Combined use of herbivore-induced plant volatiles and sex pheromones for mate location in braconid parasitoids

Authors: XU, HAO - Neuchatel University - Switzerland; DESURMONT, GAYLORD - European Biological Control Laboratory (EBCL); DEGEN, THOMAS - Neuchatel University - Switzerland; LAPLANCHE, DIANE - Neuchatel University - Switzerland; HENRYK, LUKA - Agriculture; TURLINGS, TED - Neuchatel University - Switzerland

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2016
Publication Date: 10/7/2016
Citation: Xu, H., Desurmont, G., Degen, T., Laplanche, D., Henryk, L., Turlings, T.C. 2016. Combined use of herbivore-induced plant volatiles and sex pheromones for mate location in braconid parasitoids. Plant Cell and Environment. Vol 39, Pages 1920-1927. DOI: 10.1111/pce.12818.

Interpretive Summary: Biological control is an important economical, environmentally-friendly, sustainable method for managing insect pests of many crops. Parasitoids (insect parasites of insect pests) are an important type of biological control agent. Many parasitoids are known to use pheromones (sex attractants) to locate mates, and plant odors to locate their insect hosts; however the interaction of these two types of odors is not well understood. We conducted laboratory olfactometer experiments to determine which types of odors were attractive to males and females of four different species of parasitoid that attack three pests of cabbage and/or corn. The results show that pheromones and plant odors can be used in combination by parasitoids to locate mates. This research improves our fundamental knowledge of parasitoids and has the potential to improve biological control programs based on their use.

Technical Abstract: Herbivore-induced plant volatiles (HIPVs) are important cues for female parasitic wasps to find hosts. Here, we investigated the possibility that HIPVs may also serve parasitoids as cues to locate mates. To test this, the odor preferences of four braconid wasps – the gregarious parasitoid Cotesia glomerata (L.) and the solitary parasitoids Cotesia marginiventris (Cresson), Microplitis rufiventris Kokujev and Microplitis mediator (Haliday) – were studied in olfactometers. Each species showed attraction to pheromones but in somewhat different ways. Two male Cotesia species were attracted to female virgins, whereas female M. rufiventris were attracted to male virgins. Male and female M. mediator exhibited attraction to both sexes. Importantly, female and male wasps of all four species were strongly attracted by HIPVs, independent of mating status. In most cases, male wasps were also attracted to intact plants. The wasps preferred the combination of HIPVs and pheromones over plant odors alone, except M. mediator, which appears to mainly use HIPVs for mate location. We discuss the ecological contexts in which the combined use of pheromones and HIPVs by parasitoids can be expected. To our knowledge, this is the first study to show that braconid parasitoids use HIPVs and pheromones in combination to locate mates.