There are numerous species of conifer-feeding sawflies, which are divided into two classes.
The spring species include the European, red, Jack and virginia pine sawflies. They generally feed on old needles.
The summer species are the introduced, white, redheaded and blackheaded pine sawflies. They primarily consume the current year's growth.
Pine sawflies can cause severe damage to forests and landscape pines. Though found in the eastern portion of the United States, each species has its own range. Most commonly, mugo, Scots, red, Jack and white pines are infested in the Northeast, while shortleaf, loblolly, longleaf, pitch and virginia pines are attacked in the Southeast.
What should I look for on trees infested by sawflies?
These may vary due to the differing feeding habits of the numerous species. The defoliation of the oldest needles gives the tree a tufted appearance, as only the new branch tip growth remains. Some will feed on tender bark, which causes branch and terminal shoots to be deformed.
Yellowish-brown, skeletonized needles are an early indicator of infestation. These needles will soon drop from the tree. Younger larvae will eat the outer part of the needles, while older larvae will consume entire needles, leading to sever defoliation. Growth reduction and tree death can result. Some southern pine species can overcome defoliation, but red, white and Jack pine often die. Repeated defoliation can also weaken a tree, leaving it vulnerable to other pests or disease. The introduced pine sawfly tends to kill its host by complete defoliation early in the season.
What causes sawflies to infest my trees?
Sawflies are actually related to wasps and ants, but are so called because the female possesses a saw-like stringer on her abdomen which is used to slice into pine needles or twigs to deposit eggs. Sawfly larvae, which resemble caterpillars, feed voraciously on pine needles. Others feed on the tender bark of twigs as well.
Solutions and treatments
Pine sawflies are attacked by many parasites and are subject to various viral and fungal diseases. Natural predators include birds and rodents.Chemical treatments and soaps, such as M-Pede, may be applied to combat the larvae as they first emerge from the eggs.