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PINE BARK ADELGID

James R. Baker, Extension Entomologist Emeritus

CAUTION: This information was developed for North Carolina and may not apply to other areas.
Formerly called the pine bark aphid, Pineus strobi (Hartig), Phylloxeridae: HOMOPTERA

General Information

adelgid close up
Pine bark adelgid.  A, Wingless adult and her eggs (top portion of fluff removed).  B, Crawler.  C, White, fluffy residue covering adelgids and eggs
on white pine stem.

 

The pine bark adelgid is small (about 1/32 inch), dark reddish purple, and covered with a white, fluffy secretion. Some adults have two pairs of wings.  The threadlike mouthparts are about 1/16 inch long. The egg is milky to light yellow-brown. As the embryo inside it matures, the egg darkens. The eggs are also hidden in the white, fluffy secretion. Pine bark adelgid crawlers are very small, flat, naked insects that move about actively. Nymphs resemble adults but are smaller. At first naked and yellow, nymphs soon darken and secrete fluffy, white threads.  Reports of this insect as a pest of white pines in NC have greatly declined since the 1990's. It is rarely reported anymore. It is unclear if this is related to the introduction of the Multicolored Asian ladybeetle.

BIOLOGY

 The pine bark adelgid occurs over most of the United States wherever white, Scots and Austrian pines grow. Found mostly on white pine, the pine bark adelgid occasionally infests Scots, Austrian and other pines. This adelgid is more unsightly than injurious on older trees, but it may seriously damage newly planted trees in parks, landscapes, nurseries and Christmas tree plantations.  On heavily infested trees, the needles turn yellow. Small trees may be stunted or killed.  

Pine bark adelgids are the most commonly reported pests of white pine. These adelgids are often confused with woolly aphids or mealybugs or even fungi because of the fluffy secretions that cover the adelgids. The winter is spent as wingless females in crevices and rough places on the bark although with heavy infestations, most of the bark may be completely covered.  In late winter, development resumes and each female lays up to 24 eggs under and around her body in her fluffy, white secretion. After laying her eggs, the female dies.

adelgids on barkFrom the eggs hatch crawlers that move actively on the stems and needles seeking a place to feed. Once a crawler settles down  to  feed  under  a  needle  fascicle  or crevice on the bark, it does not move again until the next molt. Crawlers may move from plant to plant by crawling or on wind currents or perhaps on the feet of birds. Most develop into wingless females that lay fertile eggs without mating. Winged pine bark adelgids apparently fly to spruce, but they do not successfully reproduce there. There are 5 or more generations per year.  

heavy infestation on white pine trunkPopulations of pine bark adelgids increase dramatically during cool fall weather and in early spring. Predaceous insects often lower populations suddenly as the weather warms up in late spring. Although an infested tree may have conspicuous patches of white, fluffy wax, during the summer the actual number of live adelgids is usually very low.

Control

 Maggots of hover flies and other flies and lady beetle larvae feed on pine bark adelgids in warm weather. Trees that are heavily infested and are showing symptoms of decline should probably be sprayed for adelgid control. Horticultural spray oil can be applied during the winter and before new growth emerges in spring. Oil sprays may damage white pine during the growing season, especially in dry weather.      

Pesticide (Trade Name) 
Formulation
Remarks
*imidacloprid (Merit) 75 % wettable powder  follow label directions
*oil, summer or horticultural 98 to 99 % emulsifiable concentrate 2 1/2 to 10 tablespoons per gallon of water
*soap (Insecticide Conc., M-Pede) 50.5 % emulsifiable concentrate 4 ounces per gallon of water

* Suitable for home use.

Other Resources

For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service personnel.

Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance contact an agent of the North Carolina Cooperative Extension Service in your county.

Prepared by: James R. Baker, Extension Entomologist Emeritus

ENT/ort-62 January 1995 (Revised) 2000
Web page last reviewed January, 2011 by the webperson.