Effect of flumetsulam plus clopyralid soil residues on potatoes (Solanum tuberosum L.), lima beans (Phaseolus limensis, L.) and snap beans (Phaseolus vulgaris L.) grown in rotation

Field experiments to characterize the sensitivity of potatoes, lima beans, and snap beans to soil residues of flumetsulam plus clopyralid applied to maize the previous year were conducted in 1999/2000 at three sites in the Midwestern USA. Flumetsulam plus clopyralid was applied post-emergence to maize in 1999 at 144, 288, and 576 g ai/ha. Selected vegetable crops were planted in 2000. Soil residues of flumetsulam plus clopyralid resulted in greater injury to potatoes planted the following year than to lima beans or snap beans. Severe potato injury was observed at Fremont, OH, ranging from 11% to 21% at 7 days after emergence (DAE) showing a dose response. Potato injury was greatest at the site with low soil pH and least precipitation between herbicide application and vegetable crop planting. Lima beans tolerated flumetsulam plus clopyralid soil residues and were not injured at any of the test sites. Snap beans were injured slightly at one of the four test sites at normal use doses. These results suggest that lima and snap beans, but not potatoes, can tolerate soil residues of flumetsulam and clopyralid 365 days after application to maize.