Effect of Isaria fumosorosea Wize on survival and leaf consumption of Microtheca ochroloma Stål (Coleoptera: Chrysomelidae)

Microtheca ochroloma, commonly known as the yellowmargined leaf beetle, causes significant losses on organically produced crucifers in the southern United States. Pest management methods that can be implemented in organic production systems, such as biological control using entomopathogenic fungi, might help to maintain the populations of this pest below economically damaging levels. The fungus Isaria fumosorosea has shown low efficacy against M. ochroloma adults when applied directly on the beetle, but no information has been reported about its effect on leaf consumption. This study evaluated the effect on survival and consumption of M. ochroloma adults when fed leaves sprayed with I. fumosorosea. Ten bok choy plants were sprayed with one of four concentrations: 0.1, 0.5, 1, and 2 g of desiccated granules of the formulation PFR-97 per 100 ml of distilled water. Ten control plants were sprayed with distilled water only. Six adults were placed on each plant and the number of dead beetles was counted daily for 7 days. Four leaves from the center of the plant were removed, and the area consumed by the beetles was measured using the software ImageJ. No significant differences were found with adult mortality among the treatments or between the fungal treatments as a whole and the control. However, plants sprayed with 0.5 and 1 g/100 ml of water suffered significantly less damage than the control. Control plants had on average 3.7% more damage than the treated plants. Further evaluations should be done to determine any effect of I. fumosorosea on larval consumption.