Pine leaf adelgid

Distribution

Canada

Canada and north eastern United States (Maine, New Hampshire, Vermont and New York)

Micro-habitat(s)

Annual shoot

Damage, symptoms and biology

The pine leaf adelgid, sometimes called the pine leaf chermid or the pine leaf aphid, is a native insect that occurs on both white pine and spruce. It is regarded as a very important pest of white pine where it grows adjacent to red and black spruce in the Maritime Provinces. It causes galls or swellings on the new shoots of red and black spruce and migrates from these to the shoots of white pine. The latter phenomenon is usually observed in odd-numbered years in the Maritime provinces. The galls on spruce are unsightly but cause little injury to the tree. However, severe infestations of nymphs on white pine will kill the current year's shoots in late summer, and moderate infestations may cause the shoots to die the next spring.

This insect has a complex life cycle, and has at least five distinct forms. Forms which have wings alternate between spruce and white pine, and the complete life cycle takes 2 years.

The insect causes cone-shaped galls on spruce twigs in the spring of odd-numbered years. Winged forms migrate from the galls about mid-June to old needles of white pine, where they produce wingless offspring that crawl to the new shoots and feed by piercing the tissues. The next year winged forms develop, and these fly back to spruce. At this point, two successive wingless forms are produced, the second of which overwinters and produces the galls in the spring.

Main host(s)

Black spruce, eastern white pine, red spruce, spruces