VARIABILITY IN SUSCEPTIBILITY TO SIMULATED SUNLIGHT OF CONIDIA AMONG ISOLATES OF ENTOMOPATHOGENIC HYPHOMYCETES

The influence of simulated sunlight on survival of conidia of 4 specie s of entomopathogenic Hyphomycetes was investigated. Conidia from 65 i solates of Beauveria bassiana, 23 of Metarhizium anisopliae, 14 of Met arhizium flavoviride ide and 33 isolates of Paecilomyces fumosoroseus were irradiated by artificial sunlight (295 to 1,100 nm at an ultravio let-B irradiance of 0.3 W m(-2)) for 0, 1, 2, 4 and 8 h. Survival was estimated by comparing the number of colony forming units (CFU) produc ed by conidia exposed to irradiation to the number of CFUs produced by an unexposed control. Survival decreased with increased exposure to s imulated sunlight; exposure for 2 h or more was detrimental to all iso lates tested. Overall, isolates of M. flavoviride were the most resist ant to irradiation followed by B. bassiana and M. anisopliae. Conidia of P. fumosoroseus were most susceptible. In addition to the large int erspecies differences in susceptibility to irradiation, there was also an intraspecies variation indicating that strain selection to irradia tion tolerance may be important in the development of microbial contro l agents where increased persistence in an insolated environment is de sirable.