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Relation of Site Factors to Fusiform Rust Incidence in Young Slash and Loblolly Pine Plantations in the Coastal Plain of Florida and Georgia. Robert A. Schmidt, Professor of Forest Pathology, Department of Forestry, School of Forest Resources and Conservation, Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32611. Thomas Miller, Renee C. Holley, Roger P. Belanger, and James E. Allen. Research Plant Pathologist, USDA Forest Service, Southeastern Forest Experiment Station; Statistician I, Department of Forestry; Research Silviculturist, USDA Forest Service, Southeastern Forest Experiment Station; and Assistant in Forest Pest Management, School of Forest Resources and Conservation, Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32611. Plant Dis. 72:710-714. Accepted for publication 25 March 1988. 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, 1988. DOI: 10.1094/PD-72-0710.

The relation of soil drainage, soil surface texture, site preparation methods, and site index to the incidence of fusiform rust, caused by Cronartium quercuum f. sp. fusiforme, was examined in more than 1,200 slash pine and 230 loblolly pine plantations in eight forest management areas of the Florida and Georgia coastal plain. Rust incidence was the percentage of living trees at age 56 years with at least one stem or branch gall. In a combined analysis of all management areas, rust incidence in both pine species was greatest on sites with well- or moderately well-drained soils with loamy sand or sandy loam surface texture and least on sites with poorly or somewhat poorly drained soils with a sandy surface texture. Individually, some management areas exhibited the same overall trend, but in other areas, especially high rust incidence areas, plantations had high rust incidence regardless of soil drainage or texture class. Old field sites had significantly greater rust incidence, which appears to be the consequence of these sites being located on the better-drained loamy soils. Regionwide, an estimated site index based on soil characteristics was negatively correlated with rust incidence in both pine species. This unexpected trend resulted because of the dependence of the site index system on soil drainage and texture. Within soil drainage/texture classes, the site index was positively correlated with rust incidence in slash pine. These forest inventory data are correlative and do not establish cause and effect. Nevertheless, they aid our understanding of fusiform rust distribution and management. A definitive rust hazard model at the stand level will require quantitative data on alternate host (oak) abundance and dispersal of inoculum.

Keyword(s): disease hazard, disease management, epidemiology, Pinus elliottii var. elliottii, P. taeda.