Forest Pests: Insects, Diseases & Other Damage Agents

Balsam Shootboring Sawfly
Pleroneura brunneicornis Rohwer

Hanson, T., and E. B. Walker. [n.d.] Field guide to common insect pests of urban trees in the Northeast. Waterbury, VT: Department of Forests, Parks and Recreation. http://www.state.vt.us/anr/fpr/forestry/pubs/pest.html

Hymenoptera: Xyelidae Hosts: Balsam, Fraser and white fir Evidence: Larvae tunnel into the center of new shoots, causing the needles to turn red and die. Initially, the affected shoot has a flattened appearance and just the center turns red (a). As the shoot elongates, the dead tip becomes more obvious and looks much like frost damage. Unlike with frost, the dead tip is easily pulled off, revealing a white larva or hollowed-out shoot (b,c). After the larvae leave the shoots (by mid-June in northern New England) the affected part usually drops. Damage tends to be heaviest in even years. Life Cycle: The sawflies overwinter as either larvae or pupae in earthen cells in the soil. Adults, which emerge in early spring, lay eggs through the bud sheath before buds swell. Upon hatching, the young larva feeds toward the tip of the shoot in the needle cluster. Later, it burrows into the shoot and tunnels towards its base. When mature (6-7 weeks), the larva crawls out of the shoot, burrows into the ground, and spins a thin cocoon. In more northerly regions, the insect may spend nearly two years in the cocoon.	a. Early sign of damage
	b. Larva feeding on developing shoot
	c. Late sign of damage. Note resemblance to frost injury

Management: Keeping trees healthy and tightly sheared, where appropriate, will help minimize the damage caused by this insect. This pest is most prevalent in areas adjacent to native balsam fir stands.

Photo Credits:

Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.

Figure b: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.

Figure c: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT

References:

Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 378;

Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 20;

Martineau, R. 1984. Insects Harmful to Forest Trees . Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 103;

Rose, A.H. and Lindquist, O.H. Revised by Syme, P. 1994. Insects of Eastern Spruces, Fir and Hemlock. Canadian Forest Service Publication. p 38-39.

[ Contents ]     [ Previous ]     [ Next ]     [ Home ]