Outbreak of tree-killing, allergy-inducing moths prompts warnings from B.C. government

An infestation of insects that have the ability to quickly kill healthy Douglas fir trees is on the move in British Columbia and the Ministry of Forests says it has now been found further north than ever before.

A statement from the ministry Tuesday said an infestation of tussock moth has been found in trees in the western Cariboo, just south of the community of Alkali Lake.

The pest is usually found in more southern parts of the province, such as Kamloops and the Okanagan. They can kill a large Douglas fir in just one to two years during a severe infestation, according to the ministry.

Tussock moth caterpillars feed on the needles of the Douglas fir, stripping limbs, which appear scorched as they die. Trees weakened by the moth are more susceptible to beetle attacks.

Hairs on the moth caterpillars can also pose a human health risk because the ministry said the hairs can cause allergic reactions in about 20 per cent of people, producing rashes, watery eyes and sneezing.

In an effort to slow the spread of the moth, the ministry said firewood should not be taken from the Wycotte Flat area south of Alkali Lake.

"Tree limbs are particularly infectious, as they may contain eggs,'' the ministry statement said.

The caterpillars, which can be recognized by two long, black tufts on each side of their head and another at the rear, hatch in late spring and develop into moths from late July to early September.

Female moths lay approximately 200 eggs each, which hatch the following spring. The ministry said outbreaks typically last two to four years.

Ministry officials are assessing the affected area and the statement said a treatment plan will begin when the caterpillars re-emerge next spring.