155 



Most of the five needle pine species are harvested commercially, particularly eastern 

 white and western white pines. These two species are particularly valuable in forest 

 ecosystems, as they often dominate forest stands over significant areas within their 

 respective ranges (USDA Forest Service 1991b). Other species of white pine are not 

 commercially important, but occupy critical ecological niches. Some white pines pro- 

 duce large seeds that are extremely nutritious and important in wildlife food chains. 

 For example, whitebark pine seeds in the Rocky Moimtains serve as a major food 

 source for grizzly bear, black bear, red squirrels, and Clark's nutcracker (KMidall and 

 Arno 1989). 



Balsam Woolly Adelgld 



True firs of the genus Alnes in North America are attacked by the balsam woolly adel- 

 gid (Adelges piceae). The adelgid was introduced into New England in 1908 on Euro- 

 pean nursery stock (Kolinsky 1916). The adelgid can cause physical damage by feed- 

 ing, although chemically induced injury is the major cause of mortality. The salivary 

 secretions of the adelgid change the balance of growth hormones and inhibitors and 

 cause abnormal development of tissues in trees (Balch et aL 1964). The tissue is killed 

 by a combination of factors associated with salivary secretions (cf. Hay 1978) and the 

 infected tree can die within 2-7 years (Johnson 1980). 



In the East, the balsam fir (,Abies balsamea) is infested from northern New York into 

 the Canadian Maritime Provinces and the Gaspe region of Quebec (Mitchell et al. 

 1970). Severe damage of balsam fir populations can occasionally occur. West coast fir 

 populations became infested in approximately 1928 from a separate European source 

 (Annand 1928). All western fir species have been infested, to varying degrees, with 

 the possible exception of the unique brisdecone fir (Abies bracUata) (vidt Hay 1978). 

 As in eastern North America, damage to western fir species can be extensive. 



Tlie eastern infestation has spread south, along the Appalachian mountains. The 

 northern bracted balsam fir {Abus balsamea var phaneroUpns) has been almost elimi- 

 nated by adelgid infestation. Tliis variety of balsam fir has a very limited distribution 

 and was restricted to two mountaintops in northern Virginia (Langdon, personal 

 communication). Prcsendy the only mature population covers less than one acre. 

 Mature populations of Fraser fir (Abits frasm) also have been severely affected. This 

 species is endemic to mountaintops in the southern Appalachians. It is the codomi- 

 nani species with red spruce (Ptcea rubms) that logciJicr constitute the spruce-fir eco- 

 systems found only at high ele\-ations in this region. Adelgid infcsutions have elimi- 

 nated mature trees from many locations. Although immature trees still persist in sig- 

 nificant numbers, these will be attacked with increasing severity as they age. 

 Therefore, the reproductive potential of the species may have been destroyed. 



Tlie North Carolina State Park Ser\icc tried intensive insecticide spraying at Mount 

 Mitchell shordy after the detection of the adelgid in 1957 Tliis technique proved 

 efTeciive in protecting indiridual trees but was ill-suited for use on a forest-wide scale. 

 Until recently, the National Park Service in the Great Smoky Mountains National 

 Park deployed an environmentally safe detergent spray to conu-ol the insect. This 

 spray -'so proved too cosdy and labor intensive to be employed on a large scale 

 (Langdon, personal communication). 



Extensive research has been conducted to locate a biological control for the adelgid, 

 but no effective biocontrol agents have been found. All apparendy suitable insects 

 were field-tested in eastern Canada over a 35-year period. No single predator or 

 group of predators was found to be effective (Schooley el aL 1984). While some fun- 



