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Title: Response of new medium-maturity runner-type cultivars to fungicides for management of leaf spot diseases

item CULBREATH, A - University Of Georgia
item BRENNEMAN, T - University Of Georgia
item KEMERAIT, R - University Of Georgia
item TILLMAN, B - University Of Florida
item Holbrook, Carl - Corley
item BRANCH, W - University Of Georgia

Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2011
Publication Date: 12/15/2011
Citation: Culbreath, A.K., Brenneman, T.B., Kemerait, R.C., Tillman, B.L., Holbrook Jr, C.C., Branch, W.D. 2011. Response of new medium-maturity runner-type cultivars to fungicides for management of leaf spot diseases. Proceedings of American Peanut Research and Education Society. 43:61-62.

Interpretive Summary: not required

Technical Abstract: In the southeastern U.S., there has been a rapid transition to new peanut (Arachis hypogaea) cultivars with greater levels of field resistance to Tomato spotted wilt virus and yield potential than Georgia Green, the predominant cultivar grown since the late 1990s. However, additional information is needed on disease control inputs needed for management for fungal diseases on these new cultivars. Management of early and late leaf spot diseases caused by Cercospora arachidicola and Cercosporidium personatum, respectively, is heavily dependent on multiple applications of fungicides, with seven or more fungicide applications made in many fields. The objective of this work was to determine whether reductions number of fungicide applications might be possible with new cultivars. Whole-plot treatments consisted of 7 applications of fungicides, 4 applications of fungicides and a nontreated control. Both the 7 and 4 application treatments included four applications of mixtures of 0.20 lb ai/a of tebuconazole (Muscle 3.6F) and 0.75 lb ai/a of chlorothalonil (Bravo 720F). The 7 spray treatment had three additional applications of chlorothalonil (1.1 lb ai.a) in sprays 1,2, and 7. Sub-plot treatments in both years included Georgia Green, Tifguard, Georgia-06G, and USDA breeding line C724-19-25. In 2010, Georgia-07W, and Florun-107 were also included. Late leaf spot, was the predominant foliar disease in both years. In 2009, final Florida 1-10 scale ratings for leaf spot in nontreated plots were 8.1, 8.8, 8.3 and 8.4 for Georgia Green, Georgia-06G, Tifguard, and C724-19, respectively. In 2010, leaf spot ratings for nontreated plots were 7.6, 7.3, 6.3, 5.9, 8.3 and 7.8 for Georgia Green, Georgia-06G, Tifguard, C724-19-25, Florun-107, and Georgia-07W, respectively. Leaf spot ratings decreased with addition of 4 and 7 fungicide applications. In nonntreated plots in 2009, yield was 3596 lb/A for Georgia Green, and 4703 lb or higher for the other three genotypes. Yield for Georgia Green was 4117 and 4698 lb/A for the 4 and 7 fungicide applications, respectively whereas yields in the other three genotypes ranged from 5502 to 5678 lb/A in the 4 application treatment with no additional increase with the 7 spray treatment. In 2010, yields of Georgia Green were 3853, 5232 and 4985 for the 0, 4 and 7 application treatments respectively. Yields of the other genotypes ranged from 4619 to 5398 lb/A for nontreated plots, from 5675 lb/A to 6303 lb/A for the four spray treatment, and from 5753 to 5900 lb/A for the seven spray treatment. Although none of the new cultivars have high levels of resistance to C. personatum, all of those evaluated show potential for maintaining yield with only 4 fungicide applications.