Pine Needle Scale
Hosts: Almost all needle-bearing conifers, but especially Mugho and Scots pines
Evidence: Look for white or yellowish oyster-shaped scales on needles. Lower branches tend to have heaviest populations of the scale (a). Yellowing and dieback can occur when populations are heavy, or trees may look gray.
Life Cycle: There are two generations per year. The red eggs, which overwinter beneath the dead female scale, hatch in spring. Reddish-brown nymphs (b) crawl out and move to a new area of the host tree. Nymphs reach maturity in mid-June and begin to lay eggs. The second generation of nymphs is found from July to September. These nymphs reach maturity in mid-August, and lay eggs which will hatch the following spring.
Management: Population evaluations can be made just before lilacs bloom to determine the extent of infestation. Low populations of pine needle scale do not usually pose a problem. When numbers reach several scales per needle, yellowing, stunting and eventual dieback may result. Evaluate the number of white flecks which appear in early spring. Natural enemies, such as parasitic wasps and lady beetles, feed on the scales and are often present in large numbers. Dormant oil may control scale while minimizing harm to these beneficial insects. Crawlers may be treated with summer oil .
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.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 109-110;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 108-109;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 69-70;
Rose, A.H. and Lindquist, O.H. 1973. Insects of Eastern Pine . Canadian Forest Service Publication 1313. p 63.