Efficacy of a bead formulation of MCH for protecting live Douglas-fir from infestation by Dendroctonus pseudotsugae (Coleoptera: Curculionidae)

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), has been used operationally in western North America to protect high-risk, high-valued trees during outbreaks since the spring of 2000. The most commonly used formulation of MCH is a bubble capsule manufactured by several different companies. Bubble capsules are made of 2 layers of plastic film that breakdown very slowly under natural conditions requiring resource managers to remove them after treatment in some situations. In this study, a small bead formulation of MCH (Hercon Bio-Beads MCH, patent pending No. 18/521,155) made of biodegradable ingredients was tested. A preliminary study in 2022 demonstrated that Hercon Bio-Beads MCH were efficacious. Due to constraints with accessibility, the 2022 study used 0.04-ha circular plots located 20 to 30 m from each other. The plots were smaller and located closer to each other than is preferred in this type of study. In 2023, a study was conducted using 0.4-ha circular plots that were well spaced and not a single tree was infested on the Hercon Bio-Beads MCH-treated plots. In contrast, 13.8% of potential host trees were fully infested on control plots and 18.6% were either partially or fully infested. The treatment differences in infested trees were not only statistically significant, but also operationally significant. Collectively, the results of these 2 studies demonstrate that Hercon Bio-Beads MCH are highly effective for protecting live trees and are a viable alternative to current commercially available formulations of MCH.