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Pine bark adelgids can nearly coat the surface of pines.

Pine Bark Adelgid

Pine bark adelgid females lay masses of eggs in cottony wax threads.

Species: Pineus strobi (Hartig)


Distribution: North America and Europe


Hosts: Mainly attacks eastern white pine but can infest Scotch, Ponderosa, jack and pitch pines.


Damage:

Heavy infestations on branches of pines will cause stunted growth. Foliage may become blackened from a fungus growing on the honeydew and wax produced by the nymphs and adults. Occasionally even tree death may occur. This pest usually does not attack smaller trees.


Description and Life Cycle:

This pest is often called an aphid though adelgids do not have the long antennae and cornicles typical of aphids. The life cycle of the pine bark adelgid is not well understood. Apparently, immature females overwinter attached to the bark of pines. When the spring temperatures reach 50F, these nymphal females become active and are soon covered with a white woolly wax. By late April, the nymphs mature and molt into wingless adults. These females lay 40 to 50 eggs in 20 to 30 days. The eggs hatch in one to two weeks and the crawlers move to suitable places on the tree to insert their mouthparts. They often hide under old dead adults on the bark, at the bases of old needles and under newly emerging needles. The new nymphs produce waxy coverings and take about 20 to 30 days to mature. This pest may have up to five overlapping generations in a season with adults, nymphs and crawlers present throughout the summer. Adults and young nymphs apparently die during the winter; only the nymphs which have molted twice, third instars, can overwinter.


Control Hints:

This pest is slow to spread because the crawlers have to drop from adjacent trees, be wind blown, or hitch a ride on birds or other animals found in the plantation. Older stands of white pines surrounding plantations should be removed.

Option 1: Biological Control - Encourage Natural Predators and Parasites - Many lady beetles, lacewings and hover flies attack the pine bark adelgid. These are usually not effective in Christmas tree plantations because of the use of insecticides sprayed for other pests. Be careful to not misidentify the lady beetle larvae which are often covered with white woolly material and look much like the adelgids.

Option 2: Chemical Control - Dormant Oil Sprays - Dormant oil sprays (3-5%) are quite effective if applied in the fall or spring to kill the overwintering nymphs. Be sure to spray in the spring before the females have begun to produce eggs in the waxy coating. Thorough coverage of the trunk and branches is needed.

Option 3: Chemical Control - Insecticide Sprays - Sprays using registered insecticides, applied in mid-April will kill the overwintering nymphs before they mature and lay eggs. Summer sprays are effective but two to three sprays, at weekly intervals, will be needed to kill new crawlers hatching from resistant eggs.