162 



tions have been decimated (Langdon, personal communication; Windham, penonal 

 communication). Qones of these trees have shown varying degrees of resistance 

 under greenhouse and Celd test conditions (Windham et aL, unpublished) and have 

 been integrated into a breeding program. 



Hemlock Woolly Adelgid 



The hemlock woolly adelgid (Addges Isugiu) attacks eastern hemlock {Tsuga canadensis), 

 a commercially important species in eastern forests. The insect is believed to have 

 been introduced into the U.S. from Asia {cf. McClure 1991) and was first reported in 

 the Pacific Northwest more than 65 yean ago (Annand 1924). The insect was first 

 observed in eastern forests approximately 40 years ago in Virginia. The hemlock 

 woolly adelgid has spread north into southern New England. The adelgid thrives in 

 colder temperatures and is, therefore, likely to infest eventually the entire Northeast 

 and eastern Canada (McQure 1989). A rapid increase in infested acreage was report- 

 ed in New York in 1990. and northern New Jersey has 26,000 acres of infested hem- 

 lock. Apparently it is not spreading south as rapidly, as it has not yet been found in 

 North Carolina (Langdon, personal communication). 



Natural mnge oJiasUm htmlcA m iht Vmttd Stala 



The adelgid probably injects the hemlock trees with a toxic saliva during feeding, as 

 with the related balsam woolly adelgid (McQurc 1991). Symptoms arc foliage discol- 

 oration and dead branches. The tree usually dies within four years. All hemlocks are 

 affected in a similar fashion, irrespjcctive of age and size. Other introduced insccu, 

 the elongate and circular hemlock scales, have been found in conjunction with the 

 adelgid (Burkman el aL 1993). These insecu were introduced from Japan. Both scales 

 can we». en and kill hemlocks, although not as rapidly as the adelgid (Stevens, per- 

 sonal communication). 



No resistance to the adelgid has been recorded in eastern hemlock nor has effective 

 biological control(s) been found. Pesdcides, horticultural oil, and insecticidal soap 

 have been effective in controlling infestation in nursery and urban plantings 

 (McQure 1987). However, these methods are not applicable to or only partially effcc- 



