Detecting emerald ash borers (Agrilus planipennis) using branch traps baited with 3D-printed beetle decoys

Small visual-decoy-baited traps for the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), have been researched as an alternative to current technologies, but have relied on real beetles rather than synthetic materials. We hypothesized that visual decoys created by three-dimensional (3D) printing can provide such a substitute. Branch traps displaying decoys consisting of real EAB females or 3D-printed decoys were compared to controls without decoys. Traps of the three varieties were placed on neighboring branches along with one (Z)-3-hexen-1-ol lure per tree and checked daily. Both real and 3D-printed decoys similarly increased EAB trap captures compared to controls. The numbers of both sexes were higher on the decoy-baited traps, but the increase in male captures was more pronounced. Males were also ensnared closer to the decoys than females. Daily trap-capture patterns showed sparse activity of EAB adults before June 18, 2013 followed by a peak in captures of both males and females until June 28, 2013. Beginning at approximately July 1, 2013, there was a second peak of EAB captures, which consisted almost entirely of males caught on the decoy-baited traps. The native ash borer Agrilus subcinctus was found earlier in the season and was also significantly attracted to both the real EABs and the 3D-printed decoys compared with control traps. Four purple prism traps were also deployed concurrently and captures tallied on three different days within the season. The results demonstrate efficacy of a small, inexpensive, and fully synthetic decoy-based branch trap system for EAB.