Weather patterns associated with sporulation of Oncobasidium theobromae on cocoa

Abstract

Spore release was highly correlated with the number of consecutive hours of basidiome wetness. If basidiomes were wet for 5 h or less, no spores were released. Sporulation increased progressively as the period of basidiome wetness increased from 5 h, reaching a maximum at 12 h. Spore release was highly correlated with the number of rainy days, but the number of spores released showed no correlation with rainfall volume. Dew deposition induced sporulation in the absence of rain, provided the basidiome was exposed to the sky. However, only small numbers of spores were released and their development was limited. Laboratory studies using field-collected basidiomes revealed that sporulation required an alternating light and dark cycle, and that spores were only released during the dark period. If during the dark period the temperature exceeded 26 °C, or the relative humidity fell below 95%, or if the basidiome was not initially wetted, no spores were released.