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Corn weed control: Capreno and Halex GT receive aerial labels
Author: Tom Barber, Extension Weed Scientist

Arkansas just received a Section 24(c) Special Local Need label for aerial application of Capreno and Halex GT herbicides in corn. This will hopefully help those producers who have been unable to get into the field with ground rigs due to frequent rainfall. Keep in mind the corn growth restrictions. Any tank mixtures with atrazine need to be applied prior to corn reaching 12 inches of growth, Capreno can be applied from V1 through V5 and Halex GT can be applied to corn up to 30 inches or 8 leaf.  Always read and follow the herbicide label instructions prior to making any application.

ryegrass in cornWeed control applications have been hard to make this year due to the frequent rainfall and wet fields.  Corn fields that received an application of Dual II Magnum or similar product PRE have remained fairly clean and provided much needed time for post applications.  However, where a preemergence herbicide was not applied, fields have grown up fast with several weeds.  Maximum corn yield potential will be lost with extensive weed competition early.  The field to the right will loose a large portion if not all of its yield potential in this corner due to competition from glyphosate resistant ryegrass.  Due to the cool temperatures many of the weeds giving us trouble in the early planted corn are winter annuals that normally emerge in the fall.

Glyphosate resistant ryegrass and horseweed problems in corn have been the bulk of the questions lately.  First of all, big ryegrass is hard to control anyway, but to compound the situation, there are also several populations of ALS resistant ryegrass in the state.  Based on our current data Steadfast Q at 1.5oz/A has been the best option for controlling glyphosate resistant ryegrass in corn.  Keep in mind that Steadfast Q will not work if the population of ryegrass in your field is also ALS resistant.  If the population of ryegrass is resistant to both glyphosate and ALS herbicides, Liberty is probably the only remaining herbicide option if the corn variety planted is Herculex, or tolerant to Liberty.  Two applications 10-14 days apart of Liberty will most likely be needed to provide  marginal control of resistant ryegrass. As we move forward to other crops, make a note of these fields where glyphosate resistant ryegrass has been a problem.  Control of this weed is much more effective with burndown/residual herbicide applications in the fall.

Glyphosate resistant horseweed in many growth stages is also becoming a problem in some corn fields.  Several options to control this in corn, but combinations containing Halex GT plus Atrazine, or combinations with Dicamba would be the best options for controlling newly emerged horseweed or escapes from burndown applications.  Liberty at 29 oz/A is also an option for corn varieties containing the Herculex trait or varieties tolerant to Liberty.

Pigweeds are also emerging in most corn fields, that did not have a PRE down at planting.  Luckily several herbicide combinations with atrazine (Capreno, Halex GT etc.) will control glyphosate resistant pigweed in corn.  The key is timing and like with most weeds, pigweed control is much better when the plants are small.

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