INACTIVATION OF CONIDIA OF PAECILOMYCES-FUMOSOROSEUS BY NEAR-ULTRAVIOLET (UVB AND UVA) AND VISIBLE RADIATION

The detrimental effects of solar radiation, especially the ultraviolet waveband, on quiescent conidia of Paecilomyces fumosoroseus were inve stigated. Conidia were irradiated by a high-intensity source, which em itted a continuous spectrum from 270 to 1100 nm and which was equipped with long-pass filters to block short wavelengths below 280, 295, 320 , or 400 nm. After irradiation, conidia were tested for germinability, survival, and infectivity toward Spodoptera frugiperda larvae. It was demonstrated that the detrimental effects of light depended on irradi ance in the shortest wavelengths. The UVB (280-320 and 295-320 nm) app eared to be the most detrimental part of natural radiation, although U VA (320-400 nm) was also harmful. Visible and near infrared radiations were less harmful than UV. Our results demonstrate that the irradianc e of the UVB waveband should be considered as the pertinent factor for the detrimental effects of sunlight on the persistence of conidia of entomopathogenic fungi in insolated environments. (C) 1997 Academic Pr ess.