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.