Field trapping of the invasive brown marmorated stink bug, Halyomorpha halys, with geometric isomers of methyl 2,4,6-decatrienoate

The brown marmorated stink bug, Halyomorpha halys (Stål), is a polyphagous pest indigenous to northeastern Asia where it damages various trees, vegetables, and leguminous crops. The bug was recently introduced into the U.S. and could potentially become a pest. In its native range, H. halys was reportedly attracted to the aggregation pheromone of the brown-winged green bug, Plautia stali, methyl (2 E,4 E,6 Z)-decatrienoate. We also observed that traps baited with this compound are attractive to H. halys. We additionally found that methyl (2 E,4 E,6 Z)-decatrienoate (as well as other isomeric methyl 2,4,6-decatrienoates) exposed to daylight in solutions and/or on dispensers used for field trapping can readily isomerize to form complex mixtures of isomers, thus causing a concern about lure stability and longevity. However, our studies demonstrated that preventing isomerization of methyl (2 E,4 E,6 Z)-decatrienoate in dispensers was not essential for field trapping of H. halys males, females, and nymphs. We also present evidence that traps baited with methyl (2 Z,4 E,6 Z)-decatrienoate and methyl (2 E,4 Z,6 Z)-decatrienoate (pheromone of Thyanta spp. pentatomids), as well as the mixtures of geometric isomers, attract H. halys. The ZEZ isomer, unknown in nature, as well as the EEZ isomer, elicited electrophysiological responses from antennae of H. halys males. The field data suggest that the presence of the EEZ but not ZEZ isomer in the lure is essential for attraction of H. halys, and that other isomers are not antagonistic and may even be needed for maximum attraction. Because the pheromone of H. halys is unknown at present, lures containing methyl (2 E,4 E,6 Z)-decatrienoate without protection from daylight are suitable for monitoring populations of H. halys late in the season.