Pendimethalin Residues from Weed Management in Dry Bean Can Cause Injury in Autumn Seeded Winter Wheat

Abstract

There is little information on effect of pendimethalin residues in the soil used for weed management in dry bean, on winter wheat seeded 3 to 4 months after application in Ontario. A total of four field experiments were conducted over a four-year period (2008-2011) in Ontario to evaluate the effect of pendimethalin residues on winter wheat injury and yield grown in rotation with dry bean. Pendimethalin, applied PPI in dry bean, at 1080 and 2160 g ai ha -1 caused 1% to 3% injury and 4% to 9% winter wheat injury evaluated 1 and 4 weeks after emergence (WAE) in the fall and on approximately the first of May, June and July of the following year. Pendimethalin applied PPI in the spring at 1X or 2X manufacturer’s recommended rate (1080 or 2160 g ai ha -1 ) in dry bean caused no adverse effect on the winter wheat height evaluated in July of the following year and no adverse effect on maturity at harvest. Pendimethalin applied PPI at 1080 g ai ha -1 in dry bean in the spring caused no adverse effect on winter wheat yield, but pendimethalin applied at 2160 g ai ha -1 rate caused a 4% reduction in yield of winter wheat. Based on this study, pendimethalin applied PPI at 2160 g ai ha -1 has potential to cause injury and yield reduction in winter wheat grown in rotation with dry bean under Ontario environmental conditions.