Preliminary Studies On Effect Of Herbicides On Rhizoctonia Solani Of Cotton

In recently years, herbicides were applied widely. Concerns have been raised about effect on non-target after application with herbicides. Cotton is one of important economic crops in our country. With widely used of chemical weeding in cotton, the disease of cotton arosed by Rhizoctonia solani Kuhn was more and more aggravated. The purpose of this paper is to study effect of herbicides on Rhizoctonia solani of cotton. In this study, 12 herbicides (alachlor, acetochlor, metolachlor, pendimethalin,dibutralin,trifluralin,oxadiazon,prometryne,sethoxydim,haloxyfop-R-methyl,fluazifop-p-butyl,quizalofop-p-ethyl) were determined on R.solani in vitro such as the growth rate, dry weight of the mycelium, pathogenicity. In greenhouse, the pathogenicity of scleraotium and cotton after treatment with 12 herbicides was studied; At last, effect mechanism of herbicides on R.solani of cotton was studied. The results could be summaried as follows:1. The studies of 12 herbicides on R.solani in vitro showed that the toxicity of 12 herbicides to R.solani was different. Toxicity of Fluazifop-p-butyl, Quizalofop-p-ethyl and Haloxyfop-R-methyl were more than other herbicides,and EC50 of Quizalofop-p-ethyl was 17.72 mg. L^-1 .2. The mycelial dry weight was inhibited by all herbicides and with the higher dosage the inhibity was higher.The inhibity of Fluazifop-p-butyl, Quizalofop-p-ethyl and Haloxyfop-R-methyl were higher than other herbicides,and theirs inhibite rate were all up 85% at the dosage of 50 mg.L^-1 while the inhibite rate of trifluralin, Oxadiazon and sethoxydim were all below 80% at the dosage of 200mg.L^-1.