Evaluation of entomopathogenic fungi in biocontrol of Aethina tumida (small hive beetle)

Abstract

Small hive beetle (SHB) (Aethina tumida) is considered a scavenger and parasite of honeybees and their colonies especially outside of its native habitats. Larvae of A. tumida consume honeybees’ eggs, broods, pollen, and honey, causing a substantial destruction. To control the beetle, chemical pesticides are commonly used. However, this leads to the emergence of pesticide resistance and this also affects the honeybees as well as and the human health. Therefore, investigation of eco-friendly biological control methods is essential. A. tumida has been recorded recently in Kegalle, Sri Lanka, and this research aimed to evaluate entomopathogenic fungi as potential biological control agents of the beetle. Entomopathogenic fungi species were isolated using two methods: 1. the isolation of fungi from soil using greater wax moth larvae as the bait and 2. the use of natural insect cadavers with visible mycosis. In method 1, larvae were heat treated and placed on soil to prevent excessive webbing. Infected cadavers were placed on PDA containing amoxicillin. Emerging fungi were isolated, purified, and tested for pathogenicity with A. tumida adults and larvae. Treatment groups (n = 20) were tested by dipping for 3 seconds in 108 spore suspension, which was determined by hemocytometer and the control group (n = 20) was tested by dipping for 3 seconds in distilled water. Two out of five fungal species, namely sp1 and sp2, showed 100% mortality of the adults in eight days (p ≤ 0.001). All five fungal species had shown mortality in wandering larvae of the beetle among which four isolated fungal species had shown 100% mortality. Fungal sp1 and sp2 showed 100% mortality from 48 hours (p ≤ 0.001). Further investigations on the identification of fungal species, and the field trials on the control of A. tumida and the effects on non-target organisms are recommended.