Crabapple tree diseases. Cures?
Leaves have brown spots turn yellow and fall off..what can be done...
Hamilton County Iowa
The leaf drop may be due to apple scab. Apple scab is a fungal disease caused by the fungus Venturia inaequalis. Cool, wet weather in spring favors apple scab development. Crabapple varieties differ in their susceptibility to apple scab. Some varieties are very susceptible to the disease, while others are resistant to apple scab.
Apple scab appears as velvety, olive-green to black spots on crabapple leaves. Heavily infected leaves turn yellow and fall from the tree. Highly susceptible crabapple varieties may lose a large percentage of their leaves by mid-summer. Fortunately, apple scab does not kill affected trees. The damage is mainly aesthetic.
The best way to prevent apple scab is to plant scab-resistant crabapple varieties.