DISCUSSION 



Although damage due to gouty pitch midge amounted to 

 an average of only 6 percent of the new shoots, differences 

 among stands were statistically significant. The differ- 

 ences were associated with geographic area. The stands 

 with the highest resistance were located in the north- 

 central portion of the collection area, namely in the ex- 

 treme northern portion of Idaho and adjacent areas of 

 northeastern Washington and northwestern Montana. 

 The areas farther east, west, and south were more suscep- 

 tible. Also, the most susceptible stands were those that 

 were farthest away from the planting site. These collec- 

 tions came from the area just north of the Salmon River 

 in Idaho. 



Little is known about the environmental requirements 

 of GPM. But the insect shows up most frequently in areas 

 that are cool and moist, such as northern Idaho and adja- 

 cent areas. This would explain the higher resistance ob- 

 served in the populations of pine from these areas and 

 conversely would explain the higher susceptibility of 

 populations from the warm-dry portions of the collection 

 area, that is, central Washington and areas just north of 

 the Salmon River of Idaho and in the Bitterroot Valley of 

 Montana. 



There is no doubt that the midge can cause damage se- 

 vere enough to cause mortality, and therefore it is difficult 

 to understand why there would be no growth loss on more 

 moderately infested trees as suggested by Bedard and 

 Ferrell (in press). An epidemic would not have to last 

 long before the amount of mortality would significantly 

 impact stocking. Fortunately, in 1987, the insect appears 

 to be decreasing and the epidemic may have passed. 



CONCLUSIONS 



The finds of this study emphasize the need to consider 

 resistance to pests when provenence testing. Movement 

 of seed from one area to another without this knowledge 

 could result in unacceptably high levels of damage and 

 mortality in areas reforested with seedlings having little 

 or no resistance to a specific pest. 



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Austin, L.; Yuill, J. S.; Brecheen, K. G. 1945. Use of shoot 

 characters in selecting ponderosa pines resistant to 

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Duffield, J. W. 1985. Inheritance of shoot coatings and 

 their relation to resin midge attack on ponderosa pine. 

 Forest Science. 31: 427-429. 



Bedard, W. D.; Ferrell, G. T. [Personal communication]. 

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 Berkeley, CA: U.S. Department of Agriculture, Forest 

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Bedard, W. D.; Robertson, A. S.; Ferrell, G. T. 1989. 

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Eaton, C. B.; Yuill, J. S. 1960. Gouty pitch midge. For. 

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Ferrell, R. T.; Bedard, W. D.; Westfall, R. D. 1989. Geo- 

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Hoff, R. J. 1988. Resistance of ponderosa pine to the gouty 

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