Female sex pheromone blends and male response of the legume pod borer, Maruca vitrata (Lepidoptera: Crambidae), in two populations of mainland China.

The legume pod borer, Maruca vitrata (Lepidoptera: Crambidae; syn. M. testulalis), is a serious pantropical insect pest of grain legumes. Comparative studies of M. vitrata female sex pheromone components in two different geographic populations in China, Wuhan and Huazhou, confirmed that (E,E)-10,12-hexadecadienal (E10,E12-16:Ald) and (E)-10-hexadecenal (E10-16:Ald) were present in variable ratios in all pheromone gland extracts of both populations. (E,E)-10,12-hexadecadienol (E10,E12-16:OH) was always detected in minor amounts using polar DB-WAX columns, but was never detected using medium-polar DB-17 columns for the two populations. E10-16:OH was not found in any of the M. vitrata sex pheromone gland extracts. The average ratios of E10-16:Ald, E10,E12-16:Ald, and E10,E12-16:OH in the pheromone gland extracts of populations from Wuhan and Huazhou were 79.5:100:12.1 and 10.3:100:0.7, respectively. Electrophysiological testing suggested that E10,E12-16:Ald elicited the highest male electroantennography (EAG) response, followed by E10,E12-16:OH and E10-16:Ald. Field-trapping tests with single synthetic sex pheromone lures showed that E10,E12-16:OH alone could not attract males, whereas E10,E12-16:Ald or E10-16:Ald alone attracted few males. Wuhan and Huazhou males were most attracted by lures containing E10-16:Ald + E10,E12-16:Ald + E10,E12-16:OH in doses of (80 + 100 + 10) microg and (10 + 100 + 10) microg, respectively, per vial. Males could discriminate between the blends that were most attractive to their own geographic population and those that were most attractive to the reference population. Our findings suggest that geographic variation exists in the sex pheromone system of M. vitrata in China. The results are discussed with regard to the mechanisms underlying the sex pheromone variation.