than 8 inches tall or at 0.25 to 0.5 pt/A when combined with 2,4-D. Banvel can be applied before corn is 3 feet tall or until 15 days before tassel emergence. Drop nozzles should be used after corn is 8 inches tall to reduce injury if Banvel is applied with 2,4-D and to reduce drift potential. Banvel/Clarity can be mixed with Accent, Bladex and atrazine.

2,4-D amine at 0.5 to 1 pt/A of a 4 lb/gal concentrate applied POST to corn 3 to 8 inches tall will control broadleaf weeds. 2,4-D at 0.5 pt/A will control susceptible weeds like wild mustard and 1 pt/A rate will control tolerant weeds, including volunteer sunflower, but risk of corn injured is greater. Do not apply MCPA to corn, as it is more injurious to corn than 2,4-D. Apply 2,4-D with drop nozzles when corn is over 8 inches tall to reduce corn injury by directing the spray away from the whorl. 2,4-D may cause brittle stalks that may lodge or break. Several brands of 2,4-D are available with some differences on application information; for example, Hi-Dep allows use at spray volumes as low as 1 gpa by ground or 0.5 gpa by air.

Buctril, Bromox, Moxynil, others (bromoxynil) at 1 to 1.5 pt/A or 3.33 to 6.67 A/Gel Pack applied to corn from emergence but before tasselling controls seedling wild buckwheat, volunteer sunflower, and most annual broad-leaf weeds. Some corn leaf burn may occur when high temperatures follow application. Bromoxynil is a contact herbicide so thorough spray coverage is essential for adequate weed control. Bromoxynil can be mixed with atrazine to increase the spectrum of weed control. A com-mercial mixture of bromoxynil plus atrazine is available.

Basagran (bentazon) at 1.5 to 2 pt/A applied POST in corn controls many broadleaf weeds from 2 to 10 inches tall. Basagran will control common cocklebur, giant and common ragweed, smartweed, venice mallow, wild mustard, sunflower and yellow nutsedge. Basagran can control Canada thistle with sequential applications. Corn is tolerant to Basagran at all stages. Liquid fertilizer can be used with Basagran in place of oil concentrate for improved control of several weeds. Basagran can be applied in corn when drift of Banvel or 2,4-D may injure sensitive crops.

Sencor (metribuzin) at 1.6 to 2 oz 75DF/A or 2.4 to 3 fl oz 4F applied POST with another herbicide labeled for tankmix use with Sencor controls many broadleaf weeds. Sencor can be tankmixed with atrazine, Banvel, Basagran, bromoxynil (Buctril, others), Clarity, Marksman, and 2,4-D. Use drift reducing methods when tankmixing with Banvel, Clarity, Marksman, or 2,4-D ester. Consult label for adjuvant use with the different tankmix options. Do not use oil additives with any Sencor tankmix. Corn can be grazed, or harvested for silage or grain 60 days after treatment.

Permit (halosulfuron) at 2/3 to 1 1/3 oz 75DF/A applied POST in corn controls nutsedge and some broadleaf weeds in corn. Permit provides excellent control of sunflower, common and giant ragweed, and common cocklebur. Permit must be tank-mixed with 2,4-D or Banvel/Clarity for common lambsquarters and pigweed control. Always add NIS or oil additive. Addition of 28% UAN may enhance control of larger pigweed. Unlike many sulfonylurea herbicides, high soil pH does not contribute to persistance in the soil. Degradation of Permit increases as soil pH increases. However, Permit can have a residue in the soil the year following application. Refer to the label or "Herbicide Residue" section of this guide for more information on crop rotation restrictions.

Scorpion III (flumetsulam + clopyralid + 2,4-D acid) at 0.25 lb 84.3DF/A of the premix product contains 0.023 of flumetsulam + 0.063 lb of clopyralid + 0.125 lb of 2,4-D acid. Apply POST to corn up to 8 inches tall (measured to the top of the whorl). Later applications may be made if the spray is directed below the whorl using drop nozzles. Do not apply less than 85 days before harvest. Do not apply by air. Always add NIS at 0.25% v/v. Under adverse environmental conditions, add NIS at 0.25% v/v AND 28% UAN at 2.5% v/v. Apply to weeds in the 2- to 4-leaf stage. Scorpion III provides excellent control of a wide range of broadleaf weeds including sunflower, kochia, Russian thistle, pigweed spp., lambsquarters, common and giant ragweed, mustard spp., marshelder, and nightshade spp.

