Sitona lineatus Host-Plant Odors and Their Components: Effect on Locomotor Behavior and Peripheral Sensitivity Variations

Adult Sitona lineatus L., (Coleoptera: Curculionidae) feed on the leaves of various species of leguminous plants, and females lay in the vicinity of pea plants, the roots of which are eaten by the larvae. A study of the volatiles from several legumes and of the response of S. lineatus individuals to these substances was undertaken using two complementary techniques: behavioral, to study the locomotory orientation; and electrophysiological, using electroantennography (EAG). Four volatile compounds, cis-3-hexen-1-ol, 2-hexenal, cis-3-hexen-1-yl acetate, and 3-octanone, were identified from pea, vetch, clover, and lucerne, by coupled gas chromatography–mass spectrometry (GC-MS) and coupled gas chromatography–infrared spectrometry (GC-IR). After emergence from July to mid-November, the imago display high response to the odor of pea and some other leguminous plants. A second period of enhanced sensitivity was observed during crop colonization from March to May. High EAG response to pea odor and cis-3-hexen-1-yl acetate was correlated with periods of enhanced locomotory orientation during these months. Experimental results indicate that cis-3-hexen-1-yl acetate could play a key role in discriminating pea among other acceptable leguminous species.