Effect of Planting Date and Peanut Cultivar on Epidemics of Late Leaf Spot in Georgia.

Field trials were conducted in 2015 and 2016 in Tifton, GA to determine the effects of planting dates (24 and 27 April, 4, 11, 19, and 26 May 2015; and 11, 18, and 25 April and 2, 9, and 16 May 2016), peanut () cultivar (Georgia-06G and Georgia-12Y), and seed treatment (nontreated and treated with azoxystrobin, fludioxonil, and mefenoxam) on epidemics of late leaf spot (), plant populations, and peanut yield. Final severity and AUDPC of late leaf spot increased with later planting dates in both years. For most planting dates in 2015 and the final planting date in 2016, final leaf spot severity and AUDPC were lower for Georgia-12Y than for Georgia-06G. Seed treatment increased plant populations for the 27 April and 4 May planting dates in 2015 and across all other treatments in 2016. Yields were higher for Georgia-12Y than for Georgia-06G in both years. In 2015, yields of both cultivars decreased according to linear functions of day of year of planting date, but there was no effect of planting date on yield in 2016. The combination of early planting with Georgia-12Y shows potential utility for management of leaf spot in situations such as organic production where fungicide use is minimal.