Virulence and biocontrol potential of entomopathogenic nematodes against soil-dwelling stages of the small hive beetle under laboratory and semi-field conditions

BACKGROUND: The small hive beetle (SHB; Aethina tumida) is a significant pest affecting honey bees and the global beekeeping industry. The harmful effects of chemical pesticides on bee health, non-target species and ecosystems highlight the need for sustainable SHB control methods. Soil applications of entomopathogenic nematodes (EPNs) targeting the soil-dwelling life stages (wandering larvae, pupae and emerging adults) of SHB present a promising biological control approach. We conducted comprehensive laboratory experiments to evaluate the biocontrol potential of 32 Australian isolates of five EPN species (Heterorhabditis bacteriophora, Heterorhabditis indica, Heterorhabditis zealandica, Steinernema carpocapsae and Steinernema feltiae) against SHB. We also performed a glasshouse experiment testing the efficacy of nine EPN isolates in soil mesocosms that simulated field conditions. RESULTS: We demonstrated that all isolates caused mortality in all life stages, with wandering larvae the most susceptible, followed by pupae and adults. Notably, H. indica Hi.HRN caused the highest SHB mortality, while S. feltiae Sf.EG was the least effective. These isolates significantly reduced SHB adult emergence, ranging from 9%–93% in autoclaved sterile soil and 16%–59% in natural soil, suggesting interaction with other soil biota. The isolates H. indica Hi.HRN, Hi.LMBT and H. bacteriophora Hb.HIE2 were the most promising candidates for biocontrol, causing >90% corrected SHB mortality in sterile soil and >80% in natural soil. Additionally, soil application of Hi.HRN caused 33% and 43% mortality of SHB adults after their emergence from natural and sterile soils. CONCLUSION: The H. indica isolates Hi.HRN and Hi.LMBT displayed strong biocontrol potential, warranting further evaluation.