Rainfall Effects on Desmedipham and Phenmedipham Performance

Abstract
The effect of rainfall on the performance of a tank mixture of desmedipham [ethylm-hydroxycarbanilate carbanilate(ester)] and phenmedipham (methylm-hydroxycarbanilatem-methylcarbanilate) applied postemergence to redroot pigweed (Amaranthus retroflexusL. ♯ AMARE), wild mustard (Sinapsis arvensisL. ♯ SINAR) and sunflower (Helianthus annuusL.) was evaluated in field studies. The occurrence of 1 mm of rain immediately after herbicide application significantly decreased the control of redroot pigweed and wild mustard. A rainfall quantity of 1 mm also reduced injury symptoms on sunflower. Simulating a 12.7-mm rain less than 18 h after desmedipham and phenmedipham application effectively reduced toxicity to redroot pigweed and sunflower. Toxicity to these two species increased at a lesser rate than for wild mustard as the time interval prior to rain was increased. A rain-free period of 6 h was predicted for near-maximum control of wild mustard with these herbicides.