Seasonal variations in populations of Fusarium species in wheat-field soil

Populations in soil of the fungus Fusarium culmorum, a cause of brown foot rot in wheat, and of other Fusarium spp. were monitored in two successive crops of autumn-sown wheat on each of three sites. The occurrence of fluctuations in populations, within and between crop-growing seasons, was confirmed. Smaller populations of F. culmorum occurred on the site that had not grown a cereal crop in the previous year. There was usually a decrease in F. culmorum in late autumn or early winter as temperature decreased and soil moisture increased. Its populations then increased in spring or summer, sometimes following rainfall, but with variations among sites in amount and timing. Conditions in each year were unsuitable for the development of brown foot rot or for rapid increases in populations of F. culmorum as foot rot developed. This led to populations that were generally smaller in the second year. The significance of these fluctuations for the development of disease on wheat from inoculum in the soil is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.