Corn Herbicide Label and Formulation Changes

March 22, 1999

Dual II Magnum, Bicep II Magnum, and Bicep Lite II Magnum formulations were all available in Illinois during 1998 in somewhat limited quantities. Full conversion to these formulations (replacing Dual II, Bicep II, and Bicep Lite II) will occur this year. "Magnum" formulations contain the resolved isomer of metolachlor; "II" indicates that the formulation contains the corn safener benoxacor. Rate conversion factors are 0.67x for Dual II to Dual II Magnum, 0.90x for Bicep II to Bicep II Magnum, and 0.66x for Bicep Lite II to Bicep Lite II Magnum, where x is the rate of the old formulation.

Frontier X2 contains the active isomer of dimethenamid. Very limited quantities will be in Illinois for the 1999 field season, but full conversion to the resolved isomer formulation should begin to take place during the 2000 field season. Frontier X2 will be used at 55% of the Frontier use rate.

Cyanazine (Bladex, a component of Extrazine II) is still scheduled to be phased out of the market. The original rate structure set for the 1999 season was to be 1 lb a.i. per acre. However, the EPA has approved labels of Bladex and Extrazine II herbicides for the 1999 season only to beused at 3 lb a.i. cyanazine per acre, the same maximum allowable rate of these products that was permitted in 1998. Thus the maximum allowable per-acre application rates of cyanazine-containing products are 3 qt Bladex 4L, 3.3 lb Bladex 90DF, 4 qt Extrazine II 4L, and 4.4 lb Extrazine II 90DF.

Clarity (dicamba) may now be used at 0.5 pt per acre in corn 8 to 36 inches tall with directed application. Do not apply Clarity when soybeans are growing nearby if corn is more than 24 inches tall, soybean are more than 10 inches tall, or soybean have begun to bloom. An additional label change now allows the use of Clarity prior to planting soybean. Use rates prior to soybean planting range from 4 to 16 fl oz per acre. Following a Clarity application up to 8 fl oz, a minimum accumulation of 1 in. of precipitation and a waiting interval of 14 days must occur prior to planting. The waiting interval increases to 28 days (and still requires 1 in. of precipitation) for applications of Clarity greater than 8 fl oz.–MM and AH

Author: Aaron Hager Marshall McGlamery