Apple Physiological Disorder - Necrotic Leaf Blotch

The cause of necrotic leaf blotch of apple is not known, and it is considered a physiological disorder. The disorder is most common on Golden Delicious worldwide.
Apple Physiological Disorder - Necrotic Leaf Blotch - Articles

Updated: November 14, 2017

Apple Physiological Disorder - Necrotic Leaf Blotch

The disorder is characterized by irregularly shaped necrotic blotches on the leaves, limited by the veins. Affected leaves turn yellow in about 4 days and subsequently fall off the tree. Photo by K. Peter.

Symptoms

The disorder is characterized by irregularly shaped necrotic blotches on the leaves, limited by the veins. Necrotic areas can range in size and midshoot leaves are most affected. Affected leaves turn yellow in about 4 days and subsequently fall off the tree. Other characteristics of the disorder are 1) the symptoms develop suddenly, appearing overnight and 2) can occur in waves from July through August.

The disorder tends to be more common and severe later in the summer; however, usually appearing when a cool, rainy period is followed by hot summer weather. Some orchards or trees within an orchard may show little or no defoliation, while other orchards or trees reach 50 percent defoliation or more.

Management

Although no bacteria or fungi have been associated with the necrotic leaf blotch, the disorder has been reduced where the dithiocarbamate (EBDC) fungicides ziram or thiram are used in the summer spray program. Foliar applications of zinc oxide also have been effective in reducing the severity of the disorder.

Authors

Apple and pear diseases Peach, cherry, other stone fruit diseases Tree fruit disease management

More by Kari A. Peter, Ph.D.