Western hemlock looper management

The Southern Interior Area manages western hemlock looper damage by monitoring populations in susceptible stands. When significant damage is predicted, plans are developed to reduce defoliation through targeted aerial spraying using the biological insecticide Bacillus thruringiensis var. kurstaki (Btk).  

On this page

• Predictive sampling techniques
• Long-term strategies
• Short-term strategies

Predictive sampling techniques

Egg sampling happens in the fall when defoliation has been noticed, or when an outbreak is anticipated. The egg samples predict levels of defoliation the following summer.

Long-term strategies

A stand that is well-spaced, even-aged and thrifty is less likely to be impacted by western hemlock looper defoliation.

Mixed-species stands with the following characteristics are less susceptible to damage:

• Less than 50% western hemlock
• Few cedar-hemlock mixes
• Non-host species 

Stand-tending treatments such as spacing and fertilization will help maintain a healthy, resilient stand.

Short-term strategies

The recommended short-term strategy is:

• Identify high-hazard stands containing the highest frequency of infestations, and monitor those areas in years before the next outbreak is expected

In eastern Canada, Bacillus thruringiensis var. kurstaki (Btk) has been sprayed on outbreaks. In 1993 B.C. tested two formulations of Btk. The formulations were effective and the information was used to obtain registrations for use against the western hemlock looper.

Some chemical insecticides are also registered for use in B.C. but have not been applied operationally to protect Crown forests.