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Apple Scab Infections to Date

Posted: March 29, 2012

Actual and predicted apple scab infections for Penn State FREC, based on the Campbell Scientific Weather Data System and the New Mills Apple Scab Disease Model, are now posted.
Dr. Noemi Halbrendt, Penn State Fruit Research and Extension Center, Plant Pathology Associate

Dr. Noemi Halbrendt, Penn State Fruit Research and Extension Center, Plant Pathology Associate

The first infections often occur on the leaves surrounding flower buds. Dull, olive green areas visible on the undersides of leaves are the first evidence of the disease. As the lesions (infected areas) become older, they assume a definite outline as olive-green or brown circular spots. Leaves are susceptible to infection for about 5 days after they unfold. Severe early leaf infection can result in dwarfed, twisted leaves, which may drop later in the season. Early infection may occur on the calyx (blossom end of the fruit) or on the pedicel (fruit stem). Severe pedicel infection results in fruit drop. Fruit may become infected at any time in its development.