EFFECT OF TEMPERATURE AND RELATIVE-HUMIDITY ON DEVELOPMENT OF CERCOSPORIDIUM-PERSONATUM ON PEANUT IN GEORGIA

In controlled environment experiments, a minimum of 4 hr of relative h umidity greater than or equal to 95% per day was required for conidial production by Cercosporidium personatum, and the highest numbers of c onidia were produced when lesions were subjected to daily periods of 1 6 or more hours of relative humidity greater than or equal to 95%. The optimum temperature for spore production was near 20 C. In field stud ies, numbers of airborne conidia of C. personatum, the causal agent of peanut late leaf spot, were monitored with Burkard 7-day recording vo lumetric spore traps at Athens, Plains, and Tifton, Georgia, in 1986-1 988. Trapping of conidia was initiated in mid-July to early August, wh en late leaf spot lesions were first detected. A diurnal periodicity i n spore release was observed, with peak spore catches occurring betwee n 10 A.M. and 6 P.M. Conidia were detected on most days during the tra pping period. For the years and locations examined, duration of relati ve humidity greater than or equal to 95% generally exceeded 5-hr durat ion each day and temperatures seldom dropped below 20 C, indicating th at conditions in Georgia were generally favorable for spore production .