
                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, April 27, 1995                   TAG: 9504270023
SECTION: CURRENT                    PAGE: NTV-5   EDITION: NEW RIVER VALLEY 
SOURCE: JOE HUNNINGS
DATELINE:                                 LENGTH: Medium

HEMLOCK WOOLLY ADELGID SHOULD BE TAKEN SERIOUSLY

If you have hemlocks in your landscape, you probably have seen - or soon will encounter - a fuzzy white mass growing at the base of needles. Take note! It's hemlock woolly adelgid, a serious pest! Get in the habit of searching for it and controlling it early.

The hemlock woolly adelgid (pronounced uh-DELL-gihd), believed to be native to Asia, was introduced into the United States in 1924 and has become a serious pest of eastern hemlock and Carolina hemlock. In Virginia, it is established along the mountainous regions of the Shenandoah Valley, spreading southward along the Blue Ridge Mountains. It first became a pest concern in the New River Valley several years ago.

Identification

Sacs at the base of the needles are good evidence of a hemlock wooly adelgid infestation. These sacs resemble the tips of cotton swabs. They are present throughout the year, but are most prominent in early spring. Adelgids display several different forms during their life history, including winged and wingless forms. Generally, they are brownish-red in color, oval in shape, and approximately 0.8 millimeters in length.

Crawler stage nymphs produce the white cottony sacs, which cover their bodies and remain in place throughout their lifetimes.

Damage

The hemlock woolly adelgid feeds during all seasons, with the greatest damage occurring in the spring. It is dispersed by wind, birds and mammals.

By sucking sap from the young twigs, the insect retards or prevents tree growth, causing needles to discolor from deep green to grayish-green and drop prematurely. The loss of new shoots and needles seriously impairs tree health. Defoliation and tree death can occur within several years.

Control

Application of insecticides is recommended to control the hemlock woolly adelgid. The best compounds are horticultural oils, which smother the insects. A 1 percent solution is recommended from May through September, and a 2 percent solution from October to April. Complete coverage of the tree is necessary and can result in 100 percent mortality of the adelgids. Only one complete application of oil is necessary. Following treatment, monitor the situation.

Ironically, tree fertilization can result in more damage, as adelgid populations are known to flourish on such trees.

Researchers currently are investigating the prospects of identifying and importing natural enemies for use against this pest.

by CNB