Evaluation of Apicure, a plant-based extract for the management of the small hive beetle, Aethina tumida

Abstract

The honey bee, Apis mellifera Linnaeus (Hymenoptera: Apidae) is a major pollinator of agricultural crops. However, this role has been threatened by the small hive beetle (SHB) Aethina tumida Murray (Coleoptera: Nitidulidae), an invasive pest of honey bees due to their capacity to significantly affect the health of honey bees. This study sought to evaluate the potential of Apicure, a plant -based extract developed at the International Centre for Insect Physiology and Ecology (icipe) for the management of honey bee pests. In addition, an in-depth understanding of the volatile organic compounds of Apicure and the mode of action of this novel product against the small hive beetle, A. tumida were provided. To achieve the objectives, firstly, headspace volatiles of Apicure were collected using super Q adsorbent traps. Secondly, the volatiles were analyzed using Gas Chromatography–Mass Spectrophotometry (GC-MS) to ascertain the constituent compounds of Apicure. Thirdly, the selectivity and sensitivity of antennal receptors of A. tumida adults to the volatile compounds of Apicure was established with the coupled Gas Chromatography-Electroantennographic Detection (GC-EAD). Finally, dual-choice bioassays were carried out in a Y-tube olfactometer to determine the behavioral activity of this product and its electrophysiologically active constituents. GC-MS analyses identified 40 compounds in Apicure. Out of these, 11 compounds that elicited antennal responses to SHB antennae in electroantennography studies. These included camphor, limonene, camphene, cymene, cymenene, α-terpineol, geraniol, α-Farnesene caryophyllene oxide, linalool and terpinen-4-ol. Y-tube olfactometer bioassays established that Apicure is a repellant to SHB. Behavioral assays with single synthetic standards showed that linalool, camphor, geraniol, and α-terpineol are repellants while limonene is an attractant to SHB. These results signify the potential role of the Apicure and its components as repellants and attractants in SHB management. This product can also be used to mask the in-hive small hive beetle attractants hence reducing the colony invasion by beetles as they use these chemical cues to locate their host.