Disruption of Sex Pheromone Communication in Chilo Suppressalis with Pheromone and Analogs

Abstract

Chilo suppressalis (Walker) is the most important species of several rice borers in the genus Chilo (Pyralidae) in Asia. The sex pheromone of this species was previously identified from females as a mixture of 2 homologous aldehydes, (Z)-ll-hexadecenal (Z-ll- HDAL), and (Z)-13-octadecenal (Z-13-0DAL) (Nesbitt et al., 1975; Ohta et al., 1976). We then initiated research on the application of the sex pheromone for control of this pest. Factors affecting the attractiveness of the synthetic pheromone have been examined in the field (Tatsuki et al., 1979), and pheromone release rate was shown to be a critical factor for attraction of males. Namely, rubber septa loaded with 1 or 2 mg of the pheromone (5:1 mixture of Z-11-HDAL and Z-13-ODAL) were attractive, while 0.1 or 10 mg dispensers showed almost no activity. These results indicated that the release rate of pheromone for male attraction was narrow, and suggested that mating disruption may be a profitable approach for direct control of C. suppressalis. Because aldehydes are very unstable in the field, we attempted to identify disruptants with more stability than the pheromone components from structurally related compounds. We synthesized the sex pheromone and 12 analogs including compounds having the same alkyl moieties as the pheromone components and other functional end groups; i.e., alcohol, acetate, and methyl groups.