A laboratory experiment was conducted in the Department of Plant Pathology, College of Agriculture, Kerala Agricultural University, Vellayani, Thiruvananthapuram to study the effect of the new generation sulfonyl urea herbicide, pyrazosulfuron ethyl on the major soil born rice pathogen Rhizoctonia solani
. Six different concentrations of pyrazosulfuron ethyl (20, 30, 40, 50, 60 and 70 ppm) along with control (without herbicide) were evaluated following poisoned food technique. Results revealed that pyrazosulfuron ethyl at different concentrations except 20 ppm tested significantly inhibited the radial growth of pathogen at initial stages of inoculation i.e., one day after inoculation (1 DAI). Mycelial growth of the pathogen decreased as the concentration of the herbicide increased in the medium. Pyrazosulfuron ethyl at higher concentration i.e.,
40 to 70 ppm reduced the mycelial growth of the pathogen. With the progress of time the herbicide incorporated treatments did not differ significantly. In-vitro
effect of herbicides on sclerotia production revealed that there was significant difference at 4 DAI. Pyrazosulfuron ethyl at higher concentration i.e.,
30 to 70 ppm significantly reduced the sclerotia production also showing the effectiveness of the herbicide in controlling the spread of the pathogen. This result clearly indicates the suitability of the herbicide in controlling the growth of Rhizoctonia solani,
apart from its use as a rice herbicide.