Reevaluation of the sex pheromone of the lesser date moth, Batrachedra amydraula, using autosampling SPME-GC/MS and field bioassays

Abstract

In a previous study of the sex pheromone of the lesser date moth, Batrachedra amydraula, using laboratory females, (Z4,Z7)-4,7-decadien-1-yl acetate, Z4-decen-1-yl acetate, Z5-decen-1-yl acetate and decyl acetate were identified by sequential SPME-GC/MS analysis. Traces of Z5-decen-1-ol were detected only in airborne collections. Concomitant field tests and re-evaluation of the composition of the sex pheromone of B. amydraula with feral female moths, using an improved sequential SPME-GC/MS procedure revealed a complex mixture of candidate pheromonal compounds. The same unsaturated acetates and the corresponding alcohols: (Z4,Z7)-4,7-decadien-1-ol, Z4-decen-1-ol, Z5-decen-1-ol were positively identified. In addition, the corresponding aldehydes, octanol and octyl acetate were also detected. All compounds were found to be released in a circadian rhythm, in a narrow time window of 2 h, approximately 1 h before sunrise. Comprehensive field bioassays indicated that the optimal attractive blend is a three-component mixture of (Z4,Z7)-4,7-decadien-1-yl acetate, Z5-decen-1-yl acetate and Z5-decen-1-ol in a ratio of 1:2:2. This blend gave about fivefold higher trap catch of B. amydraula males as compared to the previously published binary blend of (Z4,Z7)-4,7-decadien-1-yl acetate and Z5-decen-1-yl acetate in a ratio of 1:2. The alcohol Z5-decen-1-ol is an essential synergistic component of the sex pheromone of B. amydraula. All other identified compounds are inert, being neither synergists nor inhibitors of the pheromone. The optimal pheromone blend will be a useful tool in monitoring and control of B. amydraula, which is a serious pest of date plantations throughout the Middle East and northern Africa.