During spring these two diseases may infect disease prone plants. Cool, wet weather in spring creates ideal conditions for the fungal disease apple scab.
Apple scab affects susceptible apples and ornamental crabapples.
Leaves on severely infected trees develop gray blotches, turn yellow and drop in midsummer. Apple scab will also affect flowers, fruits, and in rare cases twigs. Apple scab does not permanently damage a tree. However, severe defoliation two or three successive years can weaken a tree to the point that it becomes prone to winter or drought injury. Reduce the chance of apple scab infection with the following practices.