Cronartium comandrae on Pinus contorta var. latifolia in North Dakota. J. A. Walla, Plant Pathology Department, North Dakota State University, Fargo 58105. . Plant Dis. 76:323. Accepted for publication 10 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0323E.
Cronartium comandrae Peck, cause of comandra blister rust, was found in 1990 on planted lodgepole pine (Pinus contorta Douglas ex Loud. var. latifolia Engelm. ex S. Wats.) in Pembina County in northeastern North Dakota (voucher BPI 1108275). C. comandrae has not previously been reported on pines in North Dakota or in agricultural areas of other Great Plains states. Identification of the fungus was based on the presence of obpyriform aeciospores with average dimensions of 68 X 21 µm. The diseased trees were in a windbreak of mixed pines planted during 1974-1976. Of 27 P. c. latifolia in one portion of the windbreak, 10 were infected and had a total of 46 cankers. Most cankers were from infections after 1980, although one canker covered the lower 0.5 m of the tree trunk. The rust was not found on two known suscepts, P. sylvestris L. and P. banksiana Lamb., in adjacent parts of the windbreak or on older P. c. latifolia in another part of the windbreak. It was not found on P. sylvestris. P. banksiana, or the known suscept P. ponderosa Douglas ex P. Laws. & C. Laws. in nearby plantings or on P. c. latifolia in plantings elsewhere in North Dakota. The alternate hosts Comandra and Geocaulon were not found in or near the windbreak, but Comandra has been reported from Pembina County and from prairies across the Great Plains. Because P. c. latifolia has been considered a possible alternative pine for future planting in North Dakota, the threat of this disease should be recognized.