Management of Early Leaf Spot of Peanut with Pyraclostrobin as Affected by Rate and Spray Interval

Abstract

Field tests were conducted in Tifton, Georgia, in 1998 to 2000 and in Plains, Georgia, in 1999 and 2000 to determine the efficacy of pyraclostrobin on early leaf spot (Cercospora arachidicola) of peanut (Arachis hypogaea). Application regimes included three rates (112, 168, and 224 g a.i./ha) of pyraclostrobin applied on 14-, 21-, and 28-day schedules. These were compared to currently-used fungicides chlorothalonil, tebuconazole, and azoxystrobin. In all tests, application of pyraclostrobin at rates of 168 g/ha or higher gave better leaf spot control than chlorothalonil applied at 1.26 kg/ha or tebuconazole applied at 227 g/ha on the same schedule. At both Plains and Tifton, plots treated four times with pyraclostrobin at 168 or 224 g/ha on a 28-day schedule had final leaf spot intensity ratings that were similar to those of standard rates of chlorothalonil or tebuconazole applied seven times on a 14-day schedule. At Tifton, all three rates of pyraclostrobin applied five times on a 21-day schedule had final leaf spot ratings lower than those of plots treated with seven applications of chlorothalonil or tebuconazole on a 14-day schedule. There was little improvement in leaf spot control with rates of pyraclostrobin higher than 168 g/ha in any test or application schedule. Fungicide effects on yield were not consistent, but in all tests, yields from plots treated with any of the three rates of pyraclostrobin were similar to or higher than yields from plots treated with 227 g/ha of tebuconazole on the same schedule. The ability to use pyraclostrobin at 21-day intervals and maintain control of early leaf spot similar to that of application of currently available fungicides at 14-day intervals represents potential savings in time, fuel, labor, and equipment costs. Accepted for publication 14 October 2002. Published 18 October 2002.