LEAF CONSUMPTION BY LARVAE OF THE COLORADO POTATO BEETLE (COLEOPTERA,CHRYSOMELIDAE) INFECTED WITH THE ENTOMOPATHOGEN, BEAUVERIA-BASSIANA

In a laboratory feeding experiment, we used a photometric method to st udy the effect of the entomopathogenic hyphomycete, Beauveria bassiana (Balsamo) Vuillemin, on foliage consumption by fourth-instar Colorado potato beetles, Leptinotarsa decemlineata (Say). Three inoculum rates (10(4), 3 x 10(4), and 10(5) conidia/cm2) were tested, causing time-m ortality responses ranging from 6 to 12 d. During the first 24 h of ex posure to any of the three rates, larvae contaminated with B. bassiana expressed significant phagostimulation, that reached 20%. We found no significant differences in consumption rates on day 2. After this per iod, infection caused starvation such that early consumption by inocul ated larvae was significantly less than that of control larvae. Moreov er, increasing the fungus rate decreased the length of the feeding per iod. Finally, the reduction in total food consumption per larva caused by the B. bassiana treatment was 56.6, 67.8, and 76.2% for the three rates tested.