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Integrated Pest & Crop Management



AUTHOR

Kevin Bradley
University of Missouri
Division of Plant Sciences
(573) 882-4039
bradleyke@missouri.edu

Applying Preemergence Herbicides to Emerged Corn

Kevin Bradley
University of Missouri
(573) 882-4039
bradleyke@missouri.edu

Published: May 2, 2008

With the wet conditions throughout most of the state, I have already received a few calls about producers sacrificing their preemergence corn herbicide applications in order to try to get as much corn planted as possible. It seems likely that this situation will only get worse and that many growers will not be able to get back on these fields until well after the corn has emerged. Luckily, many of our preemergence corn herbicides have labels that allow them to be applied to emerged corn fields. One notable exception to this is Balance Pro, which cannot be applied to emerged corn or injury will occur. Table 1 provides a list of the preemergence herbicides that can be applied to emerged corn, as well as information about the maximum corn height and/or stage in which these applications should be made.

Table 1: Preemergence herbicides that can be applied to emerged corn
Herbicide
Trade Name
Active Ingredient(s) Maximum Corn Height/Stage for Broadcast Applications Maximum Weed Height/Stage for Broadcast Applications
Aatrex/Others atrazine 12 inches Apply before weeds exceed 1.5 inches in height. When applied with crop oil, apply before weeds reach 4 inches in height.
Bicep II Magnum/Cinch ATZ atrazine + metolachlor 5 inch Apply until weeds reach the 2-leaf stage. Applications made beyond the 2-leaf stage will not provide satisfactory weed control.
Bullet atrazine + alachlor 5 inch Apply until weeds reach the 2-leaf stage. Applications made beyond the 2-leaf stage will not provide satisfactory weed control.
Callisto mesotrione 30 inches or 8-leaf stage Apply to weeds that are less than 5 inches in height.
Camix metolachlor + mesotrione 5 inches Apply before grass emergence but will control some broadleaf weeds less than 3 inches in height.
Degree, Harness, Surpass, TopNotch acetochlor 11 inches Apply before weed emergence. Will not provide postemergence weed control and requires a tank-mix partner.
Cinch, Dual II Magnum metolachlor 40 inches Prior to emergence. Will not provide postemergence weed control and requires a tank-mix partner.
Frontier, Outlook dimethenamid 12 inches Apply before weed emergence. Will not provide postemergence weed control and requires a tank--mix partner.
Degree Xtra, FulTime, Keystone atrazine + acetochlor 11 inches Apply prior to weed seedling emergence or in a tank mixture that controls emerged weeds.
G-Max Lite atrazine + dimethenamid 12 inches Apply before broadleaf weeds are greater than 1.5 inches tall and before grass weeds emerge.
Guardsman dimethenamid 12 inches Apply before weeds are greater than 1.5 inches tall or in a tank mix with products that control emerged weeds.
Guardsman Max atrazine + dimethenamid 12 inches Apply before weeds are greater than 1.5 inches tall or in a tank mix with products that control emerged weeds.
Harness Xtra atrazine + acetochlor 11 inches Apply before grass weeds reach the 2-leaf stage or in a tank mixture with a herbicide that controls emerged weeds.
Hornet flumetsulam + clopyralid 20 inches or V6 stage Apply to specified weeds up to 8 inches in height.
Lasso alachlor before emergence Apply before weed emergence. Will not provide postemergence weed control and requires a tank-mix partner.
Lexar atrazine + metolachlor + mesotrione 12 inches Apply to broadleaf weeds less than 5 inches in height. Will not provide adequate control of most grasses that are emerged at the time of application.
Lumax atrazine + metolachlor + mesotrione 12 inches Apply to broadleaf weeds less than 5 inches in height. Will not provide adequate control of most grasses that are emerged at the time of application.
MicroTech alachlor 5 inches Apply before weed emergence. Will not provide postemergence weed control and requires a tank-mix partner.
Prowl H20 pendimethalin 30 inches or 8-leaf stage Apply before weed emergence. Will not provide postemergence weed control and requires a tank-mix partner.
Python flumetsulam 2 inches or before first leaf is unfurled (spike stage) Apply before weed emergence. Will not provide postemergence weed control and requires a tank-mix partner.
Resolve rimsulfuron 12 inches or exhibiting 6 leaf collars, whichever is more restrictive Apply to grasses 1 to 2 inches in height and broadleaf weeds 1 to 3 inches in height. Will provide postemergence weed control of labeled weeds and some residual control of later-emerging weeds.
SureStart acetochlor + flumetsulam + clopyralid 11 inches Apply before weed emergence up to 1 to 2 inch weeds. If weeds are emerged, apply in combination with another herbicide with contact activity.
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REVISED: April 5, 2012