Leopold Center
U.S. Department of Agriculture



Recent research at North Carolina State University and University of Kentucky led to development of a sooty blotch/flyspeck warning system. This system advises growers to apply their second-cover fungicide spray after 175 hours of wetness have been measured since the first-cover fungicide spray was applied. In contrast, the conventional practice is to apply the second-cover spray 10 to 14 days after the first-cover spray.

Using a weather datalogger in your orchard or SkyBit remotely sensed data, you start counting wet hours (due to rainfall or dew) from the time you apply the first-cover fungicide spray. Wetting periods less than 4 hours long are not counted in the 175-hour total. Simply add up the hours in wet periods 4 hours or more long, day by day, until you reach a total of 175 hours; then it’s time to apply the second-cover fungicide spray. This spray should include a benzimidazole fungicide (either Topsin-M or Benlate; remember that Benlate will not be sold after January 2002). After the second-cover spray is applied, you should return to a protectant cover-spray fungicide program for the remainder of the season.
Click here for more information on the ISU Horticulture Farm Trials.
Click here for more information on the Cooperating Grower Trials.

Email: mgleason@iastate.edu Telephone: (515) 294 0579 Address: 312 Bessey Hall, Iowa State University, Ames IA 50011