Molecular and pheromone studies of pecan nut casebearer

The pecan nut casebearer Acrobasis nuxvorella Nuenzig (Lepidoptera: Pyralidae) is the most damaging insect of pecan Carya illinoinensis (Wang) K. Koch (Fagales: Juglandaceae). A pheromone monitoring program for A. nuxvorella has been developed to assist growers in the timing of insecticide applications. The discovery that there are at least two pheromone types produced by A. nuxvorella has led to complications in the implementation of a pheromone monitoring program for this insect. One pheromone is attractive to male moths in the US, while the other pheromone is attractive to male moths in the US and Mexico. The blend that is only attractive to A. nuxvorella in the US is comprised of an aldehyde, while the other blend is comprised of an aldehyde and an acetate. Because most male Lepidopterans respond only to a conspecific chemical signal, it was suspected that there were two strains of A. nuxvorella. In order to ascertain the relationship between the two postulated strains of A. nuxvorella, AFLP markers were developed and analyzed. Results of genetic analyses show that the genetic differentiation between these insects is not explained by pheromone type. This information is further supported by a pheromone assay. In this assay, a large proportion of male moths from the US chose both pheromone types during different tests, and it is suspected that male moths from Mexico will only respond to the aldehyde and acetate blend.