Minor Components Play an Important Role in Interspecific Recognition of Insects: A Basis to Pheromone Based Electronic Monitoring Tools for Rice Pests

Several lepidopteran species share the same pheromone blend consisting of (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-9-hexadecenal (Z9-16:Ald) at different ratios and active doses. In rice pest Chilo suppressalis, (Z)-11-hexadecenol, (Z11-16:OH) and octadecanal (18:Ald) were identified as minor components in the pheromone gland of female moths, and these components were previously not considered as part of the sex pheromone of C. suppressalis. Z11-16:Ald, Z9-16:Ald and (Z)-13-octadecenal (Z13-18:Ald) frequently trapped other lepidopteran species, such as rice pests Scirpophaga incertulas and Mythimna separate, corn and vegetable pests Helicoverpa armigera in the field, suggesting a lack of specificity in the pheromone blend. Our data showed that the minor component Z11-16:OH did not have a synergistic effect on the attractiveness of the blend to C. suppressalis; however, pheromone mixtures containing Z11-16:OH failed in trapping male H. armigera moths. We confirmed the identity and specificity of the C. suppressalis sex pheromone and demonstrated that Z11-16:OH plays a key role in the reproductive isolation of C. suppressalis, M. separata, and H. armigera moths, and a similar role of Z9-18:Ald in that of S. incertulas and C. suppressalis. This phenomenon could be more widely applicable to interspecific interactions in the pheromone communication between insects, which is crucial to developing the electronic automatic counting device for automatically monitoring the pest population by pheromone trapping based on its species specificity.