Redheaded Pine Sawfly
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Hymenoptera: Diprionidae Hosts: Preferred hosts are red, Scots and jack pines. Also attacked are shortleaf, loblolly, slash, pitch, Swiss mountain, Japanese black, mugho pines, white pine, larch, deodar cedar, and Norway spruce Evidence: Look for sites where eggs have been laid in current or previous years' needles. Larvae, which have reddish heads and whitish-yellow bodies with 6 rows of black dots (a), are present from May through September. Look for defoliation caused by larvae feeding gregariously on old and new foliage and tender bark. They tend to defoliate an entire branch before moving on another area of the tree. Fascicle sheaths or tufts of curled, strawlike needles may remain after larvae feed. |
a. Larva of the Redheaded pine sawfly |
b. Red pine defoliated by Redheaded pine sawfly larvae. |
Life Cycle: There is one generation per year. Winter is spent as a prepupa in topsoil or duff. Adults emerge in early spring and lay eggs in slits in current or previous years' needles. Eggs hatch in 4 to 5 weeks. A range of larval age groups may be present throughout the summer. Young larvae feed on the edges of needles, leaving a central spine, but large larvae consume entire needles. Damage tends to be worse in years with warm, extended falls. From July through September, larvae reach maturity and drop to the soil to overwinter.
Management: Larvae may defoliate an entire tree from the top downward (b). Young or stressed trees are preferred, and small ornamental pines may be completely defoliated and killed in heavy infestations. Trees that are growing in poor sites or under stress are attacked more readily than healthy trees. Damage can sometimes be reduced by getting rid of competing vegetation, planting in high-quality sites, and promoting early closure by close plantings. If infestations are light, manual removal of larvae may effectively control the pest. When infestations are heavy, or many trees are involved, trees may be sprayed with a residual insecticide.
Photo Credits:
Figure a: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Figure b: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
References:
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 384-385;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 16-19;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 44-47;
Rose, A.H. and Lindquist, O.H. 1973. Insects of Eastern Pine . Canadian Forest Service Publication 1313. p 51.
