Management Tactics that Complement Host Resistance for Control of Cylindrocladium Black Rot of Peanuts1,,2

Abstract

Abstract Peanut (Arachis hypogaea L.) genotypes were evaluated in field microplots infested with Cylindrocladium crotalariae (Loose) Bell and Sobers. In experiment I there were three genotypes, two inoculum densities, and two levels (0, 100 kg/ha) of nitrogen (N) fertilizer. A non-nodulating peanut genotype was less susceptible to C. crotalariae than either of its nodulating parents. Application of N to the nodulating parents decreased disease severity if inoculum density was low. Application of N to the non-nodulating line increased disease severity compared to disease in unfertilized plots of the non-nodulating line. Experiment II evaluated effects of cultivar (susceptible Florigiant, resistant NC 8C), two inoculum denities, N fertilizer [0, 100 kg/ha), and high carbon:nitrogen organic matter amendment (0, 400 kg/ha). Root rot severity was reduced if the cultivar was resistant, if inoculum density was low, and if N was applied. Soil amendment did not affect disease severity. In experiment III, planting date effects on disease severity were evaluated on resistant NC 8C and resistant NC 18016. Planting on May 2, when minimum soil temperature was below 18 C, resulted in more severe disease than planting on May 17, or May 30, 1983 when minimum soil temperature was above 18 C. Benefits of combining management tactics of resistance, preventing high inoculum densities, N management, and proper planting date are discussed.