Interactions between Lygus bugs and Erigeron annuus: applications toward a trap crop system for the tarnished plant bug

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 control efforts. A common field edge weed, Erigeron annuus, is remarkably attractive to the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), which is a highly damaging pest on multiple crops. These attractive cues function over long distances and result in both attraction and arrestment of L. lineolaris. However, the mechanism of this attraction is currently unknown. Understanding the mechanisms by which E. annuus attracts and arrests L. lineolaris would facilitate use of Erigeron to direct the movements of Lygus in the field. To understand how E. annuus is attractive, we explored the blend of volatile organic compounds emitted by the plants with and without the presence of Lygus bugs. Volatile collections from E. annuus demonstrate that this species produces a highly complex volatile blend consisting of over 60 distinct compounds at amounts far greater than co-occurring crop hosts of L. lineolaris. Furthermore, when fed upon by Lygus, novel compounds are induced and constitutive compounds up-regulated. These results, along with behavioral observations, indicate that L. lineolaris will preferentially visit and aggregate on this weedy host. Erigeron may therefore be useful to concentrate Lygus into a small area – adjacent to or separate from crops – that could then be subject to application of chemical or biological controls.