History of the 



hfemlock Coolly K^delgid 



IN THE East 



Dennis Souto and Tom Luther 



The hemlock woolly adelgid, Adelges tsugae. was first 

 reported on eastern hemlocks in Richmond, Vir- 

 ginia, in 1953-1954. The trees were located in a 

 large municipal park (IV^aymont ParkI that originally was 

 an avid plant collector's estate. In the next 30 years 

 (1955-1985). HWA slowly spread through the Mid-Atlantic 

 states It was considered no more than an annoying orna- 

 mental pest that was controlled with some effort. For ex- 

 ample, Pennsylvania first reported it in the 1960s and 

 New York in the early 1980s — yet concern surfaced in 

 both states only in the 

 late 1980s. 



Even in Virginia, HWA 

 was considered only a or- 

 namental pest despite its 

 spread from ornamental 

 hemlocks to hemlock for- 

 ests in the early 1960s. 

 Once HWA reached Vir- 

 ginias hemlock forests, 

 the outbreak's behavior 

 changed — the rate of 

 spread and intensity of 

 damage increased sharp- 

 ly. Infested hemlocks 

 (both eastern and Caro- 

 lina) quickly began to 

 show severe stress with 

 scattered mortality occur- 

 ring at higher elevations 

 (about 2400 feet). 



Two abiotic events 

 occurred in 1985 that sig- 

 nificantly affected HWA in 

 the East. In [anuary, a se- 

 vere cold wave moved 

 across southwestern Vir- 

 ginia At elevations above 

 2000 feet, temperatures 

 of -20 to -28 degrees F 

 were common. Subse- 

 quent surveys found 



HWA absent above 2000 feet and greatly reduced at lower 

 elevations. The HWA outbreak in Virginia had been tem- 

 porarily broken. 



Hurricane Gloria battered the East Coast in September 

 1985. In 1986 HWA was found in southern Connecticut, pos- 

 sibly cartied from infested areas in Long Island by the 

 hurricane. The discover^' of HWA in Connecticut coin- 

 cided with increased visibility and concern. No longer 

 would HWA be viewed as simply an ornamental pest. 

 Between 1985-1995, HWA spread north and south 

 along the eastern sea- 

 board (See map). Con- 

 cern grew as hemlock 

 deteriorated in the old- 

 er infested areas. HWA 

 recovered slowly, but 

 steadily, from the se- 

 vere cold wave of [anu- 

 ary, 1985. in Virginia. By 

 1995, tree mortality was 

 again reported in the 

 Blue Ridge Parkway. 

 Uninfested states in 

 northern New England 

 (Vermont, New Hamp- 

 shire, and Maine) insti- 

 tuted quarantines to 

 prevent HWA from 

 reaching their consider- 

 able hemlock resources. 

 A very cold winter in 

 I993-I994 sharply re- 

 duced HWA abundance 

 again. However HWA 

 recovered steadily, just 

 as in Virginia. 



Only New York 

 reports a stop to HWA's 

 northward spread. Within 

 the Hudson River Corri- 

 dor, no new HWA infes- 

 tations have been re- 



[\iative range of 

 Eastern Hemlock 



Hemlock Vioolly 

 Adelgid reported 

 through I99S 



DECEMBER 1995 ■♦■ JANUARY 1996 



