VIEW ARTICLE

Ecology and Epidemiology

Persistence of Chlamydospores of Fusarium culmorum in Wheat Field Soils of Eastern Washington. D. A. Inglis, Former research assistant, Department of Plant Pathology, USDA, Agricultural Research Service, Washington State University, Pullman 99164, First author is presently IPM Coordinator at Montana State University, Bozeman 59717; R. J. Cook, research plant pathologist, USDA, Agricultural Research Service, Washington State University, Pullman 99164. Phytopathology 76:1205-1208. Accepted for publication 8 April 1986. 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, 1986. DOI: 10.1094/Phyto-76-1205.

Chlamydospores of Fusarium culmorum occurred in wheat field soils of eastern Washington nine times more frequently as endoconidial types than as mycelial types. Endoconidial chlamydospores survived slightly better in Palouse silt loam soil at Pullman, WA, than in Ritzville silt loam soil at Lind, WA, over a 3-yr study. Slope values of the survival curves (percentage of surviving propagules over time) obtained by using the log-probit transformation were -3.41 and -1.41 for Lind and Pullman, respectively. LD₅₀ values (time when 50% of the propagules were dead), interpolated from the transformed curves, were 208 and 267 days for Lind and Pullman, respectively. TS₅₀ values (time when 50% of the propagules survived), estimated directly from arithmetic plots, were 215 and 330 days for Lind and Pullman, respectively. Despite the ability of the fungus to survive slightly longer in field soil at Pullman than at Lind, field survey data have consistently demonstrated a higher frequency of infested fields in the Lind than in the Pullman area. Plant water stress is required for disease development and is common in the Lind area (25 cm annual precipitation) but is rare near Pullman (53 cm annual precipitation). Because the relatively lower incidence of infested fields in the Pullman area cannot be explained by the inability of the fungus to survive as chlamydospores in the soil, it apparently relates to environmental conditions that are unfavorable for disease development or the production of new chlamydospores.