Survival of Cercospora sojina causing frogeye leaf spot of soybean and impact of weather factors on thedisease development

摘要

Frogeye leaf spot (FLS) caused by Cercospora sojina Hara is occurring in epidemic form in soybean growing areas in sub-humid mid hill agro-ecological zone of Himachal Pradesh and has emerged as one of the major diseases, causing considerable yield losses. So, present investigations were carried to know the perpetuation of pathogen, weather factors in disease development and assessment of yield losses. The survival of the pathogen inoculum was observed on infected plant debris kept on the surface as well as buried in soil at 10 and 20 cm depth under natural field conditions. The inoculum remained viable up to 10 months on infected plant parts thus, debris plays an important role as a source of primary inoculum. A strong negative correlation was observed between viability of pathogen and depth of burial of infected debris in field. Positive and a strong multiple correlation was observed between disease severity and weather variables (temperature, relative humidity and sun shine). Assessment of yieldlosses due to disease revealed that pathogen infection at growth stage R, (first flower anywhere on plant) and P. (first pod on upper nodes of plant) were found critical stages resulting in significant yield losses.