Use of AC 263,222 for Sicklepod (Cassia obtusifolia) Control in Soybean (Glycine max)

Abstract

Field experiments were established in 1989 and 1990 to determine the effects of application rate and timing on sicklepod control and soybean tolerance to POST applications of AC 263,222 and chlorimuron. When applied to 3-, 6-, or 10-leaf sicklepod, 35 g ai ha^-1or more AC 263,222 controlled more than 85% of sicklepod early in the season, and season-long when applied to 3- or 6-leaf sicklepod. At all timings, 70 g ha^-1or more AC 263,222 resulted in better control than a PRE application of 420 g ai ha^-1metribuzin followed by 9 g ai ha^-1chlorimuron applied POST. At 35 g ha^-1or more AC 263,222, application timing did not affect sicklepod control. However, control was reduced with 18 g ha^-1when applications were delayed from 3- or 6-leaf to 10-leaf sicklepod. At the 10-leaf sicklepod growth stage, a PRE application of imazaquin increased both sicklepod control and soybean yield with 35 g ha^-1AC 263,222 as compared with AC 263,222 applied alone. Soybean injury and height reductions with AC 263,222 at 35 g ha^-1and above were greater than with chlorimuron; however, increased soybean injury or height reduction was not reflected in pod numbers or yield.