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Incidence and Histology of Stem-Girdling Galls Caused by Fusiform Rust. C. H. Walkinshaw, Principal plant pathologist, U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, P.O. Box 2008 GMF, Gulfport, MS 39505; T. A. Roland, Technician, U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, P.O. Box 2008 GMF, Gulfport, MS 39505 Phytopathology 80:251-255. Accepted for publication 19 September 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/Phyto-80-251.

Isolates of Cronartium quercuum f. sp. fusiforme were found to produce a high incidence of lethal stem-girdling galls in certain families of slash pine. This girdling, one of many fusiform rust disease processes, was studied because it appeared to be associated with families of pines that had been selected for their putative resistance to fusiform rust. Stem-girdling galls with a bulbous swelling above a constriction on the stem were found to disorganize the tissues of rust-infected trees much more severely than typical galls tapered at both ends. Infected seedlings with stem-girdling galls grown in a greenhouse died within 1 yr; those grown in the field died after several years. Statistical differences within families and single-gall rust isolates were significant in some greenhouse experiments. Family differences were also significant for stem-girdling galls in some field plantings but not others; this inconsistent relationship was undoubtedly due to significant variation among replications.