Behavioral and electrophysiological responses of Hylastinus obscurus to volatiles released from the roots of Trifolium pratense L.
Root volatiles from field-collected red clover plants, Trifolium pratense L., of five different ages were trapped by solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). Ethanol, E-2-hexenal, hexanal, 3-octanone, limonene and a-pinene were identified. The electroantennographic (EAG) and olfactometric responses of clover root borer, Hylastinus obscurus, to the identified compounds were studied. The GC-MS with SPME as a solvent-free collection method identified ethanol and hexanal compounds that have not previously been reported in T. pratense. The EAG experiments showed that all of the tested compounds were perceived by H. obscurus, but mixed responses were found in behavioral assays. For females, ethanol and E-2-hexenal were attractive at one or more of the tested doses, while hexanal, 3-octanone, R-limonene and S-limonene were repellent at one or more of the tested doses. Females responded to a larger number of tested compounds and a wider range doses compared to males. This behavior could reflect a more active role of females in host finding and colonization.