Apple Scab Spores Begin To Emerge In Pennsylvania

By Growing Produce Staff|April 14, 2015

In the latest tree fruit disease update, Kari Peter of Penn State University Extension notes apple scab spores have begun their release from overwintering leaves. Although Peter says only a few spores have been detected at the Fruit Research and Extension Center in Biglerville, PA, she suspects the population will climb until its peak at petal fall.

“It’s a good idea to apply copper to your trees to help knock back the population of any overwintering scab spores. Copper will also help knock back the bacteria causing fire blight, bacterial spot, as well as the spores from other fungal diseases,” she writes. “For apple cultivars at green tip or beyond, consider applying a broad spectrum (mancozeb, captan), or Syllit (dodine) plus mancozeb or captan right now.”

Peter also expects peach leaf curl to be a problem this year, with cooler temperatures in the spring.

“Disease incidence is the greatest when rains wash overwintered spores into the bud and cool temperatures lengthen the time that the emerging leaves are exposed to the pathogen, before they are fully expanded and can resist penetration by the fungus,” she writes.

Peter recommends applying a fungicide to trees prior to bud swell.