Optimizing Feeding and Pupation Bioassays to Assess the Effects of Insecticidal and Repellent Treatments on Aethina tumida Larval Development and Pupation Success.

Abstract

European honey bee (Apis mellifera) colonies are an ideal host to the invasive beetle Aethina tumida, providing a nutrient rich environment that is protected from the elements and facilitates beetle reproduction. Although various management techniques and chemical treatments for A. tumida have been developed, understanding the efficacy of these treatments and techniques is limited. Throughout this study, several methods for impairing A. tumida development and delivering insecticidal, repellent, or antifungal treatments were examined. A series of A. tumida larval feeding bioassays developed and optimized feeding gel pellet for delivery of insecticidal treatments, revealing that A. tumida larvae are sensitive to the two common in-hive varroa mite (Varroa destructor) treatments: coumaphos (EC₅₀ = 25.6 ppm) and tau-fluvalinate (EC₅₀ = 21.2 ppm). Feeding bioassays also demonstrated that A. tumida were more sensitive to the pyrethroid compounds permethrin (EC₅₀ = 3.37 ppm), deltamethrin (EC₅₀ = 2.69 ppm), and bifenthrin (EC₅₀ = 0.365 ppm), which have been previously used to control this beetle. Feeding bioassays also revealed that the antifungal drug Amphotericin B was palatable to A. tumida larvae via feeding, but was also injected into A. tumida larvae and adults. Two types of pupation bioassays were also developed to test the effects of several insecticidal and repellent treatments on pupation burrowing and pupation success. Overall, this work details specific toxicity information regarding common insecticidal treatments found in the apiary setting study and provides groundwork and methods for testing insecticidal compounds on A. tumida larvae in in the future.