Eastern spruce budworm

Choristoneura fumiferana 

The eastern spruce budworm is a tortricid moth often called the spruce budworm outside of British Columbia. It's a major defoliator in boreal forests in eastern Canada.

On this page:

Description

These budworms are mostly found in the Fort Nelson Natural Resource District but have also been found in the Fort St. John Timber Supply Area.

The spruce budworm has been associated with the term "Spruce Decline Syndrome". This term is being used to describe those stands that have entered a general state of decline following the collapse of the last budworm outbreak in 1995.

The spruce budworm typically has a 20-year outbreak cycle.

Host tree species

The main host of the eastern spruce budworm in the Fort Nelson Natural Resource District is white spruce.

Life cycle

The eastern spruce budworm disperses locally after hatching. Long-range migration is possible when adults move to avoid harsh weather conditions.

The eastern spruce budworm has a one-year life cycle. Most defoliation occurs in spring during larval development before pupation and the adult moths disperse.

Damage symptoms

The larval stage defoliates host trees and causes visible damage and tree mortality. When trees are stressed they are more likely to die. Defoliated trees appear brownish-red and scorched on the upper crown and branches. Larvae eats the current years needles and buds.

Repeated budworm defoliation causes tree mortality over large areas, reduction of growth rates and reduced lumber quality. Sustained attack results in complete defoliation in four to five years.

Identification images

 

Egg

egg to scale on a needle

egg on a twig with a blue background

 

Young larvae 

larvae crawling on a twig

Mature larvae

Mature larvae eating

 

Several pupae, showing size variation and colourfinger pointing at a branch with a pupae

 

Moth crawling on a twig

 

Damage by young larvae

damaged tips of a twig

Damaged branch

damaged spruce branch

Aerial damage

damaged forest from the air