Tropical storm Lee brought us rainfall that totaled 2.72 inches over several days, Sept. 4-7. The ground seemed to soak up this volume of rain surprisingly well, and it will be beneficial for sizing the apple crop. Of course this amount of rain and the extended wetting should be expected to have some consequences for disease development, particularly if fungicide residues were low. Keep watching for sooty blotch and flyspeck, as well for as fruit rots such as bitter rot.
For the record, we had extended wetting periods of 16 hr Sept 4-5 at 69º F, 47 hr Sept 5-7 at 69º F, 12 hr at 64º F Sept 7-8 with Lee, and a more recent one of 22 hr at 68º degrees. Generally, wetting in the higher temperature ranges favor more rapid rot infection and development, and ripening fruit are more susceptible to infection. Typically, residues of a protectant fungicide such as captan do not weather through more than two inches of rainfall in a one week period.
Disease management information directed mostly to the Frederick County Virginia tree fruit industry, updated as needed throughout the growing season. Keith Yoder, Virginia Tech Agricultural Research and Extension Center, Winchester, Virginia
About Me
- Keith Yoder
- Professor Emeritus of Plant Pathology, Virginia Tech Ag. Research and Extension Center, Winchester, VA
