Responses of Peanut Genotypes to Fungicidal Control of Early Leaf Spot in Malawi1

Abstract

Abstract Early leaf spot (Cercospora arachidicola Hori.) is the most destructive disease of peanut (Arachis hypogaea L.) in Malawi. Fifteen peanut genotypes were examined for their response to fungicidal control of early leaf spot during the 1990/91 (year 1), 1991/92 (year 2), and 1992/93 (year 3) growing seasons at Chitedze, Malawi. Total rainfall and its distribution in these years were variable, with the most favorable pattern in year 3. Early leaf spot was most severe in year 2, although there was a severe midseason drought during this year. Fungicide application gave excellent control of the disease in all growing seasons. The cultivar Malimba had the most damage and the breeding line ICGV-SM 85053 had the least damage from early leaf spot. Pod yields were higher in year 3 than in the other two growing seasons. Pod yields were significantly higher in fungicide-sprayed (treated) plots than in water-sprayed (control) plots in years 1 and 3. Most peanut genotypes had positive yield responses to disease control in years 1 and 3. However, there were no significant differences in pod yields between treated and control plots of most genotypes in year 2. Although the pod yields were lower in year 2 than in year 1, total biomass production was higher in year 2. It was apparent that biomass partitioning was severely affected in year 2 due to the midseason drought stress that reduced pod yields and vitiated the beneficial effects of fungicidal application. Investment in fungicidal control of early leaf spot on genotypes with low yield potential may not be economical under less than optimal rainfall conditions.