Electroantennogram responses of the asparagus moth, Parahypopta caestrum (L.), to host-plant volatiles

The asparagus moth, Parahypopta caestrum (Hübner) (Lepidoptera, Cossidae), is one of the most damaging pest of Asparagus spp. in many Mediterranean areas, including the Foggia province, the widest producing area of green asparagus in Italy. The soil-borne larvae of this pest bore galleries into the roots and the shoots causing the destruction of plantations after 2-3 years. Due to the cryptic nature of the immature stages in the soil, control of this pest is very difficult. Plant volatiles play an important role in mate and host location in phytophagous insects. To contribute to the knowledge of P. caestrum chemoreceptivity, male and female electroantennographic (EAG) responses to 28 host plant volatiles were recorded. At the 1 mg dose, all compounds elicited measurable EAG responses. In both sexes, (Z)-3-hexen-1-ol, sulcatol, (E)-2-hexenal, 1-octen-3-ol, linalool, terpineol, and 2-heptanone were the most EAG-active compounds whereas α-copaene, aromadendrene, and hexadecene were the weakest antennal stimulants. Among all compound tested, males showed a significantly higher mean EAG response than females to (Z)-3-hexenol (P < 0.05, t-test). This compound elicited dose-dependent EAG responses in both sexes indicating the sensitivity of the peripheral olfactory systems to changes in stimulus concentration. Field trapping tests are in progress to evaluate the behavioural activity of the most EAG-active compounds alone and in different combinations. Elucidation of the sensitivity profile of adults to asparagus volatiles provides a basis for future identification of bioactive compounds useful for developing semiochemical-based control strategies for this pest.