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Assessment of Peanut Leaf Spot Disease Control Guidelines Using Climatological Data. D. E. Linvill, Agricultural Weather Office, 230 McAdams Hall, Clemson University, Clemson, SC 29634-0357. C. E. Drye, Edisto Research and Education Center, Clemson University, P.O. Box 247, Blackville, SC 29817. Plant Dis. 79:876-879. Accepted for publication 23 May 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0876.

Early leaf spot, caused by Cercospora arachidicola, and late leaf spot, caused by Cercosporidium personatum, can be controlled by foliar fungicides. Extension recommendations in South Carolina suggest planting peanuts between 15 April and 15 May. The recommended starting date to initiate 10- to 14-day fungicide spray schedules to control leaf spot is 15 June. The 1980-1990 climatological data for Sumter, Florence, and Blackville, South Carolina, were used to simulate calendar spray schedules and a method for spray timing developed at Auburn University (AUPNUT) that used observed and forecast rainfall. This simulation showed that adoption of AUPNUT scheduling in South Carolina could result in less foliar fungicide usage than the 10- and 14-day calendar-based spray schedules. The study showed: (i) the number of AUPNUT sprays depended on location in the state; (ii) the AUPNUT schedule added one application prior to 15 June on early-planted fields but averaged less than one additional spray per year for later plantings when compared to a 14-day calendar-based schedule that started on 15 June; (iii) at least one spray per year can be saved regardless of planting time, and up to Five sprays can be saved depending on the distribution of days with rain; and (iv) a simulation using historical weather data can demonstrate potential savings associated with adoption of new application schedules.