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 study the effect of the entomopathogenic hyphomycete, Beauveria bassiana (Balsamo) Vuiilemin, on foliage consumption by fourth-instar Colorado potato beetles, Leptinotarsa decemlineata (Say). Three inoculum rates (104, 3 × 104, and 105 conidia/cm2) were tested, causing time-mortality responses ranging from 6 to 12 d. During the first 24 h of exposure 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 period, infection caused starvation such that early consumption by inoculated larvae was significantly less than that of control larvae. Moreover, increasing the fungus rate decreased the length of the feeding period. 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.