The mountain pine beetle (Dendroctonus ponderosae) has not been detected in Michigan but is on the states watch list. This beetle has been found in western North America. It can infest most of our pine tree species found in Michigan. This beetle is typically ¼ inch and are black to dark brown. It can be hard to see the insect so looking for characteristic damage can be useful. The needles may turn red or yellow in the summer when the tree is infested. Other evidence are blotches of pitch that can be pink, white, or brown. Red frass in tree crevasse is also a sign of their presence.
Have you seen this species? Report it to us or on the MISIN website or smartphone app! Please include a photo to help with ID verification.
Environmental Impacts
Mountain pine beetle is native to western Canada and is spreading to other parts of North America. Climate change has resulted in warmer winters which allows more of the pine beetles to survive. Previously harsh winters would kill most adults and larvae and reduce the population size. Adults and larvae eat the vascular tissue (phloem) of the tree which greatly weakens it. This combined with adults spreading blue stain (Grosamannia clavigerain) fungal spores can kill the tree completely. Due to warming climate, this species has the ability to harm or kill large stands of pines outside of its native region.
Treatments
Preventative herbicide treatment is the only option for protecting pines from mountain pine beetles. Insecticide can be sprayed onto the bark in early June. It should be sprayed from the ground and up the trunk 35 feet or where the trunk is 5 inches or less in diameter, which ever occurs first. It is important to apply enough to fully wet the bark. Insecticide kills the adult beetles once they come into contact with it.