COMMERCIAL FUNGICIDE USE FOR LEAFSPOT CONTROL ON A PARTIALLY-RESISTANT PEANUT (ARACHIS-HYPOGAEA L) CULTIVAR

Peanut cultivars Southern Runner, partially resistant to late leafspot caused by Cercosporidium personatum (Berk. & Curt.) Deighton, and Sunrunner, susceptible to late leafspot, were planted in adjacent tests in 1984 and 1985. The commercially available fungicides chlorothalonil, triphenyltin hydroxide plus sulfur, mancozeb plus sulfur, cupric hydroxide plus sulfur, and captafol were applied for leafspot control. Late leafspot was the predominant foliar disease in the test. Yield losses with no disease control varied from 26 to 40% with Southern Runner and from 68 to 74% with Sunrunner over the 2 yr of testing. Chlorothalonil applied in a full-season, seven-spray program controlled leafspot and resulted in the highest yields of all treatments. Chlorothalonil applied in a delayed-20-d interval program (initiated at 61 DAP in 1984 and 67 DAP in 1985), gave better disease control than the other fungicides in a full-season program. While conducting these tests it was discovered that Southern Runner is susceptible to zinc deficiency and this factor may explain low yields in 1985.