Control of Seed Transmission of Cylindrocladium parasiticum in Peanut with Seed Treatment Fungicides

Abstract Seeds of peanut cultivars VA 98R and NC-V11 with speckled testae were treated with fungicide and assayed on a selective medium to determine the viability of Cylindrocladium parasiticum. The fungus was isolated from 78 and 90% of the untreated speckled seed of the respective cultivars. Seed treatment with captan + pcnb + carboxin, fludioxonil, captan, and thiophanate methyl significantly reduced recovery of the pathogen in both cultivars. Speckled seed of VA 98R and NC-V11 were treated with fungicides and planted in greenhouse and/or field trials in Suffolk, VA. Plants became infected with C. parasiticum after treated and untreated speckled seed were planted in steam-treated soil in the greenhouse. In one trial, seed treatment with fludioxonil, tebuconazole, and LS 176 significantly reduced taproot colonization by C. parasiticum compared to the untreated check. In a second greenhouse trial, only fludioxonil provided significant suppression of disease. In the field, treatment with fludioxonil, thiram, and tebuconazole significantly lowered Cylindrocladium black rot (CBR) incidence compared to the untreated check. Thiram significantly reduced taproot colonization compared to all treatments except fludioxonil. Based on the present study, the addition of thiram and/or fludioxonil to the standard treatment of captan + pcnb + carboxin may offer the best protection against seed transmission of C. parasiticum.