Douglas-Fir Tussock Moth

April 24, 2023

closeup of a pale tussock moth


Douglas-Fir Tussock Moth, Orgyia pseudotsugata, is a moth that infests true firs, Douglas-fir, and spruces. Its preferred hosts are Douglas-Firs. Although the moth is a native species, with the right environment and circumstances outbreaks can be seen in Colorado forests. 

Caterpillars can be seen after they begin hatching in late-May. The caterpillars often spread to uninfested trees by being blown in the wind from their eggs after hatching. After maturing they pupate and emerge as adult moths in late-July to August. The adults then mate and lay their eggs. 



Tussock moth caterpillars defoliate their host tree by feeding on current year needles after they hatch, they then will feed on older needles as fresh needles are exhausted. Defoliation can cause the tree to become stressed which can leave it open to attack from borer beetles. Repeated stress from tussock moths and attacks from beetles can cause death of the tree. 



Egg masses and cocoons can be seen on trees that have a tussock moth presence. Female moths cannot fly so they will often be seen close to their cocoons. Defoliation will also be apparent after bud break as the eggs hatch and the larvae begin to feed. Defoliation usually begins at the top of trees and progresses downwards. 



Tussock moth populations normally do not require control due to natural controls such as viruses or predators. However in times of outbreak chemical control may be required. 

Pesticide sprays can be used to control the population by killing their caterpillars before they can cause too much damage to the tree. They, however, are not the most environmentally friendly and can cause harm to other wildlife including bees and birds. 

Trunk injections have also proven to be an effective method of control, but their cost limits most treatments to select trees of value rather than groups of multiple trees.



If you believe your trees have been infested, contact a local tree service company as soon as possible. Splintered Forest is a leading fire mitigation and tree service provider serving the mountain communities. We are committed to delivering the best service in the industry. Our skilled crew includes ISA Certified Arborists, Plant Health Care technicians, experienced tree climbers and expert tree fellers who can expertly assess and address your Douglas-Fir Tussock Moth problem. Contact us today to schedule your free, no obligation estimate.