European Pine Sawfly
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Hymenoptera: Diprionidae The larvae of more than 10 species of sawfly feed on pine needles. Some of the more common species are included here. Sawfly larvae differ from the caterpillars of moths and butterflies in having more than five pairs of abdominal prolegs which lack crochets (hooked spines), while there are five or fewer pairs with crochets in Lepidoptera. Hosts: Red, Scots, white and Austrian pines Evidence: Look for defoliation that results from gregarious feeding on old foliage only (a). Only fascicle sheaths may remain, or you may see tufts of curled, strawlike needles from early feeding. Larvae, which are 18-24 mm when full-grown, tend to eat all foliage on one branch before moving to another. They are grayish-green with black heads and thoracic legs, and a pattern of light and dark green or black stripes (b). Life Cycle: There is one generation per year. Overwintered eggs hatch from April to mid-May. Larvae are present until mid-July. Then they may drop to the ground or remain in the tree to pupate in golden-brown cocoons. Adults emerge from late August through September. Sawfly adults lay eggs in slits in needles during late September through October (c). |
a. European pine sawfly larvae feed gregariously on previous years' foliage. |
b. Larvae of the European pine sawfly are often seen in pairs on individual needles. |
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c. Eggs of the European pine sawfly are laid in slits in needles in the fall. |
Management: The European pine sawfly limits its feeding to old foliage and seldom kills trees, though shoots may die or be deformed and losses in diameter growth and height may occur. Bark of new shoots may also be eaten. Numerous parasites and disease pathogens are associated with these sawflies, and they can be effective control agents. Bacillus thuringiensis cannot be used successfully, but various chemical insecticides are effective against larvae.
Photo Credits:
Figure a: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Figure b: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Figure c: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
References:
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 391-392;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 16-19;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 73;
Rose, A.H. and Lindquist, O.H. 1973. Insects of Eastern Pine . Canadian Forest Service Publication 1313. p 45, 48-50.
