Sawflies are members of the insect order 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 needles from a tree in a short period. Several species can be found on pines in Kentucky.
The introduced pine sawfly (Figure 1) is one that is active into fall. It has a black head and black body that is covered with yellow and white spots. This sawfly prefers the needles of eastern white pine but also will eat Scotch, red, Austrian, jack, and Swiss mountain pine. Short leaf and Virginia pines have been attacked but usually are not heavily damaged.
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 winter buds have formed, many branches, or even the entire tree, can be killed. There are two generations each year; the second generation of this sawfly feeds on both old and new needles during August and September. 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
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. Although sawflies look like caterpillars, they are not susceptible to Bt sprays.
- Regular inspection of pines will help to detect sawfly infestations before larvae reach a size that can cause significant defoliation.
- 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 control are listed below (common name of the active ingredient followed by an example brand name).
- Acephate – Orthene Turf, Tree & Ornamental Spray
- Bifenthrin- Ortho MAX Lawn & Garden Insect Killer
- Carbaryl – Sevin
- Cyfluthrin – Bayer Multi-Insect Killer Concentrate
- Permethrin – Ortho Tree, Shrub, and Lawn Spray.
By Lee Townsend Extension Entomologist