Disruption of moth mating behaviour by olfactory and auditory cues

Abstract: The impact of olfactory and auditory cues on the mating behaviour in two species of moths, Agrotis segetum (Noctuidae) and Plodia interpunctella (Pyralidae), was investigated to evaluate their potential use in integrated pest management. The flight behaviour of male A. segetum under natural and pheromone-based mating disruption conditions was monitored by harmonic radar. Individual males were equipped with a radar transponder, released and tracked in the field. Although the trap catch of males and the frequency of fertilised females were reduced by 79% and 62%, respectively, in pheromone-treated vs untreated plots, no drastic differences in flight behaviour between plots could be detected. The analysis was constrained by the fragmentation of tracks due to radar shadow. The potential to use sex pheromones for suppression of mating of P. interpunctella was evaluated. Mating was reduced by up to 93% in pheromone-treated tents compared to control tents, but no difference in mating disruption effect was observed when a four-component blend and the major component, Z9,E12-14:OAc, alone were used as disruptants or when the population density was altered. The risk of resistance evolution to pheromone-based mating disruption was studied by combined heritability and selection experiments. The heritability of the pheromone blend of P. interpunctella, measured as the ratio between Z9,E12-14:OAc and Z9,E12-14:OH, was estimated to 0.65, indicating a potential for a change of the trait via selection. However, no increase in mating frequency or change in pheromone blend composition compared to control moths was observed after three generations of selection in three separate lines, which indicates a limited potential for resistance evolution to the pheromone treatment. Flight tunnel studies were performed to study how ultrasound-triggered evasive behaviours of moths to attacking bats are influenced by sex pheromone stimulation. Male A. segetum and P. interpunctella showed less evasive reactions to ultrasound when flying towards highly adaptive sex pheromone sources compared to sources of lower adaptive value, indicating a trade-off between mate finding and predator avoidance. The quantitative reduction in evasive reaction to ultrasound exposure was estimated for P. interpunctella. At the frequency of best hearing (50 kHz), the threshold for flight stop of tethered males not stimulated with sex pheromone was at 70 dB SPL, whereas this threshold was increased to 95 dB SPL in free flying males stimulated with sex pheromone. Finally, the effect of high frequency sound on parameters involved in the odour-mediated mating behaviour of P. interpunctella was studied to evaluate the use of sound technology for population control. All phases in the reproduction process (female calling, male response to sex pheromone, female response to olfactory oviposition cues, mating activity) were affected by ultrasound stimulation.