Mechanisms involved in mating disruption in Sesamia nonagrioides Lefebvre by Sesaline (R).

S. nonagrioides, the corn stalk borer is one of the most important pests on maize crops all around the Mediterranean countries. Since several years, f ield trials on mating disruption were carried out on large scale against th is pest. The sprayable formulation, Sesaline(R), tested during summer 1997 in south of France consisted of the two main components of S. nonagrioides sex pheromone. In order to better understand the mechanisms involved in the disruption of the chemical communication between males and females, two st udies were carried out on male behaviour in wind tunnel. The test serie n d egrees 1 aims at studying the attractiveness of Sesaline(R) by itself. The test serie n degrees 2 aims at determining the disruption potentialities of Sesaline(R) when male were stimulated by a pheromone gland. The amounts of Sesaline(R) applied range from 10 ng to 1 mg. The first serie showed that both doses of Sesaline(R), 100 ng and 1 mu g, induced a moderated attractio n characterised by a low percentage of source contact. For up and below dos es none source contact was observed. The second eerie evidenced two thresho lds of Sesaline(R) doses that have an effect upon male responses when stimu lated by a pheromone gland : at 100 ng a significant decrease in attraction behaviour was observed; at 10 mu g, mates were nor able to initiate attrac tion. This last dose disrupted completely attraction behaviour. The present study in laboratory confirmed the results obtained in the field : Sesaline (R) presented a strong capacity in disrupting chemical communication betwee n males and females; Sesaline(R) was found to be a poor attractant for male s. In consequence, attraction of the males from outside of Sesaline(R) trea ted field is unlikely.