Landscape - Sawflies on Pines

Sawflies can cause significant damage to pines in the late summer. The following is more information.

Sawflies are members of the same insect order (Hymenoptera) that includes ants, bees, and wasps. The larval stage has a caterpillar-like body that may be brightly marked with stripes or spots. Some species change significantly in appearance as they grow, making identification confusing. Large numbers of sawflies can strip the needles from a tree in a short period. Several species can be found on pines in Delaware.

Feeding is most severe in the crown to upper half of the tree but heavily infested trees can be completely defoliated. If this occurs after the winter buds have formed, many branches or even the entire tree can be killed. There are two generations each year in some sawflies. The second generation feeds on both old and new needles during August and September.

Sawfly populations are usually controlled by combinations of natural enemies, predators, starvation, disease, or unfavorable weather. Outbreaks can occur when natural control does not produce high mortality. Regular inspection of pines will help to detect sawfly infestations before the larvae reach a size that can cause significant defoliation. Since eggs are laid in clusters, feeding by groups of larvae can cause unsightly damage to ornamental or landscape plantings, as well as nursery trees.

If only a small number of colonies are present and accessible, they can be handpicked, shaken off, or pruned from the tree and destroyed. Some of the insecticides that can be used for sawfly are acephate, bifenthrin, carbaryl, esfenvalerate, and permethrin. Although sawflies look like caterpillars, they are not susceptible to Bt sprays.

Adapted from "SAWFLIES - LATE SEASON PINE DEFOLIATORS" By Lee Townsend in the August 18, 2008 edition of the Kentucky Pest news from the University of Kentucky, College of Agriculture.