Diprion similis (Htg.)

pdf version


The introduced pine sawfly was first recorded in North America in 1914 at New Haven, Connecticut on nursery stock from Holland and has since spread throughout most of northeastern North America. It attacks trees of all sizes, but can especially be a problem on nursery and plantation trees. In heavy infestations trees may be completely defoliated in one year, with resulting branch or tree mortality.


In Maine this defoliator is most common on eastern white pine, but may occur on Austrian, Scotch, red, jack and Mugho pine as well.

Introduced Pine Sawfly Larva
Introduced Pine Sawfly Larva
Photo: Steven Katovich, USDA Forest Service,

Life Cycle and Habits

There are one to two generations annually. The fly-like adults first appear in the spring and lay eggs in slits cut in the needles in May and June. The young larvae feed gregariously and eat only the outer more tender parts of the needles. They feed individually as they mature devouring entire needles. The larvae have black heads and greenish bodies with many yellow or black spots on the sides and a double brownish-black stripe down the back. The coloration gives the larvae a "marbled" effect. Due to the extended nature of adult emergence in the spring and an overlapping of generations, both larvae and adults may be found throughout most of the summer. Larvae are most abundant in August and second generation larvae may feed until September. When fully grown, the larvae spin tough brown papery oval cocoons about the size of gelatin pill capsules which may be found attached to the twigs or in the duff. The larvae overwinter in these cocoons as pre-pupae and pupation is completed in early spring.


The insect usually begins from a very localized infestation and spreads. Caught early enough it can usually be brought under control easily by spraying the needles soon after the larvae become active and while they are still gregarious with any of the following pesticides: acephate, carbaryl, or imidacloprid. Be sure to refer to the pesticide container label for specific use instructions.

Pesticidal soaps (such as Safer's Insecticide Soap), an alternative to petrochemical pesticides, are also registered for control of sawflies.

*NOTE: These recommendations are not a substitute for pesticide labeling. Read the label before applying any pesticide. Pesticide recommendations are contingent on continued EPA and Maine Board of Pesticides Control registration and are subject to change.


For your own protection and that of the environment, apply the pesticide only in strict accordance with label directions and precautions.

Maine Forest Service - Forest Health and Monitoring Division
April 2000

For More Information:
BugWood WikiExternal Link
USFS FIDLExternal Link