When developing an integrated weed management (IWM) plan, farmers should consider what happens when things don’t go according to plan. A wet spring or fall can impact a farmer’s ability to use tillage or apply a herbicide prior to planting. However, there are several herbicide products that can be applied PRE and POST in corn to overcome this challenge. Although there is flexibility, applying these herbicides as soon as possible after planting should be considered to decrease the risk of poor herbicide performance. When a weed control tactic is delayed, weeds will continue to grow, and application rates may need to be increased to provide satisfactory control. Rotational crop interval restrictions must also be kept in mind with later than normal applications. As with all pesticides, read and understand the label for each product prior to application.
A burndown herbicide program can help reduce weeds prior to planting. DiFlexx® herbicide, DiFlexx® DUO herbicide, Roundup PowerMAX® herbicide, or XtendiMax® herbicide with VaporGrip® Technology (a restricted use herbicide) are products that can be used or included in a tank mix prior to planting. Consult each product label to determine use requirements and possible tank mix options. Each field should be scouted to determine weed species and size prior to selecting the best product. While not optimal, late burndown in corn is not catastrophic. Because there is activity of some residual corn herbicides (e.g. atrazine) on weeds that have emerged, XtendiMax herbicide with VaporGrip Technology and DiFlexx herbicide can be used for control of emerged weeds around the time of planting and after the crop has emerged.
If you have selected a corn product with Roundup Ready® 2 Technology, Roundup PowerMAX® herbicide can be used PRE through the V8 stage or until corn plant height reaches 30 inches, whichever comes first. Additional burndown choices for any field corn seed product include XtendiMax® herbicide with VaporGrip® Technology (a restricted use herbicide), DiFlexx® herbicide, Diflexx® DUO herbicide, and Laudis® herbicide (applied up to V8 stage) which can be applied to emerged corn. If weeds are 3 inches or less in height, Capreno® herbicide can be used as burndown and provide early season residual control. It is recommended that the product be applied as soon as possible after planting to control emerged weeds. Using a product or tank mixing with a product that provides early residual control can also be beneficial. Products like Capreno herbicide, and Harness® MAX herbicide can help extend residual activity when tank mixed with your other herbicide options. Capreno herbicide can be used for foliar and residual control of grass and broadleaf weeds, while Harness MAX can be used for foliar control of broadleaf weeds and residual control of both grass and broadleaf weeds. Laudis® herbicide is another option that can add foliar control and a short-term residual on grass and broadleaf weeds.
Including atrazine can help provide control of many broadleaf weeds and some grass species. Balance® Flexx herbicide can help provide control of both grass and broadleaf weeds. These herbicides in combination with a premix acetochlor brand (Degree Xtra® herbicide, Harness® Xtra herbicide, or Harness® Xtra 5.6 herbicide) can provide good control with multiple effective sites of action for weed control. Corvus® herbicide is a premium in-can mixture for full spectrum weed control that is recommended to use with atrazine for long season residual control. TripleFlex® herbicide and Harness® MAX herbicide provide residual control of grass and broadleaf weeds and can be used outside of areas where there are atrazine or isoxaflutole (active ingredient in Corvus herbicide and Balance Flexx herbicide) restrictions. Check labels and consult locally with experts for a local tailored solution.
For control of emerged weeds, Roundup PowerMAX® herbicide can be used PRE through the V8 stage or until corn plant height reaches 30 inches, whichever comes first, on field corn products with Roundup Ready® 2 Technology. Laudis® herbicide can be tank mixed with glyphosate products for enhanced control of broadleaf weeds and some grasses and glyphosate-tolerant weeds. Additionally, when glyphosate-tolerant weeds are a concern, DiFlexx® herbicide, which is a dicamba product, or DiFlexx® DUO herbicide, which contains dicamba and tembotrione, can be broadcast applied to corn up to V7 or 36 inches crop height, whichever comes first. Both of these products include a safener.
Harness® MAX herbicide includes acetochlor and mesotrione and Harness® Xtra herbicide includes acetochlor and atrazine. Both herbicides can be applied to corn that is up to 11 inches tall. TripleFLEX® II herbicide includes acetochlor, flumetsulam, and clopyralid and can be applied to corn that is 11 inches tall. Balance® Flexx herbicide can be applied from spike to V2 growth stage. Corvus® herbicide contains isoxaflutole and thiencarbazone-methyl and can be applied to corn from spiking to V2 growth stage. A tank mix with atrazine for both Balance Flexx herbicide and Corvus herbicide is recommended for additional control of broadleaf weeds. Capreno® herbicide contains both tembotrione and thiencarbazone and provides control of broadleaf and grass weeds and can be applied to corn through the V7 growth stage.