Soil and environmental factors affecting the efficacy of pyroxasulfone for weed control.

Pyroxasulfone inhibits very-long-chain fatty acid elongase in susceptible weeds and facilitates preemergence weed control. Pyroxasulfone showed 98% control of Echinochloa crus-galli (ECHCG) for up to 63 days at a use rate lower than that of chloroacetamide herbicides. ED90 of pyroxasulfone against ECHCG in soil with high organic matter (OM) content did not differ significantly from that in lower OM soils. The low water solubility and the low vapor pressure of pyroxasulfone resulted in limited horizontal diffusion on the soil surface and low risk of volatilization, respectively. The herbicidal efficacy of pyroxasulfone was affected by clod size and improved with smooth soil surface preparation.