European pine sawfly has hatched
throughout the state. This insect appears as groups of
larvae feeding on the needles of mugo, Scotch, and other
pines. Larvae are elongate, caterpillarlike creatures, with
several stripes of various shades of green. They have large,
black heads. They are not caterpillars; they pupate and
emerge later in the year as wasplike insects. Caterpillars
have three pairs of true legs and up to five pairs of
prolegs (leglike structures on the abdomen). Sawfly larvae
also have three pairs of true legs, but they have six or
more pairs of prolegs.
Larvae feed on second- and third-year
needles, maturing and dropping from the plant to pupate
beneath the tree by the time the current year’s needles are
emerging from the candles. The presence of these new needles
will keep defoliated branches from dying, but damaged twigs
will be leafless except for the current year’s needles
appearing as a tuft on the end.
Because these insects feed in groups, they can easily be
removed by hand. Larger populations can be controlled with
sprays of many chemical insecticides. Because these are not
true caterpillars, Bacillus thuringiensis kurstaki (Bt)
sprays will not be effective.