Weather and Small Grain Diseases

Most small grain diseases, especially those caused by pathogenic fungi, are favored by wet weather - either rainfall, dew periods, or high relative humidity.  Pathogen growth is favored further by accompanying moderate temperatures, usually between 60 and 85 F.

Particular diseases have their own requirements within these wetness and temperature limits.  The tan spot fungus needs a minimum of 5 hours of wetness, for example, for infection of wheat leaves.  See the web pages that discuss the individual diseases for more information.

One reason for giving these weather summaries is to allow users to adjust the forecasts that may be given for a site some distance away from their field.  Rainfall is especially variable over short distances.  Keep in mind that the effect of rainfall amount may be felt for several days afterwards in the form of dew periods and higher relative humidity.

Source: NDSU Small Grains Plant Pathology program