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This imported defoliating insect is a potentially serious pest. Because these insects consume primarily old foliage, even severely defoliated trees could withstand repeated attacks before dying. However, this defoliation also renders the tree susceptible to other insects feeding on the new foliage, for example, jack pine budworm, Choristoneura pinus pinus Free., thereby increasing the risk for tree mortality. The biggest threat from this insect is to the Christmas tree industry as it is a particular pest in Scots pine plantations, although it feeds on many species of pines. This insect has been found in considerable numbers in plantations throughout Ontario, and the threat to natural stands is a major concern.

Points of interest

• one generation per year
• first recorded in Canada in 1939 in Windsor, Ontario
• when larvae finish feeding, they drop to the ground to spin their cocoon
• term "sawfly" is derived from a tiny saw-like structure at the tip of the female's abdomen used to cut holes in plant tissue to deposit the eggs

References

Ives, W.H.G.; Wong, H.R. 1988. Tree and shrub insects of the prairie provinces. Can. For. Serv., North. For. Cent., Edmonton, Alberta. Inf. Rep. NOR-X-292. 327 p. + xii.

Rose, A.H.; Lindquist, O.H.; Nystrom, K.L. 1999. Insects of Eastern Pines. Natural Resources Canada, Canadian Forest Service, Ottawa. Revised edition. Publ. 1313. 128 p.