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This insect, native to North America, is regarded as a defoliator of primary importance. It is found from the Atlantic coast to as far west as Alberta (with a western species present in British Columbia). In eastern provinces, the main host of this insect is balsam fir, and in western provinces, it feeds primarily on hemlock. In the east, during severe and prolonged outbreaks occurring from southern Ontario to Newfoundland, the hemlock looper will feed on many other conifers and even hardwoods (such as birch, maple, and poplar). Since the first outbreak in 1912, this insect has been a particularly significant pest in Newfoundland with waves of 3- to 6-year epidemics occurring every 10–15 years.

Damage by hemlock looper is found mainly in pure stands of balsam fir or those mixed with white spruce and occasionally black spruce. Defoliation is the predominant damage to the tree as well as growth reduction and mortality of affected parts of the tree. Mortality is usually restricted to mature stands of balsam fir and eastern hemlock.

Points of interest

• one generation per year
• young larvae are positively phototropic and stay on the outside of the crown feeding on new needles
• as larvae mature they become negatively phototropic and seek shaded areas feeding on older needles
• in severe infestations, trees may be stripped of foliage in a single season
• if food is lacking, they may eat one another
• the larvae are considered wasteful feeders because they rarely eat the whole needle
• average of mature larval or full-grown length is 32 mm

References

Martineau, R. 1984. Insects Harmful to Forest Trees. Multiscience Publications Ltd., Montreal, Environment Canada, Canadian Forestry Service, Ottawa, and Supply and Services Canada, Canadian Government Publishing Centre, Ottawa. For. Tech. Rep. 32. 261 p. + x.

Rose, A.H.; Lindquist, O.H. 1994. Insects of Eastern Spruces, Fir and Hemlock. Natural Resources Canada, Canadian Forest Service, Ottawa, and Canada Communication Group—Publishing, Ottawa. Revised edition. 159 p.