Infected leaves drop early, leaving a sparse tree well into fall. The disease seldom kills trees. Most older varieties of crabs, such as Hopa, are susceptible to the scab disease. During dry years, little scab prevails. Wet seasons may bring epidemics.
Many new varieties are less prone to scab.
To avoid scab problems, select one of these. Ornamental crabs that are fairly isolated from other susceptible crabs, hawthornes, or apples benefit from thorough cleanup of diseased leaves. For best results, rake and discard leaves in fall when the trees become bare. This destroys the source of early spring infection. Sanitation is more useful in dry years than wet years, but in many situations it may replace early season fungicide applications.