Role of wind and rain in dispersal of Botrytis fabae conidia

Numbers of Botrytis fabae conidia dispersed in plots of winter-sown field beans in which chocolate spot developed were monitored with vertical cylinder and horizontal slide samplers exposed within crops for 3- or 4-day periods. Cylinders collected more conidia than slides before stem extension of the crop; later slides collected more conidia than cylinders. The greatest numbers of conidia were collected by slides during periods in June or July when there was heavy rain. On dry days between mid-May and mid-July a Burkard sampler collected most conidia in the morning when wind speed was increasing and relative humidity was decreasing. On wet days during this period, there were smaller maxima in numbers of conidia collected during heavy rain.