153 



Various approaches have been used to control gypsy moth infestations. Pesticide 

 spraying and silvicullural treatments have proven to be effective in controlling or 

 minimizing gypsy moth damage, but have not stopped the spread of the pest into new 

 areas. The Forest Service spent approximately $10.6 million on gypsy moth suppres- 

 sion and eradication efforts in fiscal year 1993. It is currendy employing biotechno- 

 logical methods to engineer more effective control agents to curtail the gypsy moth. 

 Although the gypsy moth has encountered many native North American enemies, 

 native predators and parasites have not been able to stop the spread of infestauons. 

 Naturally occurring nuclear polyhedrosis virus (NPV) is specific to the gypsy moth and 

 has proved devastaung to its survival. Unfortunately, the specific NPV has relatively 

 limited natural occurrence. A solution containing the virus has been developed into 

 a spray and is being tested under opcrauonal condidons (Cunningham el al 1993). 

 Over 50 exouc parasites and predators have been released over the years to control 

 the pest (Burgess and Grossman 1929. Campbell 1975, Drost and Carde 1992). In 

 1989, an exotic fungus, Entomophaga maimaiga, caused high mortality in gypsy moths 

 in New England (Andreadis and Weseloh 1990, Hajek et al. 1990). This fungus was 

 originally introduced to control the gypsy moth in 1920, but previously has not had a 

 significant impact. Research is currendy being conducted to examine the efficacy of 

 this fungus as a biological control agent (Hajek and Roberts 1992, Weseloh and 

 Andreadis 1992). 



White Pine Blister Rust 



Wliiic pine blister rust is a disease that infests five needle pines (Pinus subgenus 

 Strobus) throughout North America. The disease is caused by an exotic fungus, 

 Cmnartium nbicola, that was introduced to the continent on imported nursery stock in 

 diree separate locauons: Kansas (1892), eastern Canada (1906), and western Canada 

 (1921) (Micike 1938. cf. Garrett 1986). From eastern Canada, it quickly spread 



Satural range oj eoitern whtU fnru in the Unxttd SUiUi 



throughout eastern white pine {Ptnus strobus) populations in the Northeast and Great 

 Lakes region, followed by southward migration to high-elevation populations in 

 North Carolina. In the Pacific Northwest, die disease spread throughout the ranges 

 of its host trees, moving southward through California and into New Mexico (USDA 

 Forest Ser\ice 1991b). Western white {P. monticola). sugar {P. lambertiana) , whitebark 



