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Poster: Biology & Disease Mgmt: Chemical Control


Response of Early and Late Leaf Spot Diseases on Peanut to QoI Solo Spray Programs
W. ELWAKIL (1), N. Dufault (1) (1) University of Florida, U.S.A.

Foliar diseases including rust (Puccinia arachidis), early leaf spot (ELS; Cercospora arachidicola) and late leaf spot (LLS; Cercosporidium personatum) are annual problems for southeast peanut producers. Fungicides are a critical part of an integrated management program for these devastating peanut diseases. The study objectives were to examine the efficacy of commonly used QoI fungicides for managing these diseases and to collect isolates for future pathogen population studies. Field plots of the peanut cultivar Georgia-06G were established after June 1st during 2014 and 2015 growing seasons. The fungicides azoxystrobin (Abound 2.08 SC at 18 fl oz/A) and pyraclostrobin (Headline at 9 fl oz/A) were individually applied every 12 to 17 days starting about 30 days after planting for comparison with untreated controls. Disease severity and incidence were assessed using the Florida 1-10 scale and by sampling 12 leaflets per plot. The predominant disease in 2014 was LLS and ELS in 2015. Azoxystrobin and pyraclostrobin treated plots had similar AUDPC values in 2014 and were significantly less than those of untreated plots (P ≤0.05). Mean AUDPC values were not significantly different in 2015. These results suggest that QoI fungicides have greater efficacy for LLS, however, they do not provide adequate control of ELS. Further in vitro investigations are ongoing in Florida to examine the population diversity of these pathogens and their QoI fungicide resistance profiles.