For the past 20 years, European honey bee (Apis mellifera) colonies in the United States have faced increasing pest pressure from invasive small hive beetles (Aethina tumida). Heavy feeding damages on A. mellifera brood and hive products are inflicted by A. tumida larvae, which leads to high volumes of fermenting larval waste and pollution of honey. Hive location by A. tumida adults is known to be heavily dependent upon volatiles emitted from A. mellifera colonies, including isopentyl acetate (IPA), which is a key component in A. mellifera alarm pheromone. Therefore, we hypothesized that A. tumida responses to IPA could be obscured by repellent molecules at the antennal level. To this end, a series of electroantennograms (EAGs) are being carried out, testing established small molecules on antennae from A. tumida adults reared in a laboratory colony. First, we examined responses to IPA (positive control for attractancy) diluted in paraffin oil (negative control) using virgin A. tumida adults aged 2-3 weeks post-emergence, to mimic the life stage at which hive seeking behavior is known to take place in the wild. After establishing an IPA dose response curve and determining an IPA half-maximal effective concentration (EC50) of 5.6 ppm, various repellent compounds are now being tested. Thus far, picaridin has been found to have an EC50 of 166,000 ppm (~17%), and picaridin is now being tested in mixes with IPA to determine the concentrations at which picaridin could obscure responses to IPA. Additionally, several heterocycle amines, including pyrrole, pyrrolidine, piperidine, and piperazine, will also be tested and compared to IPA. After EAGs are completed, olfactometry experiments will be carried out to compare antennal level responses with beetle behavioral responses. Ultimately, repellent compounds could be used in an apiary setting to mask attractive hive volatiles, preventing A. tumida adults from discovering and invading hives.

Electroantennography to measure small hive beetle (Aethina tumida) responses to established attractant and repellent molecules

ACS Fall 2021

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