Egg -The newly laid egg is whitish, smooth, shiny, and translucent. It is about 0.2 mm long and 0.6 mm wide.
Larva -The newly hatched larva is about 0.6 mm long with a whitish body and a brownish, transparent head. When fully grown, the larva is nearly 26 mm long and has a bright-red head. The body varies from pale whitish yellow to deep yellow and is marked by two to four rows of black spots on each side of the abdomen. The last abdominal segment has a large, black patch on each side.
Cocoon -The pupa is in a reddish-brown, papery, tough cocoon that is cylindrical with rounded ends. The male's cocoon is about 8.5 mm long; the female's, about 10 mm long.
Host Plants -Although the redheaded pine sawfly was first described in 1858, serious outbreaks and the killing of host trees were not common until the establishment of pine plantations. Preferred hosts are jack, red, shortleaf, loblolly, slash, longleaf, pitch, and Swiss mountain pines. White pine, larch, deodar cedar, and Norway spruce may also be defoliated, especially when they are growing close to trees of preferred species. Redheaded pine sawflies lay eggs only on hard pines. This insect preferentially feeds on young trees (0.3 to 5 m tall). In the South it also seems to prefer trees in shaded areas.
Damage -Complete defoliation kills small trees, whereas less extensive feeding results in poor diameter growth and stunted height growth. Defoliated branches often die.
Life History -Winter is spent as a prepupa in a cocoon spun in the litter or in topsoil beneath the host. Pupation occurs in early spring, and the adults appear in a few weeks. Some prepupae may remain in a resting state (diapause) over several seasons before emerging. Eggs are deposited in the tissues of the current or previous year's needles. A single female lays about 120 eggs, which are generally clustered on needles of a single twig. Egg-laying may occur before mating, the unfertilized eggs producing only male progeny. The eggs hatch in 3 to 5 weeks. The larvae feed in clusters of up to 100 for 25 to 30 days, sometimes completely defoliating a tree from the top downward before they reach maturity. They may abandonthe tree and migrate for several yards in search of new foliage. Fully grown larvae drop to the ground, enter the soil, and spin their rough, reddish-brown cocoons, where they spend the winter. In the South there may be five generations per year.
In forests some natural control is achieved by rodents, which destroy large numbers of cocoons. Diseases and temperature extremes often kill many larvae. Also, 58 species of parasites and predators of the redheaded pine sawfly have been reared in the United States and Canada. When only a few colonies of larvae are present on small roadside, ornamental, or plantation trees, they can be picked or shaken from the trees and trampled underfoot. For specific chemical controls, see the current state extension service recommendations.
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