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Disease Note.

White Pine Blister Rust in Southern New Mexico. F. G. Hawksworth, USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526. . Plant Dis. 74:938. Accepted for publication 16 July 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0938A.

White pine blister rust (Cronartium ribicola J. C. Fisch.) was found on southwestern white pine (Pinus strobiformis Engelm.) near Cloudcroft, Otero County, New Mexico, in March 1990. The closest known populations of this rust are about 1,000 km north in southern Wyoming on P. f1exilis E. James and 1,400 km west in the southern Sierra Nevada of California on P. lambertiana Douglas. Although inoculation tests have shown that P. strobiformis is very susceptible to the rust (1), this is the first report of the fungus in natural stands of this host. The extreme isolation of the outbreak suggests that it may have been a separate introduction rather than a result of spread from previously known affected areas. The oldest infected area appears to be 5 km northeast of Cloudcroft, where the rust has apparently been established for at least 15 yr and several seedlings have been killed. Scattered infected trees have been found up to 30 km south and 19 km east of Cloudcroft. Plans are being developed to survey this and adjacent areas to determine the distribution of the rust on pines and on native and cultivated Ribes spp. and to estimate how long the outbreak has been present in New Mexico.

Reference: (1) R. Hoff et al. Eur. J. For. Pathol. 10:307, 1980.