Plant Volatiles Modulate Seasonal Dynamics between Hosts of the Polyphagous Mirid Bug Apolygus lucorum.

Plant-derived volatiles play a significant role in host selection of phytophagous insects, but their role in seasonal host shifts remain unclear. The polyphagous mirid bug Apolygus lucorum displays marked seasonal host alternation. During summer, volatiles from flowering plants play a key role in A. lucorum foraging. Though A. lucorum adults deposit overwintering eggs on jujube (Ziziphus jujuba) and grape (Vitis vinifera) during autumn, it is unclear whether plant volatiles equally mediate this host selection behavior. During 2015 and 2016, we found that population densities of A. lucorum adults on cotton (Gossypium hirsutum) during August were higher than those in September, whereas the opposite pattern was observed on fruit trees (i.e., jujube and grape). The dispersal factor of the adult population that dispersed from cotton fields during September was higher than in August, whereas opposite patterns were observed in the neighboring jujube/grape orchard. In Y-tube olfactometer trials, A. lucorum adults preferred cotton plant volatiles over fruit tree odors in August, whereas the opposite patterns were found in September. Three electro-physiologically active volatiles (butyl acrylate, butyl propionate and butyl butyrate) were identified from jujube and grape plants. During September, active volatiles are emitted in considerably greater amounts by jujube and grape than in August, while the amount of volatile emissions in cotton decreases in September. Temporal shifts in plant volatile emission thus may modulate host plant foraging of A. lucorum, and appear to guide its colonization of different host plants. Our findings help understand the role of plant volatiles in the host plant selection and seasonal dynamics of polyphagous herbivores.

Perception of and Behavioral Responses to Host Plant Volatiles for Three Adelphocoris Species.

In China, the genus Adelphocoris (Hemiptera: Miridae) includes three dominant pest species (A. suturalis, A. lineolatus and A. fasciaticollis), which cause great damage to cotton, alfalfa and other crops. In this study, we examined the role of the major volatile organic compounds from plants in host location by these three insects. Gas chromatography-electroantennography and gas chromatography/mass spectrometry analyses identified seven electroantennogram (EAG)-active compounds from 11 host plants. Although the insects responded to all of these compounds in EAG trials, some compounds did not elicit behavioral responses in Y-tube olfactometer bioassays. Adelphocoris suturalis adults showed behavioral responses to four EAG-active compounds, n-butyl ether, butyl acrylate, butyl propionate and butyl butyrate. These four compounds, in addition to p-xylene, were also attractive to A. lineolatus adults. However, A. fasciaticollis adults were attracted only by butyl acrylate, butyl propionate and butyl butyrate. In field trials, A. suturalis and A. fasciaticollis were each attracted to five individual compounds (m-xylene, n-butyl ether, butyl acrylate, butyl butyrate and butyl propionate for A. suturalis and m-xylene, butyl acrylate, butyl butyrate, butyl propionate, and 1,8-cineole for A. fasciaticollis). By contrast, A. lineolatus aduts were attracted to six individual compounds, m-xylene, p-xylene, n-butyl ether, butyl acrylate, butyl butyrate, and butyl propionate. These compounds may be important in host plant location by the Adelphocoris species, and may be useful for developing attractants for adults of these species.