SUSCEPTIBILITY OF PONDEROSA PINE TO ENDOCRONARTIUM-HARKNESSII AND OTHER CAUSES OF MORTALITY IN PENNSYLVANIA

The effects of Endocronartium harknessii on provenances of Pinus ponde rosa planted in 1969 on a coal strip-mine spoil bank in central Pennsy lvania were reassessed. In 1982 infection levels among seed sources ra nged from 4.9 to 52.5%. In 1991 infection levels ranged from 29 to 95% , and mortality due to rust infection ranged from 9 to 58% among these seed sources. Levels of infection, mortality due to rust infection, a nd mortality unrelated to rust infection differed significantly among seed sources (P < 0.001, < 0.001, and = 0.023, respectively). Among ge ographic ecotypes, there were no significant differences among percent ages of trees infected (P = 0.094), but there were significant differe nces among trees surviving outplanting (P = 0.007), mortality due to r ust (P = 0.004), and mortality unrelated to rust (P < 0.001). Only one provenance incurred less than 40% infection, indicating that virtuall y none of these types of provenances are suitable for reforestation in areas of eastern North America where E. harknessii occurs.