Chemical ecology of two co-occurring Lygus species on shared host plants

Generalist and Hemipteran insects are both understudied in terms of their chemical ecology even though many Hemipterans are major insect pests in agricultural ecosystems. A greater understanding of chemical cues that mediate interactions among host plants, Hemipterans, and their natural enemies would benefit biological control efforts and contribute to a basic understanding of plant-insect interactions. Here we took a comparative approach to examine interactions among two species of generalist Lygus bugs (Hemiptera: Miridae), and their most commonly utilized agricultural and weedy host plants. One species, Lygus lineolaris, has a broad range throughout the eastern U.S. and is a serious agricultural pest on alfalfa, cotton, and many fruit crops. The second species, Lygus rubrosignatus, co-occurs with L. lineolaris on many hosts in the northeast, but is rarer and is not considered a target of pest control measures. However, both species are attacked by parasitoid wasps in the genus Peristenus that were introduced from Europe and the Mediterranean to control L. lineolaris in the U.S. Our experiments demonstrate that both Lygus lineolaris and Lygus rubrosignatus induce characteristic volatile blends when feeding on different host plant species, including alfalfa (Medicago sativa), sweet clover (Melilotus officinalis), fleabane (Erigeron sp.), and cotton (Gossypium hirsutum), and that differences among these blends must be negotiated by Peristenus wasps when foraging for hosts. The implications of our results are discussed in relation to the effectiveness and impact of Lygus lineolaris biocontrol programs that utilize Peristenus wasps.