Effects of Rainfall and Adjuvants on Phytotoxicity of Imazethapyr

The experiment was conducted to evaluate the influence of rainfall and four nonionic surfactants on the imazethapyr efficacy in velvetleaf,Abutilon theophrasti. The results showed imazethapyr is a herbicide with excellent rainfastness. The differences of phytotoxicity of imazethapyr under simulated rainfall applied 4 h and 8 h after treatment or no any rainfall are not significant. The addition of nonionic surfactants increased imazethapyr efficacy significantly. Among 4 tested surfactants, AM-100 increased the phytotoxicity of imazethapyr to the greatest extent, the second is PPJ-15, and the last one is SDP. The function of adjuvants to enhance phytotoxicity is more significant with lower dosage of imazethapyr.