Wind dispersal of conidia of Botrytis spp. pathogenic to Vicia faba

Increasing numbers of conidia were blown from sporulating cultures of Botrytis fabae and B. cinerea as windspeed increased up to 10 m/s. Partial drying of cultures increased the number of spores blown away at low and intermediate windspeeds. Release of spores at a constant windspeed was sustained over a prolonged period. Different patterns of release from colonies of the two species when windspeed was gradually increased, or at a constant windspeed. may be related to differences in spore size affecting the drying rate. Many conidia of both species were released as clumps. A higher proportion of B. cinerea than B. fabae conidia were clumped, partly because the mean number of spores per clump was greater. Individual conidia fell more slowly in still air than did clumps. The humidity in a bean crop was more favourable to development of Botrytis lesions than that above the crop. Low windspeeds measured within crops may restrict dispersal of conidia and may result in uneven distribution of chocolate spot lesions.