Laboratory observations on the effect of humidity on the persistence of infectivity of conidia of the aphid pathogen Erynia neoaphidis

SUMMARY Conidia of the aphid pathogen Erynia neoaphidis on detached bean leaves and glass coverslips maintained at 20°C and at humidities from 40 to 100% r.h. lost their infectivity for pea aphids at a rate dependent on the humidity. Infectivity declined most rapidly in inocula kept on leaves at 70% r.h. and persisted longest in those at 40 and 50% r. h. That of inocula on coverslips declined most rapidly at 77% r.h. and persisted longest in those kept at 40% r.h. Even after 21 days a little infectivity was retained by conidia stored at 50% r.h. on leaves and 40% r.h. on coverslips.