The effect of cotton selective soil applied herbicides on severity of damping off(Rhizoctonia solani)

This investigation was conducted to evaluate the effect of herbicides trifluralin, ethalfluralin and alachlor on expression of damping off caused by Rhizoctonia solani on three varieties of cotton in sterile or non-sterile soil. The experiments were carried out in 2011 at greenhouse of Department of Weed Research, Iranian Research Institute of Plant Protection. The severity of the disease was compared with control including not using herbicide/with pathogen. The results in non-sterile soil indicated that herbicides had no significant effect on the severity of disease occurrence on variety named Avangard. Ethalfluralin significant decreased the disease incidence on Sepid variety. But on variety Varamin, just alachlor significantly enhanced the expresion of the disease. The results in sterile soil, showed no significant difference between herbicide treatments with control on varieties named Varamin and Sepid, but on variety Avangard using trifluralin significantly enhanced the occurrence of disease. These results indicated that the influence of herbicides on severity of damping off caused by R. solani depends on kind of herbicide used in soil, cotton variety and soil micro-organisms.