MCH (3-methylcyclohex-2-en-1-one) has long been known as a spruce beetle repellent but few studies have demonstrated its efficacy to protect live trees. A novel high-release device, along with novel repellents, have shown improved efficacy as spruce protectants. The spruce beetle is the most significant mortality agent of spruce in western North America. Management options are limited but an effective semiochemical repellent (a pheromone or other chemical that conveys a signal from one organism to another, which modifies the behavior or the receiving organism) could be economically and environmentally advantageous, compared to insecticide applications, for protection single trees and small stands. MCH is a beetle-produced pheromone that acts as a “no vacancy” signal to other beetles. Forest Service scientists tested MCH and a blend of compounds found in the non-host maple (Acer) kairomone blend (AKB) for their ability to repel spruce beetle from attacking individual trees and groups of trees in an area. The tests were conducted in Utah and New Mexico. They found that the probability of spruce beetle attack in the MCH-treated areas was about one-half of that in the not-treated areas. When they tested compounds to protect individual trees, 75 percent of trees that were baited, but had no MCH or AKB, were mass-attacked. In contrast, about one-third of the trees that were baited and also had either MCH or AKB spruce were mass-attacked, and no trees with a combination of MCH and AKB were mass-attacked. These results suggest that when MCH is applied alone, it is a marginal area and single tree protectant against spruce beetle. When MCH is applied with other non-host repellents, there is a significant increase in the number of trees protected from spruce beetle attacks. They continue to test both MCH and AKB for their use in protecting individual trees and areas from spruce beetle. In summary, the scientists found: High-release rate MCH devices can reduce spruce infestation rates by spruce beetle. Efficacy can be improved by adding other spruce beetle repellents. And, further testing is ongoing but results to date suggest that an effective, economical repellent will soon be available.