Smelling the Wood from the Trees: Non-Linear Parasitoid Responses to Volatile Attractants Produced by Wild and Cultivated Cabbage

Abstract

Despite a large number of studies on herbivore-induced plant volatiles (HIPVs), little is known about which specific compounds are used by natural enemies to locate prey- or host- infested plants. In addition, the role of HIPVs in attracting natural enemies has been restricted largely to agricultural systems. Differences in volatile blends emitted by cultivars and plants that originate from wild populations may be attributed to potentially contrasting selection regimes: natural selection among the wild types and artificial selection among cultivars. A more realistic understanding of these interactions in a broader ecological and evolutionary framework should include studies that involve insect herbivores, parasitoids, and wild plants on which they naturally interact in the field. We compared the attractiveness of HIPVs emitted by wild and cultivated cabbage to the parasitoid Cotesia rubecula, and determined the chemical composition of the HIPV blends to elucidate which compounds are involved in parasitoid attraction. Wild and cultivated cabbage differed significantly in their volatile emissions. Cotesia rubecula was differentially attracted to the wild cabbage populations and preferred wild over cultivated cabbage. Isothiocyanates, which were only emitted by the wild cabbages, may be the key components that explain the preference for wild over cultivated cabbage, whereas terpenes may be important for the differential attraction among the wild populations. Volatile analysis revealed that parasitoid attraction cannot be explained by simple linear relationships. Our results suggest that unraveling which compound(s) are innately attractive to parasitoids of cabbage pests should include wild Brassicaceae.

Behavioural and physiological responses to prey-related cues reflect higher competitiveness of invasive vs. native ladybirds

“…Plants may indirectly affect the natural enemy community exploiting their herbivorous pests by mediating multitrophic interactions 57 . In this respect, the possibility of using plant volatiles to manipulate predator behaviour is promising when the purpose is to enhance the biological control of crop pests 58 or control populations of invasive predators 46 .…”

An ecogenomic analysis of herbivore‐induced plant volatiles in Brassica juncea

“…; Gols et al . ). Many laboratory studies have demonstrated that HIPVs make plants more attractive to host‐seeking natural enemies (van Poecke et al .…”

Two Volatile Organic Compounds Trigger Plant Self-Defense against a Bacterial Pathogen and a Sucking Insect in Cucumber under Open Field Conditions

“…Insect behavior studies show that 3-pentanol plays a critical role as a pheromone in the sexual communication of M. mutates [21]. In addition, 3-pentanol is produced by wild Brassica oleracea plants in response to infestation by the caterpillars Pieris rapae and Plutella xylostella [23,24]. Plants were recently shown to produce 3-pentanol as an olfactory stimulus.…”