Pine Leaf Adelgid
Hosts: White pine, red and black spruce
Evidence: Beginning in mid-summer, look for drooping or discolored new lateral shoots on pine (a). Crawlers will be present on the shoots and remnants of the winged adults may be found lined up on old pine needles, heading toward the needle base, from July to May (b). This shoot droop may persist on the tree into the following year. Heavy populations occur on pine and spruce in alternate years.
Life Cycle: The pine leaf adelgid has a complex life history which occurs over a two year period and involves two hosts and five distinct life stages. From the discolored shoots, a winged form of the adelgid is produced which flies to spruce and causes production of leafy, cone-like galls at the tip of the new growth in the spring. Heavy production of galls on spruce may indicate that there is a threat of high populations on pine the following year.
Management: The mortality of young shoots during infestations appears to become a limiting factor, contributing to population collapse. On ornamental spruce, control may be effected by hand-collecting and burning galls before mid-June. To date, insecticidal treatments have proven ineffective.
Similar Species: See spruce gall adelgids.
Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Figure b: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 86;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 76-77;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 57-59;
Rose, A.H. and Lindquist, O.H. 1999. Insects of Eastern Pines. Canadian Forest Service Publication 1313. p 38.