Emergency control of broadleaf and grass weeds in corn can be obtained with Evik or Gramoxone Extra applied POST directed. Evik at 2 to 2.5 lb/A or Gramoxone Extra at 0.25 lb/A should be applied as a directed spray to the weeds. A NIS must be used with both herbicides. These herbicides applied over the top of corn will cause severe injury and contact with the leaves will cause burning. Do not apply Evik before corn is 12 inches high or paraquat before corn is 10 inches high. Weeds should be less than 4 inches tall.

Herbicide Tolerant Corn

IMI-Corn

Lightning (imazethapyr + imazapyr) at 1.28 oz 70WDG/A (0.64 oz imazethapyr + 0.15 oz imazaquin) controls most annual grass and broadleaf weeds plus season-long suppression of perennial weeds including quack-grass and Canada thistle. Apply Lightning EPOST or POST only to IMI-corn varieties and to weeds 2 to 4 inches tall. Apply with adjuvant and liquid fertilizer. Refer to label for weeds controlled, adjuvants, application information and timing, tankmix options, insecticide interaction, and crop rotation restrictions.

Liberty Tolerant Corn

Liberty (glufosinate) at 16 to 28 fl oz/A (0.2 to 0.365 lb/A) control most annual grass and broadleaf weeds plus suppression of some perennial weeds. Apply Liberty EPOST or POST to Liberty tolerant corn up to 24 inches tall or with 7 collars (V7). Liberty is a nonselective, nonresidual, contact type herbicide with limited translocation. Liberty should be applied to small weeds because of limited translocation. Liberty is nonresidual which may require multiple applications or applying with a residual herbicide to control multiple weed flushes. Nonresidual nature of Liberty will allow any crop to be planted the following year. Liberty can be applied with spray grade AMS fertilizer. Refer to label for weeds controlled, application information and timing, tankmix options, restriction. application information, and other restrictions.

Sethoxydim Resistant (SR) Corn

Poast (sethoxydim) at 0.5 to 1.5 pt/A applied only to Poast (Sethoxydim) Resistant (SR) Corn varieties will control annual including barnyardgrass, field sandbur, foxtails, wild proso millet, and suppress quackgrass. Apply POST with oil additive at 1 qt/A to actively growing grasses 2 to 6 inches tall. Drift and off-site movement may cause injury or death to grass weeds and crops.

Restrictions on Feeding and Grazing of Corn Treated with Herbicides

Bladex, Dual, Eradicane, Lasso, Lorox, Prowl, Ramrod, Scorpion III, Sutan +: No restrictions.

Accent, Basis, Buctril, Permit: Do not feed or graze for 30 days after application.

Banvel, Clarity: Do not graze or harvest for feed prior to ensilage (milk) stage of crop.

Rotation Restrictions for Corn


Herbicide	Months after Application

Ally	22a
Amber	22
Assert	NCS
Broadstrike + Treflan	8
Buckle	16
Curtail	1
Exceed	f
Far-Go	NCS
Finesse	f
Lexone	4^p
Lightning	8.5
Peak	1
Prowl	0^q
Pursuit	8.5
Sencor	4^p
Sonalan	NCS
Tordon (<1.5 oz)	SCS^r
Treflan/Trifluralin	NCS^s

NCS = Next cropping season after herbicide application. SCS = Second cropping season after herbicide application.
^a Do not use on soil with pH greater than 7.9. Requires 22 months and 22 inches of precipitation west of Hwy 1 or 34 months and 34 inches of precipitation east of Hwy 1. ^fDo not plant until field bioassay indicates it is safe. ^hBuckle is labeled as a fall treatment in durum wheat and spring PPI application for durum and HRSW (some varieties excluded). ^pMust add 2 months if soil pH is 7.5 or above. Wheat and barley can be planted 4 months after application following lentils or soybeans. ^qCorn can be planted only if Prowl is applied PRE. DO NOT APPLY PPI. ^rDo not plant corn or sorghum until soil samples analyzed for Tordon residue indicates no detectable levels present. Restriction is based on non-legal residue that may be found in corn and sorghum and not on crop safety. ^sOats, sorghum, and annual or perennial grass crops may be planted at least 12 months after application in areas that received 20 inches or more of precipitation during the growing season.

Corn Production Guide (continued)

Herbicide Tolerant Corn

IMI-Corn

Liberty Tolerant Corn

Sethoxydim Resistant (SR) Corn

Chemical Names, Formulations and Manufactuer

Herbicide Premixes

Prepackaged Mixtures Available for Corn

Herbicide Comments

Herbicide Tolerant Corn

IMI-Corn

Liberty Tolerant Corn

Sethoxydim Resistant (SR) Corn

Restrictions on Feeding and Grazing of Corn Treated with Herbicides

Rotation Restrictions for Corn