Will the application of biocontrol fungi disrupt predation of Acanthococcus lagerstroemiae by coccinellids?

Insect predators are the most important natural enemies of the crapemyrtle bark scale (CMBS) in the USA. Mycopesticides (biocontrol fungi) are considered an IPM tool to increase CMBS mortality; however, their impacts on CMBS predators are unknown. The objectives of this study were to assess the abundance and diversity of CMBS natural enemies in Louisiana; evaluate the impacts of mycopesticides on survival of CMBS predators by life stage; and determine if entomopathogenic spores delivered to crapemyrtles are transferred to predators under field conditions. The mycopesticides Ancora (R) (Isaria fumosorosea PFR97), BioCeres (R) (Beauveria bassiana ANT03), and BotaniGard (R) (B. bassiana GHA) were tested against the coccinellids Chilocorus spp. and Hyperaspis bigeminata under laboratory and field conditions. Adults and larvae of the coccinellids were treated with each mycopesticide and survival recorded over a 14-day period. The most common natural enemies on CMBS infested trees were the coccinellids Chilocorus cacti, C. stigma, and Hyperaspis bigeminata (Coleoptera: Coccinellidae). In laboratory bioassays BotaniGard (R) reduced survival of adults and larvae of both genera by at least 57%. BioCeres (R) reduced the survival of Chilocorus spp. adults by 40% and Ancora (R) reduced survival of H. bigeminata larvae by 69%. Under field conditions, CMBS infestations were sprayed with the mycopesticides and coccinellids were collected every other day for a two-week period. Spores of the applied mycopesticides were recovered from the coccinellids; however, it is not known if infection occurred in the field trial or spores were delivered to CMBS infestations by the coccinellids. We conclude that mycopesticides negatively impacted the survival of coccinellids in laboratory trials, and coccinellids can transport pathogen spores under field conditions.

Automated summary

This study assessed the abundance and diversity of CMBS natural enemies in Louisiana and evaluated the impacts of mycopesticides on the survival of CMBS predators. It was found that ladybugs can transport pathogen spores under field conditions.