Preemergence corn herbicides applied postemergence

Many producers, especially those using no-till, also have been concerned that weed size may exceed the range of most preemergence herbicides by the time they are applied this year. Many of these products contain 1.0-1.5 lb of atrazine and have burndown properties. Control can be expected of 4-inch broadleaf weeds with a 1.5 lb rate and 2- to 3-inch broadleaf weeds with 1.0 lb atrazine.

The postemergence activity of atrazine can be increased by including an oil additive. Do not apply preemergence herbicdes with liquid nitrogen solutions to emerged corn.Most atrazine containing herbicides prohibit applications in liquid nitrogen after corn emergence because of unacceptable crop injury. If you have planted Roundup Ready corn you can add glyphosate to the mixture. Keep in mind glyphosate activity may suffer when mixed with other herbicides so the 1 qt rate should be used.

Another option with Roundup Ready corn would be to use Field Master or Expert. Both contain a pre grass herbicide, atrazine and glyphosate as a premix. Do not use these products when using 10-34-0 or a flowable fertilizer in the tank). Also if you are considering adding 2,4-D to the mixture, it is best if the entire field is in at least the spike stage to avoid injury to the corn.

Additionally, please note that Balance is not registered post- emergence. If used postemergence, injury may occur. DO NOT use Balance on light sandy soils with low organic matter.

Also, crop oil (COC) can be added with some mixtures to enhance weed control, but be sure to check the label as it may cause crop injury.

Alex Martin
Extension Weed Specialist

Table 1. Preemergence herbicides that can be applied postemergence in corn. Treatment Crop Stage Weed Stage Aatrex/Atrazine 0-12” 1.5”G Bicep II Magnum/ Cinch ATZ 0-5” 2-leaf G&B Bicep II Lite Magnum/ Cinch ATZ lite 0-5” 2-leaf G&B Bicep II Magnum FC 0-5” 2-leaf G&B Bullet 0-5” 2-leaf G&B Callisto# 0-30" 0-5B Degree 0-11” unemerged Degree Xtra 0-11” 2-leaf G&B Dual Magnum 0-5” unemerged Dual II Magnum/ Cinch 0-5” unemerged Dual + Aatrex 0-5” 2-leaf G&B Expert#, ##, ### 0-12” weeds < 6” FieldMaster*, ### 0-11” weeds < 6” G-MAX Lite 0-12” 1.5G&B Guardsman Max 0-12” 1.5"G&B Harness/Confidence 0-11” unemerged Harness/Xtra/Confidence Xtra 0-11” 2-leaf G&B Hornet WDG 0-20” 2-6"G&B Keystone 0-11” unemerged Keystone LA 0-11” unemerged Lasso 0-5” 2-leafB Lasso + Atrazine 0-5” 2-leaf G&B Lasso+ Banvel 0-3” 2-leafB Lead Off 0-8” 1.5"G&B Lightning (IMI corn) corn < 8-leaf weeds < 3"G&B Lumax/Lexar# 0-5" 0-3"B Marksman 0-8" 0-4"B Me-Too-Lachlor II 0-40" 2-leafB Outlook 0-12" unemerged Pendimax/Prowl 0-24" 1"G Prowl H20 0-30" 1"G Prowls + Atrazine up to 2-leaf up to 2-leaf Stalwart C 0-40" 2-leafG Stalwart Xtra 0-5" 2-leaf G&B Surpass 0-11 unemerged Topnotch 0-11 unemerged Trizmet II 0-5 2-leafG&B # Severe injury may occur if Callisto is applied postemergence to corn crops that have been treated with Counter or Lorsban. Do not tank mix with any organophosphate or carbamate insecticide. Do not cultivate within seven days of application. ## Do not tank mix this product with any other herbicide when applied postemergence. ### Do not mix this product with complex fertilizer mixtures such as 10-34-0 or flowables. Use only water or liquid nitrogen carrier. *Apply this product to Roundup Ready corn only GGrass BBroadleaf

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