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Title: Relationships between defoliation by late leaf spot and yield in new runner-type peanut cultivars

item NAVIA GINE, P - University Of Georgia
item CULBREATH, A - University Of Georgia
item TILLMAN, B - University Of Florida
item Holbrook, Carl - Corley
item BRANCH, W - University Of Georgia
item SMITH, N - 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: Navia Gine, P.A., Culbreath, A.K., Tillman, B.L., Holbrook Jr, C.C., Branch, W.D., Smith, N.B. 2011. Relationships between defoliation by late leaf spot and yield in new runner-type peanut cultivars. Proceedings of American Peanut Research and Education Society. 43:38-39.

Interpretive Summary: not required

Technical Abstract: Early and late leaf spot caused by Cercospora arachidicola and Cercosporidium personatum, respectively, can cause severe losses on susceptible peanut (Arachis hypogaea) cultivars. Losses are primarily due to loss of peg integrity and loss of mature pods when peanut plants are inverted. Losses to both diseases have been correlated with levels of leaf spot induced defoliation late in the season. Recently, several new peanut cultivars have been released with excellent yield potential and field resistance to tomato spotted wilt virus. However, the relationship between late-season levels of defoliation by leaf spot and yield has not been characterized for these cultivars. To examine this relationship, field experiments were conducted in 2010 in Tifton. In the first experiment, four cultivars, Florida-07, Georgia-06G, Georgia-07W, and Tifguard, were combined in factorial arrangement with four fungicide treatments, 7, 4, and 3 applications of 1.1 lb ai/A of chlorothanonil (Bravo WeatherStik). All application regimes began approximately 35 days after planting, and subsequent applications were made at ca. 14 day intervals. A second trial was conducted in which these same treatments were used on Georgia-06G. Applications of 1.0 lb ai/A of flutolanil (Convoy) were made at ca. 60 and 90 days after planting in each trial to minimize effects of Sclerotium rolsii on yield. Multiple visual leaf spot ratings were made to estimate the levels of defoliation. Late leaf spot was the predominant foliar disease in both trials. Final defoliation and yield (lb/A) were determined for each plot. In the first experiment, mean final defoliation and yield for the 7, 4, 3, and 0 fungicide application regimes were 0%;5716 lb/A; 1%:5644 lb/A; 5%:5644 lb/A; and 70%;5398 lb/A, respectively for Florida-07; 0%:5753 lb/A; 0.3:5736 lb/A; 9%:5592 lb/A; and 69%:5260 lb/A, respectively, for Georgia-06G; 0%:5837 lb/A; 1%:5821 lb/A; 4%:5817 lb/A; and 49%:5471 lb/A, respectively, for Georgia-07W; 0%:5945 lb/A; 0.2%:5640 lb/A; 7%:5670 lb/A; and 64%:5748 lb/A, respectively, for Tifguard. In the second experiment on Georgia-06G, final defoliation and yield for the 7, 4, 3, and 0 application regimes were 3%:5892 lb/A; 6%:5645 lb/A; 41%:5321 lb/A; and 96%:4566 lb/A, respectively. All of the cultivars evaluated were able to maintain good yields with yield losses of less than 10% from late leaf spot, with moderate levels of final defoliation. Losses in yield in Georia-06G were only 33% where final defoliation was much higher. Additional evaluation of disease and yield loss relationships and economic aspects associated with those are in progress.