New Corn Herbicides for 1999

March 22, 1999

Several new corn herbicides will be available for the 1999 growing season. Some are new active ingredients not previously available, while others are premixes of older products. Note that this article is a short summary of new additions to the market, not an exhaustive description of each product. Be sure to read and follow label directions for any pesticide.

Aim 40WDG (carfentrazone) is a postemergence herbicide manufactured and marketed by FMC. It belongs to the same chemical and mode-of-action families as Authority (sulfentrazone), which is used preemergence in soybean. Aim may be applied at 0.33 ounce per acre until corn reaches the 8-collar leaf stage. Several other herbicides may be tank-mixed with Aim to broaden the weed control spectrum; however, the label indicates that Aim should not be tank-mixed with emulsified concentrate (EC) formulations, as this increases the probability of corn injury. Applications should include a nonionic surfactant (NIS) at 0.25% v/v, but not crop oil concentrate (COC) unless under very dry soil moisture conditions. Labeled weeds include 1- to 4-inch nightshade, lambsquarters, and redroot pigweed; 2- to 3-leaf pitted and ivyleaf morningglory; and up to 36-inch velvetleaf. With the limited weed control spectrum, it is likely that Aim will be utilized primarily as a tank-mix component with other postemergence corn herbicides. Corn injury, primarily leaf chlorosis and necrosis, has been observed with this herbicide in research plots.

Axiom 68DF (flufenacet + metribuzin) received a label during the 1998 season, but too late to facilitate much utilization. Axiom may be applied preplant (up to 45 days prior to planting in conservation tillage systems), preplant incorporated, or preemergence for control of certain annual grass and broadleaf weed species. Rates range from 13 to 23 ounces per acre depending on soil type, organic matter, and tillage. Axiom may be tank-mixed with several other soil-applied herbicides and may also be used in soybean. However, application rates range from 7 to 13 ounces per acre for soybean production systems.

Balance 75WDG (isoxaflutole) represents a new herbicide mode of action for use in corn. Balance inhibits an enzyme site in a pigment-synthesis pathway, which results in affected plants appearing white in color. This symptomology is similar to that of Command. Balance may be applied preplant (up to 14 days prior to planting conventional corn hybrids or 30 days prior to planting Roundup Ready or Liberty Link hybrids where a sequential postemergence application of glyphosate or glufosinate is planned), preplant incorporated, or preemergence for control of certain annual grass and broadleaf weed species. Application rates range from 1 to 3 ounces per acre and are determined by soil type, tillage system, and application timing. Balance should not be applied on sand, sandy loam, or loamy sand soils if the water table is less than 25 feet below ground surface. Plant corn at least 1.5 inches deep, and be certain the seed is completely covered. Do not apply Balance after corn emergence, or severe corn injury may result. Balance provides good control of several broadleaf and grass species (including woolly cupgrass) but is weak on cocklebur, morningglory, giant ragweed, yellow foxtail, crabgrass, and sandbur. Tank-mixing Balance with other herbicides can broaden the grass and broadleaf control spectrum.

Distinct 70WG (diflufenzopyr + dicamba) is a postemergence herbicide from BASF for control of annual broadleaf weed species and control or suppression of certain perennial broadleaf species. Although this herbicide does not actually control grass weeds, suppression of growth (grass 3 inches or less in height) following application can often be observed on species such as foxtails and fall panicum. The manufacturer has coined the term "herbistatic" to describe the grass activity of Distinct. Distinct may be applied at 6 ounces per acre to corn between 4 and 10 inches in height, and at 4 ounces to corn between 10 and 24 inches. Applications of Distinct should include an NIS (0.25% v/v) and ammonium nitrogen source (1.25% v/v UAN or 17 pounds AMS per 100 gallons). Distinct is not recommended for use in tank mixes with plant growth regulator herbicides such as those products that contain dicamba, 2,4-D, or clopyralid.

Epic 58WDG (flufenacet + isoxaflutole) contains one active ingredient of Axiom premixed with the active ingredient of Balance. This herbicide may be applied preplant (up to 14 days prior to planting), preplant incorporated, or preemergence at 8 to 20 ounces per acre, depending on soil type and application timing, for control of annual grass and broadleaf weed species. Do not apply Epic after corn emergence, or severe corn injury may result. Because Epic contains the active ingredient of Balance, these products have many similar use restrictions.

Liberty ATZ 4.3L (glufosinate + atrazine) is a premix of Liberty and atrazine for postemergence applications to Liberty Link or GR corn hybrids only. Application rates range from 32 to 40 fluid ounces per acre. Always include AMS (3 pounds per acre) with Liberty ATZ, and make applications to corn up to 12 inches in height. Do not include any NIS or COC. Some limited soil-residual activity from the atrazine component may be expected following application.

NorthStar 47.4WDG (primisulfuron + dicamba) is a premix of Beacon and a dry formulation of Banvel marketed by Novartis. This product will replace herbicides containing prosulfuron (Exceed, Spirit) in areas of Illinois where prosulfuron carryover has occurred. NorthStar may be applied broadcast at 5 ounces per acre when corn is between 4 and 20 inches in height (V2—V6). Directed applications may be made to corn up to 36 inches in height. Although primarily for broadleaf weed control, NorthStar may provide some control or suppression of grass weeds as well. Applications should include NIS or COC (until corn reaches 12 inches in height), and an ammonium nitrogen fertilizer (UAN or AMS) may also be included. The NorthStar label contains several use precautions for applications to corn previously treated with certain insecticides.

LeadOff 5L (dimethenamid + atrazine) is marketed by DuPont. This formulation is identical to Guardsman.

Bicep Magnum TR 4.59L (metolachlor + atrazine + flumetsulam) has flumetsulam (Python) added to Bicep Magnum for improved control of triazine-resistant weed biotypes.–AH and MM

Author: Aaron Hager Marshall McGlamery