Douglas-Fir Tussock Moth

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The Douglas-Fir Tussock Moth is the adult stage of insects that start off as caterpillars. They are defoliators for many trees, and it’s important to deal with an infestation before it gets too bad.

The larvae the moths produce are also defoliators. They are more of a problem for plants with needles and small leaves as they chew on them before metamorphosis.

The Life Cycle of a Douglas-Fir Tussock Moth

The Douglas-Fir Tussock Moth goes through one generation a year. During the winter, the moths will lair their eggs. Those eggs hatch in late May, when it is much warmer out. The larvae then migrate to the top of the trees before being dispersed by thew wind. They don’t remain with the infested tree.

Larvae will chew on plants and then cocoon. They emerge as adults from late July to the middle of August.

The males will have rust-colored forewings and gray-brown back wings. Females are wingless.

The Type of Damage Done to Trees

The Douglas-Fir Tussock Moth will spend their time on the Colorado blue spruce, the white fir, the Engelmann spruce, and the Douglas-fir, where it gets its name from.
They defoliate the trees from the top down, and you’ll often see that the tops of the trees have died due to them. If there are repeated attacks, the trees can die. They are also made susceptible to the bark beetles due to the damage.

Handling the Douglas-Fir Tussock Moth

There are a few methods to deal with infestations. If you’re looking for something natural, you can introduce parasitic wasps, spiders, and tachinid flies to the area. Another option is to bring in a virus that causes wilt disease.

Most people will go for chemical options. Insecticides are popular, but you’ll need to concentrate on the tops of the trees as this is where the moths prefer to start. You can use Bt, carbaryl, acephate, pyrethrins, pyrethroids, and Spinosad treatments.

Look out for signs of a larval stage infestation. If you can deal with this, you can minimise the moths becoming the issue.

SprayTech is tree spraying and weed control company. We work in Douglas county and surrounding areas.