The spruce beetle is the most significant mortality agent of spruce in western North America. Management options are limited. An effective non-insecticide ‘semiochemical’ repellent could be economically and environmentally advantageous for protection of single high-value trees and small stands in campgrounds and urban areas. Semiochemicals are substances released by trees (kairomones) and insects (pheromones) that convey signals among organisms.
MCH (3-methylcyclohex-2-en-1-one) is a spruce beetle-produced pheromone that acts as a “no vacancy” signal to other beetles. Tree species that are not hosts of the spruce beetle, for example maple (Acer), produce kairomones (volatile terpene alcohols) that may send ‘not your type’ signals to spruce beetles. When the two are combined, powerful things can happen. In a collaborative effort between Rocky Mountain Research Station and Forest Health Protection, MCH and a blend of compounds found in the non-host Acer (AKB) was tested for their ability to repel spruce beetle from attacking individual trees and groups of trees in an area. MCH-AKB in pouch release devices were found to be superior to MCH alone for protection of individual trees and groups of trees from spruce beetle attacks in Utah, Colorado, Wyoming, and New Mexico. Protection was enhanced on trees up to 10 m from the repellant location.
Although MCH is currently EPA-registered for use against spruce beetles, EPA registration is required for AKB before it can be used in non-research situations. We envision deployment of pouches in areas with high-value spruce including campgrounds, ski areas, and the wildland-urban interface.