The effect of temperature on colonization of Cercosporidium personatum leafspot of peanuts by the hyperparasite Dicyma pulvinata

Abstract

Colonization of lesions of Cercosporidium personatum on detached peanut leaflets by the hyperparasite Dicyma pulvinata followed a logistic growth curve. The initial colonization rate and the asymptotic level of colonization were estimated by plotting the calculated relative rate of colonization against the percentage colonization. These two parameters and a subjective estimate of the time-lag in colonization were used to compare colonization of lesions, in the dark, by the hyperparasite at constant and cycling temperature regimes. No colonization was observed at constant temperatures ⩾31.5°C. The time-lag in colonization increased and the asymptotic level declined markedly at constant temperatures >28°C. At cycling temperature regimes, the initial colonization rate and the asymptotic level of colonization were directly related to the difference between maximum and minimum temperatures, especially at maximum temperatures >28°C.