Pheromone antagonism in lepidopteran maize pests

Abstract: Coinciding with the deployment of Bt maize in the study area, but not necessarily dueto it, populations of corn borers have decreased in the last few years, while the incidence of otheraerial Lepidoptera, such as Mythimna unipuncta and Helicoverpa armigera, seems to haveincreased. In previous papers we showed that Z11-16 Ald, a Sesamia nonagrioides component,inhibits pheromone perception by Ostrinia nubilalis males, whereas the two components ofO. nubilalis pheromone inhibit perception by S. nonagrioides males in EAG, wind tunnel andfield trials. We have also recorded the inhibitory effect of the aldehyde on M. unipunctapheromone perception in wind tunnel and field trap trials. In the current paper we present thestudy on how H. armigera respond to this inhibitory system. Effects of different pheromonecomponents of S. nonagrioides, M. unipuncta and O. nubilalis on the behaviour of H. armigeramales in the wind tunnel are reported. Maximum response in upwind flight and source contactwas recorded with the mixture of the H. armigera major (also present in S. nonagrioidespheromone) and minor components [Z11-16:Ald and Z9-16:Ald respectively], whereas noresponse to the O. nubilalis pheromone components was observed. Addition of Z11-16:OH (forsome authors a component of H. armigera pheromone) significantly reduced response in thisspecies, so it is thought that additional doses should be tested.