912 Mycologia, 94(6), 2002, pp. 912–920.  2002 by The Mycological Society of America, Lawrence, KS 66044-8897 Damage and recovery from UV-B exposure in conidia of the entomopathogens Verticillium lecanii and Aphanocladium album Gilberto U. L. Braga Drauzio E. N. Rangel Department of Biology, Utah State University, Logan, Utah 84322-5305 Stephan D. Flint Department of Rangeland Resources and the Ecology Center, Utah State University, Logan, Utah 84322- 5230 Charles D. Miller Anne J. Anderson Donald W. Roberts 1 Department of Biology, Utah State University, Logan, Utah 84322-5305 Abstract: We evaluated the effects of exposure to doses supplied at an environmentally realistic in- tensity of UV-B radiation (800 mW m -2 weighted irradiance) on the culturability and germination of selected strains of the entomopathogenic Hypho- mycetes Verticillium lecanii and Aphanocladium al- bum. Increased UV-B exposure decreased relative percent culturability for all strains. Four hours of exposure to UV-B were sufficient to reduce the cul- turability close to zero. The LT 50 (50% lethal time) ranged from 120  5 min for the V. lecanii strain ARSEF 6430 to 86  14 min for the A. album strain ARSEF 6433. A strong delay in the germination of surviving conidia was observed. To determine the occurrence of photoreactivation in these two gen- era, we evaluated the effect of exposure to visible light after exposure to UV-B radiation. There was no significant difference in relative culturability be- tween conidia exposed to visible light after UV-B exposure compared to those incubated in the dark after UV-B exposure. This indicates that photore- activation, if it occurs, must have limited impor- tance in the repair of the damage induced by UV- B radiation in these two genera. Key Words: biological control, conidial germi- nation, conidial photobiology, Hyphomycetes, pho- toreactivation, UV damage Accepted for publication April 9, 2002. 1 Corresponding author, Email: dwroberts@biology.usu.edu INTRODUCTION The deleterious effects of UV radiation have been demonstrated in several genera of entomopatho- genic fungi such as Metarhizium, Beauveria, and Paecilomyces (Morley-Davis et al 1995, Fargues et al 1996, 1997, Braga et al 2001a, b, c, d). Although the Hyphomycete species V. lecanii and A. album are used for the control of various agricultural pests in different UV environments (Hall 1980, 1981, Lopez Lastra 1990, Lacey et al 1996, Steen- berg and Humber 1999, Junqueira et al 1999), little is known about the effects of UV radiation on these genera. In general, a few hours of direct exposure to a radiation of an intensity frequently encoun- tered in the environment are sufficient to fully in- activate the conidia of all the species studied. In addition to inducing inactivation, UV radiation has been demonstrated to delay the germination of sur- viving conidia (Zimmermann 1982, Moore et al 1993, Braga et al 2001a, b, c, d,). The reduction in inoculum due to conidial inactivation and the de- lay in germination are expected to reduce the ef- ficiency of these organisms as bioinsecticides in sit- uations with strong solar irradiation. Among these situations are those in which the strains are ex- posed during inoculation and/or germination to irradiances and doses above those occurring in their original habitats and to which they are not fully adapted. The reduction in the ozone layer and the consequent increase in UV-B irradiance, partic- ularly at wavelengths between 290 and 315 nm, may aggravate the problem (Caldwell and Flint 1997, Caldwell et al 1998, Madronich et al 1998, Mc- Kenzie et al 1999). We have demonstrated previ- ously that an increase in UV-B irradiance drastically reduces the culturability of conidia of various spe- cies of the genus Metarhizium (Braga et al 2001a, b, d) and that the effect of increased irradiance is greater during the growth phases in which the fun- gus is more susceptible to radiation, such as the end of germination (Braga et al 2001a). In general, attempts have been made to reduce the negative effects of UV radiation on entomopathogens by adding photoprotective agents to the formulations (Moore et al 1993, Alves et al 1998) and by select- ing strains more tolerant to radiation. Strain selec- tion has been facilitated by the wide intraspecific