Responses of Rhynchophorus ferrugineus adults to selected synthetic Palm esters: electroantennographic studies and trap catches in an urban environment

The Red Palm Weevil (RPW), Rhynchophorus ferrugineus Olivier, accidentally introduced in the European countries facing the Mediterranean basin, is becoming the most serious pest for ornamental palms in the urban environment. In our work we tested electroantennogram (EAG) and behavioural responses of RPW adults to five selected synthetic palm esters: ethyl propionate, ethyl butyrate, ethyl isobutyrate, ethyl lactate and ethyl acetate. EAG bioassays showed higher sensitivity of female antennae compared to male antennae for test compounds. Differences were also recorded in the EAG responses using different esters and doses. Ethyl propionate was the synthetic ester that elicited the strongest relative EAG response from both sexes. For all the synthetic esters, the weakest EAG response was recorded at the dose of 0.1 μg. RPW behavioural responses in the urban environment were evaluated over six biweekly observations on pheromone baited traps. Results showed that pheromone baited traps supplemented with either 10% (v/v) solution of ethyl propionate and 10% (v/v) solution of ethyl acetate caught more adults than pheromone traps baited with only ethyl propionate, while there were not different catches between pheromone baited traps supplemented with ethyl propionate or ethyl acetate. This study support the application of the mass trapping implemented with palm esters as a potential tool for the management of RPW populations to protect ornamental palms in urban environments.