Survival Time, Mortality Rate, and Feeding Damage of Adult Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae) Exposed to Biopesticides in Laboratory Bioassays

Abstract

Survival time, percentage mortality, and feeding behavior were evaluated for adults of the weevil Myllocerus undecimpustulatus undatus Marshall (Coleoptera: Curculionidae) exposed to biopesticides by using a Petri dish plant-based bioassay system. Treatments consisted of three registered entomopathogenic fungal formulations (BotaniGard ES, PFR-97 20% WDG, and Met52 EC) and three biochemical formulations (AzaMax, Entrust, and PyGanic EC); a synthetic chemical insecticide (Sevin SL) and distilled water served as control treatments. Thirty adult M. undecimpustulatus undatus (ten per bioassay cage replicate, three replicates per treatment) were given cocoplum leaves sprayed to the point of runoff with a treatment. Survivorship of weevils was checked daily for 15 days. Five trials (15 total replicates per treatment) were performed. Survival times of weevils in all product treatments were shorter than those of weevils in the water control treatment. Percentages of beetle mortality in the Entrust and BotaniGard treatments were about two-fold higher than in the other treatments. Mean percentages of mycosis for beetles in the BotaniGard, PFR-97, and Met 52 treatments were 90%, 8%, and 5%, respectively. Weevils that consumed BotaniGard-treated leaves caused significantly more leaf damage than weevils that consumed leaves with PFR-97 or Met52. Weevils on leaves treated with Entrust, PyGanic, AzaMax, and Sevin consumed significantly less than those in the fungal and water only treatments. The high mortality rates caused by Entrust and BotaniGard suggest that populations of adult M. undecimpustulatus undatus might be well-managed using these two commercially available biopesticides. Additional testing is needed in the field to corroborate our results obtained under controlled laboratory conditions.