Introduced Pine Sawfly
Hosts: Preferred hosts are white and Scots pines, but jack, red, and Swiss mountain pines may be attacked
Evidence: Larvae are marbled yellow-green with black stripes down the back and yellow and white spots on the sides (a). They may be found between late May and early July (first generation) and between late July and early September (second generation). Look for defoliation of current year's and older foliage. Young larvae feed in groups, while older larvae feed singly.
Life Cycle: There are two generations per year. The larvae overwinter in cocoons in foliage, on twigs, other trees, shrubs, or other understory objects (b). Pupation takes place in early spring, and adults emerge during May and early June. Eggs are laid in slits in needles.
Management: Trees of all ages are attacked, but the insect seems to prefer ornamental, nursery, or plantation trees. First generation larvae prefer previous year's needles but second generation will feed on old and current year foliage. Very low or rapidly shifting temperatures or heavy rainfall can reduce egg and early larval populations. Natural enemies include birds, which feed on pupae, and several parasitic wasps. Bacillus thuringiensis cannot be used successfully, but various chemical insecticides are effective against larvae.
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.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 395-396;
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 74;
Rose, A.H. and Lindquist, O.H. 1973. Insects of Eastern Pine . Canadian Forest Service Publication 1313. p 54.