Over the years 1957-62 it was established that high rainfall and long periods of high relative humidity, both occurring as much as 30 days before the beginning of fruit picking, were correlated with high incidence of fruit grey mould (Botrytis cinerea Pers. Ex Fr.) in strawberries of the susceptible variety Talisman. Such conditions can apparently result in the establishment of latent infection in the young fruits. In raspberries of the susceptible variety Mailing Exploit no such correlations were established except for the 5-day period immediately before picking, but a correlation was found between high incidence of fruit grey mould and high rainfall during a 10-day period of the picking season.
In both crops high incidence of grey mould is associated with long intervals between picking dates, and, within these intervals, long persistence of surface water films.
In the case of the strawberry Talisman, it is suggested that relatively simple meteorological data obtained as long as 30 days before the estimated beginning of picking could be used in forecasting grey mould epidemics. It is further suggested that the effect of wet weather in both strawberries and raspberries may lie to some extent in its influence on the physiology of the latently-infected fruit at the rapid ripening stage, as well as in its influence on the initiation of infections of flowers from spores and of ripe fruit from saprophytic sources.