Institut de Recherche sur la Biologie de l'Insecte, UPRESA-CNRS 6035, Faculté des Sciences, Parc de Grandmont, 37200 Tours, France.
Sitona lineatus (Coleoptera: Curculionidae) is one of the most important pest of pea crops in France. Adults feed on the leaves, while larvae eat root nodules containing bacteria Rhizobium leguminosarum. Regular caughts in two juxtaposed crops showed that in March-April, most of the adults leave clover to pea, where egg laying occurs. However, few insects stay and reproduce in clover. EAG and olfactometer tests showed that weevils are not more strongly stimulated by pea odor than by clover odor. Nevertheless, feeding tests indicated that pea leaves are preferred to clover ones, whatever the period of the year. The release of the aggregation pheromone, the 4-methyl 3,5 heptanedione, identified by Blight et al. (1991) was investigated by GC and EAG. The males start to release pheromone from March, before spring migration, and in April, when they have colonized pea crops. Thus, the pheromone seems to play an aggregation role towards a feeding/oviposition site rather than a sexual role, all the more since almost 100 percent of females are already inseminated at the end of winter.