Pine sawflies

Natural History
Female red-headed sawfly laying eggs
Photo credit: J. McGraw - North Carolina State University

Pine sawflies are insects in the genus Neodiprion or the genus Acantholyda that defoliate pines in Florida and throughout the South. There are currently around eight different species of sawflies in Florida. Sawflies usually attack only one tree or a small group of trees. Under favorable conditions, attacks by sawflies can intensify and the insects can infect thousands of acres of trees.

Sawflies prefer 5- to 10-year-old trees. Repeated attacks over 2 or more years can cause a tree to die but the greatest damage caused by pine sawflies is loss of tree growth. They create this damage by eating the needles of pines.

In the spring, female sawflies lay their eggs in the needles of pines. The female cuts an individual slit for each egg and can create 1 to 30 slits for eggs in one needle. Larvae hatch from the eggs to eat the pine needles. Fully-grown larvae drop from the needles to the ground and spin cocoons in the soil. Sometimes larvae do not drop from the tree but remain to spin their cocoons in the branches and needles of the tree. This is common when the ground is flooded. Adult sawflies emerge from the cocoon weeks, months, or even years later depending on the species.


 

Identifying Characteristics

Identifying the injury: Pine sawfly attacks are sometimes recognized when just one side of the needles have been destroyed by the larvae eating the pine needles. Remaining needles will be reddish brown. In other cases, entire branches will be without needles or only short stubs of needles will be left.
Identifying the insect: Adult females are 1/4" to 3/8" long and reddish brown in color with a blackish green abdomen and thin antennae. Adult males are 3/16" to 1/4" long and black in color with feathery antennae. Fully-grown larvae are 1" long, yellowish green to green in color, and generally have dark stripes or black spots and red or black heads.
Susceptible trees: Sawflies can infest any southern pine. Young pines, 5-10 years old, are most susceptible. Certain species of pine sawflies have preferred hosts. The red-headed sawfly prefers longleaf and slash pine. The slash pine sawfly prefers slash pine. The black-headed pine sawfly prefers loblolly and pond pine.

 

Images

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Adults of blackheaded pine sawfly (Neodiprion excitans). Egg of a conifer sawfly (Neodiprion sp.) in the needle of a white fir (Abies concolor). Larvae of redheaded pine sawfly (Neodiprion lecontei). Typical "straw"-like feeding damage done by redheaded pine sawfly (Neodiprion lecontei).
Photo credit: Gerald J. Lenhard, Louisiana State University, Bugwood.org Photo credit: Donald Owen, California Department of Forestry and Fire Protection, Bugwood.org Photo credit: Lacy L. Hyche, Auburn University, Bugwood.org Photo credit: G. Keith Douce, University of Georgia, Bugwood.org

 

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