By Amit Jhala, Extension Weed Management Specialist
Several new herbicides have been registered for weed control in corn. These herbicides do not have an active ingredient with a new mode of action, but rather are pre-mixtures of existing herbicides. They can provide excellent weed control if applied according to label directions. A season-long weed management plan should include herbicides with multiple modes of action.
(See Classification of Herbicides by Mode and Site of Action and Chemical Family, excerpted from the 2016 Guide for Weed, Disease and Insect Management in Nebraska, available atMarketplace.unl.edu.)
In the following list of new corn herbicides for 2016, application timing is indicated as pre-plant, pre-emergence (after planting but prior to crop emergence), or post-emergence (after crop emergence).
• Acuron [atrazine (10.93) + mesotrione (2.6%) + S-metochlor (23.4%) + bicyclopyrone (0.65%)]. Acuron may be used pre-emergence or post-emergence (up to 12 inches tall) in field corn, seed corn, and silage corn. It can be used in sweet corn and yellow popcorn, but only pre-emergence. Acuron contains the safener benoxacor. If organic matter content of the field is less than 3%, apply Acuron at 2.5 qt/ac, and if more than or equal to 3%, apply at 3 qt/ac. Do not exceed 3 qt/ac of Acuron per year. EPA Reg. No. 100-1466. Modes of action: 5, 15, 27.
• Anthem MAXX [pyroxasulfone (45.22%) + fluthiacet (1.38%)]. Anthem MAXX is a new formulation of Anthem, a premix for pre-emergence or early post-emergence control of annual grasses and some small-seeded broadleaf weeds in corn and soybean. EPA Reg. No.279-3468. Modes of action: 14, 15.
• Armezon PRO [topramezone (1.12% + dimethenamid-P (56.25%)]. It is an emulsifible concentrate (EC) that provides systemic post-emergence control of emerged broadleaf and grass weeds followed by residual control in all corn types. Application rates depend on soil texture and organic matter content. It may be applied from corn emergence to V8 stage or 30 inches tall field corn and popcorn. For applications when corn is more than 12 inches tall but less than 30 inches tall, direct applications beneath the crop canopy using drop nozzles and appropriate nozzle spacing for best performance. EPA Reg. No. 7969-372. Modes of action: 15, 27.
• DiFlexx [dicamba (56.6%)]. DiFlexx includes exclusive CSI™ Safener technology which enables corn plants to better withstand herbicidal activity and provides better crop safety. DiFlexx may be used for pre-emergence or post-emergence selective control of broadleaf weeds in corn and fallow croplands. The application rates of DiFlexx vary with weed type and growth stage. Do not apply more than 16 fl oz/ac per application and a total of 24 fl oz/ac per year. Apply maximum of two applications per growing season, separated by two weeks or more. EPA Reg. No. 264-1173. Mode of action: 4.
• DiFlexx DUO [dicamba (19.73%) + tembotrione (2.83%)]. DiFlexx DUO is a selective pre-emergence and post-emergence herbicide for control of annual broadleaf weeds; control and/or suppression of many biennial/perennial broadleaf weeds and control of annual grasses found in corn (field corn, seed corn, popcorn, and corn grown for silage) and for post-harvest burndown weed control. Weed control ceases within hours after DiFlexx DUO is applied. Symptoms on susceptible weed species include epinastic-like symptoms on stems and leaves with tissues turning yellow and bleached in color and soon becoming necrotic. Plant death generally occurs within 7 to 14 days after application. EPA Reg. No. 264-1184. Modes of action: 4, 27.
• Fierce [flumioxazin (33.5%) + pyroxasulfone (42.5%)]. Fierce is a new premix for pre-emergence control of broadleaf and grass weeds. It is labeled for use in soybeans and no-till and minimum till corn. It should be applied 10 days before planting corn. The use of residual herbicides, such as Fierce, reduces early season weed competition. Modes of action: flumioxazin is a PPO inhibitor (MOA Group14) and pyroxasulfone is a seedling growth inhibitor (MOA Group 15). EPA Reg. No. 63588-93-59639. Modes of action: 14, 15.
• Resicore [acetochlor (31%) + mesotrione (3.3%) + clopyralid (2.7%)]. Resicore™ herbicide may be used preplant, pre-emergence, or post-emergence in field corn, field seed corn, and field silage corn. For yellow popcorn, Resicore must be applied prior to crop emergence (i.e., preplant or pre-emergence) or severe crop injury may occur. Resicore is a combination of the herbicides acetochlor (MOA Group 15), mesotrione (MOA Group 27), and clopyralid (MOA Group 4), plus the crop safener furilazole. This combination of three herbicide modes of action controls many grass and broadleaf weeds by interfering with normal germination, growth, and seedling development. When applied after weed emergence, Resicore will provide control of many broadleaf weed species, but will not provide consistent control of emerged grass weeds. Modes of action: 15, 27, 4.
• Solstice [fluthiacet methyl (2.2%) + mesotrione (38.52%)]. It contains two active ingredients possessing both contact and systemic activity that can be applied post-emergence for selective control of broadleaf weeds in field corn, seed corn, yellow popcorn, and sweet corn. It can be applied up to V8 corn growth stage or until corn is 30 inches tall. Application rate is 2.5 to 3.15 fl oz/ac. If atrazine is mixed with Solstice, do not apply to corn that is more than 12 inches tall. EPA Reg No. 279-3461. Modes of action: 14, 27.
For more information about weed control efficacy and crop safety of these herbicides, refer to the 2016 Guide for Weed, Disease, and Insect Management in Nebraska (EC130) available for sale online at https://marketplace.unl.edu/extension/extpubs/ec130.html
Always refer to herbicide product label for complete details and directions for use.