| Figure 1. ‘Golden Delicious’ apple leaves showing leaf blotch and yellowing associated with NLB. Photo: T. B. Sutton, North Carolina State University, and A. L. Jones, Michigan State University. |
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Necrotic leaf blotch (NLB) is a physiological disorder whose occurrence is related to air temperature, light intensity, and soil moisture. The cause of NLB of apple is not known. Symptoms that are enhanced by gibberellins and reduced by abscisic acid are evidence that a hormonal imbalance may be involved. The disorder …