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Poster: Diseases of Plants: Crop Loss Assessment


Effect of planting date and peanut cultivar on leaf spot epidemics and pod yield
B. JORDAN (1), A. Culbreath (2), W. Branch (3) (1) University of Georgia, Dept. of Plant Pathology, U.S.A.; (2) University of Georgia, Dept of Plant Pathology, U.S.A.; (3) University of Georgia, Dept. of Crop and Soil Science, U.S.A.

Planting date can affect the risk of losses to early and late leaf spot caused by, Cercospora arachidicola and Cercosporidium personatum, respectively, of peanut,Arachis hypogaea, in both conventional and organic systems. The objective of this study was to characterize the effect of planting date on leaf spot epidemics and yield in new cultivars with moderate tolerance to these diseases. A field trial was conducted in 2015 in Tifton, GA. Treatments were six planting dates (24 and 27 April, 4, 11, 19, and 26 May) arranged factorially with two cultivars, Georgia-06G and Georgia-12Y. Experimental design was a randomized complete block design with 4 replications. No foliar fungicides were applied. Late leaf spot was the predominant disease. Epidemics were severe in plots planted at the later dates. Final leaf spot ratings (Florida 1-10 scale) and AUDPC increased linearly with later planting date (Julian day) for both cultivars. Yield of Georgia-06G decreased linearly, and yield of Georgia-12Ydecreased according to a quadratic function with later planting. For most planting dates, final leaf spot severity and AUDPC were lower, and yield was higher for Georgia-12Y than for Georgia-06G. The combination of early planting with Georgia-12Y shows potential for reducing risks of losses, leaf spot, and maximizing yield in situations such as organic production where fungicide use would be minimal.