Isolation of Ceratocystis ulmi from Deep Annual Rings of Elms in California. T. E. Tidwell, Plant Pathologist, California Department of Food and Agriculture, Sacramento 95814. R. J. Sava, Environmental Hazards Specialist, California Department of Food and Agriculture, Sacramento 95814. Plant Dis. 66:1016-1018. Accepted for publication 25 January 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-1016.

The Dutch elm disease fungus, Ceratocystis ulmi, has been isolated from very old annual rings carefully dissected from numerous trees of various elm species in California. These included a 27-yr-old (1953) ring of an American elm (Ulmus americana). The fungus was isolated from rings at least 7 yr old in six different counties in the area around San Francisco Bay. However, the ability of the fungus to move laterally in a tree makes it difficult to determine how long such a tree has actually been infected.

Keyword(s):