Pine Bark Adelgid

Contact: Eric Day, Manager, Insect Identification Laboratory

Publication 444-245, August 1996

Pine Bark Adelgid

Distribution and Hosts

The pine bark adelgid was introduced from Europe and is now widely distributed in North America, occurring principally throughout the native range of eastern white pine. This insect is also found on Scots and Austrian pine.
Pine Bark Adelgid, close-up.

Description of Damage

Adelgids feed on tree trunks by sucking sap from the phloem tissue. Trunks of heavily infested trees often appear white- washed from the woolly masses these tiny insects secrete over themselves for protection. Small nursery stock, ornamental trees, and trees in parks can be heavily attacked. However, if the trees are otherwise healthy, permanent damage should not result. In eastern white pine plantations of a forest setting, repeatedly infested mature pine trees apparently suffer no serious harm.

Identification

Adelgids are similar to aphids, except they have shorter antennae and lack cornicles (or bumps) on their abdomen. They live under a woolly mass they secrete for protection. If this mass is pulled off the trunk, black teardrop-shaped insects with short legs are revealed. When populations are high, the woolly masses coalesce into one large mass on the trunks.

Life History

Overwintering immature adelgids will begin feeding during the first days of warm weather, and secrete woolly tufts. Once these insects develop to adults (April to May), egg laying begins. Eggs hatch into crawlers, which can move to other parts of the tree or be blown to other trees. Crawlers either become winged or wingless. The wingless forms remain on the host and reproduce repeatedly. Winged forms can disperse to new trees. Five generations have been recorded as far north as the Lake States.

Control

Since permanent damage to trees is unlikely, little research has been carried out on control tactics. Application of insecticides is recommended for the trunks of transplanted large pine stock before the trunk is wrapped. Dormant oil, soap, and sevin are recommended compounds. Consult the Pest Management Guide for Horticultural and Forest Crops, Virginia Cooperative Extension Publication 456-017 for proper application methods and any additional compounds. Application of insecticides on ornamental trees should only be attempted when trees appear to be damaged and declining due to the adelgid infestation. Timing of application should be in April or May. Repeat application two to three weeks afterwards. Don't fertilize infested trees, as the adlegids will benefit from the added nutrients.

Pine Bark Adelgid