Question:
My 'Spring Snow' crabapple bloomed beautifully this spring, but has recently begun to lose many of its leaves. Why?Answer:
The ‘Spring Snow’ crabapple is widely planted as it’s one of the few crabapple varieties that doesn’t bear fruit. Unfortunately, ‘Spring Snow’ is very susceptible to apple scab.
Apple scab is a fungal disease. It’s caused by the fungus Venturia inaequalis. Cool, wet weather in spring favors apple scab development.
Apple scab appears as velvety, olive-green to black spots on the 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. Heavily defoliated crabapples are not very attractive.
Apple scab can be prevented by applying fungicides from bud break through mid-June. Sanitation also plays a role in controlling apple scab. Raking and destroying the leaves as soon as they fall should help reduce the severity of the infection next season. However, the best way to prevent apple scab is to plant scab resistant crabapple varieties.