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First Apple Scab Symptoms at Penn State FREC Observed May 2

Posted: May 4, 2011

The first scab symptoms at the Penn State Fruit Research and Extension Center in Biglerville were observed May 2 on Rome Beauty. Based on the New Mills Apple Scab Disease Model, apple scab infection periods occurred April 1, 3-4, 10-13, 16-17, 19-20, 22-24, 28 and May 2-3. As a result of the extended wetting periods, growers who have not used a DMI fungicide on apples this season should consider using one at bloom or petal fall. Due to moderate resistance to these products, be sure to use the higher rates allowed on the label.

In orchards where a straight protectant program (mancozeb and/or captan) has been used, there could be some early infections. The frequent and extended wetting periods are also excellent conditions for cedar apple rust and quince rust infections. Application of a DMI (including Inspire Super, Rally, Vintage, Indar or Procure) between pink and petal fall will help clean up scab lesions before they begin sporulating if scab is not already resistant to these materials in your orchard. Modified from: Cornell Cooperative Extension Hudson Valley Regional Fruit Program, Tree Fruit Recorded Message for Tuesday, May 3, 2011