Western hemlock looper

Last updated on January 29, 2024

This insect periodically reaches outbreak levels, causing severe damage to forests in both Interior and coastal stands in British Columbia.

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Description

Although outbreaks are short-lived (one to three years), the wide range of host species and ages, and extensive feeding on foliage of any age, results in high levels of mortality in heavily defoliated conifers. Loss of valuable timber, increased fire danger risks, and loss of important wildlife habitat can result from hemlock looper outbreaks. 

Host tree species

The western hemlock looper is a native defoliator of western hemlock, western redcedar, interior spruce and Douglas-fir.

Life cycle

Larvae hatch in the spring and feed lightly during May, June and early July, then heavily from the middle of July to October.

Damage symptoms

Damage from western hemlock looper is generally visible in late summer as larvae develop and feed on susceptible host tree species. Looper larvae are known as wasteful feeders because they eat part of all of both old and new foliage.

Defoliation from looper results in browning foliage and fallen needles at the base of the host trees.

Identification images

 

Larvae

Looper on a leaf

 

Moth

Moth perched on a pine twig

 

Damaged trees

aerial view of damaged trees

 

 

Fast facts
Western hemlock looper on a leaf

Type: native defoliator

Targets: western hemlock, western redcedar, Interior spruce and Douglas-fir

Outbreak frequency: every 11 years (interior) and 20-plus years (coast)

Outbreak duration: usually about three years

Damage: in heavy infestations, trees may be stripped in a single season