This Evergreen Tree Pest Update discusses the Tussock Moth and Pine Sawfly. These insects devastate evergreens in Colorado. Denver homeowners need to get informed about these tree pests. Homeowners who see clusters of larvae on their Pine, Spruce or Fir trees, click here to fill out a service request form to make an appointment with a Ross Tree Plant Health Care Specialist.

Douglas Fir Tussock

top down tussock damage      tussock moth larvae

The Douglas Fir Tussock moth is native to Colorado. Their pretty, fuzzy caterpillars devastate Fir and Spruce trees. Outbreaks tend to be abrupt and occur in ten-year cycles. During epidemics, the Tussock larvae defoliate trees. They start munching at the top and work their way down. Annual attacks on individual trees will eventually kill them.

The adult Douglas Fir Tussock moths are bland in appearance. The female moths cannot fly. After their eggs hatch in late May or early June, these highly mobile caterpillars spread out attacking adjacent trees. Proper tree thinning is an excellent control option promoting healthy growth which helps trees withstand the moth and its larvae. The best time to treat is in early spring. Check out the Colorado State Extension Service bulletin on the Douglas Fir Tussock moth.

Pine Sawfly

pine sawfly damage    conifer sawfly

The Pine Sawfly made its presence known in Colorado by defoliating Ponderosa Pine forests in Elbert County. The adult Sawfly is a stout stingless wasp and flew north into the Denver Metro Area. Pine Sawfly infestations are hard to miss with large populations of larvae feeding on pine needles. Click here to read the Denver Post’s article about the Sawfly attack on Ponderosa Pines along the Front Range.

Evergreens are an important component of the Denver urban forest. Please use this Evergreen Tree Pest Update to identify the Tussock Moth and Pine Sawfly and their larvae. Ross Tree is at your service if these tree pests are found in your tree landscape.