By Amit Jhala, Extension Weed Management Specialist
Several new herbicides were recently registered for weed control in soybean. These herbicides do not have an active ingredient with a new mode of action; but rather are pre-mixes of existing herbicides that 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 at Marketplace.unl.edu.)
The following soybean herbicides should be available for the 2016 growing season.
Afforia [flumioxazin (40.8%) + thifensulfuron methyl (5%) + tribenuron-methyl (5%)]. This is for burndown and preplant residual control of broadleaf weeds and partial control of annual grasses in soybean. It has two modes of action and rapidly inhibits the growth of susceptible weeds. It can be applied at 2.5 oz/ac a day before planting soybean or 2.5 to 3.75 oz/ac if applied at least 7 days before planting soybean. Crop injury may occur from applications to poorly drained soils under cool, wet conditions. EPA Reg. No. 352-889. Mode of action group: 14, 2.
Authority Elite [sulfentrazone (7.55) + S-metolachlor (68.25)]. It is a soil-applied herbicide for control of broadleaf, grass, and sedge weeds in soybeans. The crop rotation restriction for corn and sorghum is 10 months. A maximum of 38.7 fl oz/ac can be applied per year. EPA Reg. No. 279-3442. BroadAxe XC EPA Reg. No. 279-3442-100. Mode of action group: 14, 15.
Authority Maxx [sulfentrazone (62.12) + clorimuron-ethyl (3.88)]. It can be applied pre-plant or pre-emergence in soybean for broadleaf and partial grass weed control. The application rate is 6 to 9 oz/ac depending on soil texture and organic matter content. EPA Reg. No. 279-9560. Mode of action group: 14, 2.
Fierce [flumioxazin (33.5%) + pyroxasulfone (42.5%)]. Fierce is a new premix for pre-emergence control of broadleaf and grass weeds. The use of residual herbicides can help manage or prevent the development of glyphosate-resistant weed biotypes and reduce early season weed competition. Flumioxazin is a PPO inhibitor and pyroxasulfone is a seedling growth inhibitor. EPA Reg. No. 63588-93-59639. Mode of action group: 14, 15.
Fierce XLT [flumioxazin (24.57%) + pyroxasulfone (31.17%) + chlorimuron (6.67%)]. Fierce XLT in Nebraska can only be used in fields south of US Route 30 and east of US Route 281. This herbicide provides residual control of broadleaf and grass weeds in soybean. It also provides additional burndown activity when used as part of a burndown program. Moisture is necessary to activate this herbicide in soil for residual weed control. Do not apply more than 5.25 oz/ac per growing season. Do not apply additional herbicides containing chlorimuron to fields treated with Fierce XLT. Mode of action group: 14, 15, 2.
Marvel [fluthiacet-methyl (1.2%) + fomesafen (30.08%)]. It is a new premix herbicide from FMC for post-emergence weed control in soybean. It can be applied at 5 to 7.25 fl oz/ac from pre-plant through full flowering stage (prior to R3). It is a contact herbicide and therefore, thorough coverage is essential for optimum weed control. Do not apply more than 7.25 fl oz/ac per application and 9.75 fl oz/ac per year. EPA Reg. No. 279-3455. Mode of action group: 14.
Ransom [flumioxazin (12.92%) + metribuzin (56%)]. It is a selective herbicide for pre-emergence control or suppression of susceptible broadleaf weeds and certain annual grass weeds in soybeans. It also offers control of certain emerged broadleaf weeds when applied as part of a burndown treatment. EPA Reg. No. 66222-260. Mode of action groups: 14, 5.
Rovel [flumioxazin (51%)]. It can be applied to soybeans prior to planting or pre-emergence application must be made within three days of planting soybean. Application after soybeans have begun to crack, or are emerged, will result in severe crop injury. Do NOT apply more than 3 oz/ac per growing season. EPA Reg. No. 59639-99-524. Mode of action group: 14.
Rovel FX [flumioxazin (30%) + chlorimuron (10.3%)]. It is a selective herbicide for pre-emergence control of broadleaf weeds and suppression of certain annual grasses in soybeans. Do NOT apply more than 5 oz/ac during a single growing season. EPA Reg. No. 59639-117-524. Mode of action groups: 2, 14.
Surveil Co-Pack [Surveil V (flumioxazin 51%); surveil™ FR (cloransulam-methyl 84%)]. This is a multi-pack for pre-emergence control of certain weeds in soybeans. Read herbicide label for co-pack load chart. EPA Reg. No. 59639-131-62719. Mode of action groups: 14, 2.
Trivence [chlorimuron ethyl (3.9%) + flumioxazin (12.8%) + metribuzin (44.6%)]. Trivence is a burndown as well as a residual herbicide that may be applied preplant or pre-emergence to soybean. It has three modes of action and rapidly inhibits the growth of susceptible weed species. It can be applied at 6 to 9 oz/ac depending on soil texture and soil pH. EPA Reg. No. 352-887. Mode of action groups: 2, 5, 14.
Warrant Ultra [acetochlor (30.2%) + fomesafen (7.1%)]. It can be applied as a preplant surface, pre-emergence, or post-emergence treatment in soybean. It can provide residual as well as burndown activity. It can be applied only once per growing season and is limited to a maximum of 48 fl oz/ac applied in alternate years in Nebraska. Mode of action groups: 15, 14.
Always refer to herbicide product label for complete details and directions for use.
More information about the efficacy of these herbicides is available in the 2016 Guide for Weed, Disease, and Insect Management in Nebraska (EC130) available online to purchase athttps://marketplace.unl.edu/extension/extpubs/ec130.html. Cost is $15.