Electrophysiological and Behavioral Responses of Spotted Stem Borer, Chilo partellus, to Sex Pheromone Components and Their Blends.

The spotted stem borer, Chilo partellus (Lepidoptera: Crambidae) is the major insect pest of maize and sorghum crops during the rainy season. The pheromone released by adult virgin females has been reported to consist of (Z)-11-hexadecenal (Z11-16:Ald) as major component and (Z)-11-hexadecenol (Z11-16OH) as minor component. The latter has been reported to reduce the efficiency of major component to trap the male moths. We studied the electrophysiological and behavioral response of male C. partellus moths to Z11-16:Ald, Z11-16OH, their E-isomers (E)-11-hexadecenal and (E)-11-hexadecen-1-ol, and blends. Electroantennogram (EAG) studies revealed that male C. partellus antennae elicited significantly greater responses to both (Z)-11-hexadecenal and (Z)-11-hexadecenol compared to their respective E-isomers. Behavioral response studies through wind tunnel and cage bioassay showed that blends of Z11-16:Ald and Z11-16OH in the proportion of 100:100 and 100:95 elicited significantly higher responses from male moths. The attractiveness of these pheromone components and blends in field also revealed that traps baited with 100:100 proportion was most effective. Our studies clearly showed that the minor alcohol component Z11-16OH is important for enhancing attractiveness of the pheromone and provides a more effective blend for monitoring of this pest.