Electrophysiological and behavioural responses of coconut black beetle (Oryctes rhinoceros L.) (Coleoptera: Scarabaeidae) to selected plant volatiles

Abstract

Rhinoceros beetle (RB) (Oryctes rhinoceros L.) is one of the devastating pests of coconut and other palm species. The main strategy for the management of RB is the use of highly toxic synthetic pesticides. However, banning of toxic pesticides in Sri Lanka urges finding alternative repellant materials. The use of semiochemicals especially behaviour-modifying plant volatiles is a recent trend in agriculture pest management. Therefore, this study was conducted to identify the repellent plant volatiles to formulate a semiochemical-based pest management strategy. Electroantennographic (EAG) technique employed to explore the antennal response of male and female RB to 12 plant volatiles using a commercially available EAG system. Results revealed that mean antennal responses were significantly higher (p<0.05) on both males and females to plant volatiles than control. The largest response evoked by aggregation pheromones (Male 0.7698 ± 0.130 mV, Female 0.9504 ± 0.232 mV) then evoked the higher responses by the male to Ethyl butyrate, Limonene (+), 1-Octane-3-ol, α-pinene, and Propyl butyrate. Whereas female evoked higher responses to 1-Octane-3-ol, Limonene (+), Citronella, and 3-Hexene-1-ol. The dose-response study indicated the male responses had decreasing trend with increasing doses from 1% to 10%, while the female was erratic. Moreover, dual choice olfactometer studies revealed that males and females were attracted to RB aggregation pheromone, Limonene (+), Ethyl propionate, and β-Myrcene where they were repelled by Citronellol, 2-hexane-ol, 1-Octane-3-ol, and α- Pinene. Therefore, Citronellol, 2-hexane-1-ol, α- Pinene and 1-Octane-3-ol, can be used as a potential plant volatile to formulate the repelling compounds to manage the O. rhinoceros.