Necrotic leaf blotch

Disease

Necrotic leaf blotch

Physiological disorder

Distribution: This is a physiological disorder affecting only Golden Delicious and its bud sports.


Medium to large, irregular necrotic lesions occur on the foliage of mature leaves during mid- to late summer. The remaining green tissue generally turns yellow shortly after the appearance of symptoms (A, B). The onset of symptoms is often sudden and occurs in 2 to 4 waves during the summer. Defoliation rapidly follows the onset of symptoms and may affect fruit quality if it is extensive.

  • Crops Affected: Apples

    Management

    Necrotic leaf blotch is caused by the rapid synthesis of gibberellins triggered by environmental factors. Treating trees with zinc-containing fungicides (e.g., Ziram) or foliar sprays containing zinc nutrients can decrease the severity of necrotic leaf blotch. Zinc oxide applied every 2 weeks from budbreak to harvest can diminish symptoms.

    Similar Species

    This disorder can be confused with Magnesium deficiency (C).