Identification of paraquat-resistant solanum nigrum and s. americanum biotypes

Abstract

Sweetpotato (Ipomoea batatas (L.) Lam.) plants are highly susceptible to weed competition during their early field establishment period. For a long time, the contact herbicide paraquat has been widely used within the sweetpotato production system, often as the only herbicide applied to control weeds that emerge within the crop. A low rate of paraquat is applied repeatedly over the crop each season, eliminating seedling weeds at a very young stage, until the crop canopy provides adequate competition. However, the application of paraquat to selectively destroy seedling weeds has inadvertently selected for paraquat-resistant weed biotypes. This study confirms growers' field observations that populations of paraquat-resistant solanaceous weeds are now common, identifying them as Solanum nigrum L. and S. americanum Mill. Paraquat cannot be used selectively when these resistant biotypes are present, as the concentrations required to control the weed species would be lethal to the crop itself.