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Keeping Flowering Crabapples Beautiful

Source: NDSU Extension Service Horticulturists

In recent years homeowners have found the flowering crab an irresistible ornamental tree. Whatever the season, flowering crabs lend color and interest to our landscape. Spring flowers, summer foliage, fall fruits, and winter branch pattern and bark color create year-round interest.

However, flowering crabs often turn unsightly as spring fades into summer and foliage becomes blighted with a common fungus disease called scab. Infected leaves may remain green or turn yellow, gray, or black. 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. Some fungicide use may be required to adequately protect susceptible crabs in wet seasons. If you choose to apply a fungicide for scab control, begin applying it in early spring as the leaves emerge. Three applications are usually sufficient.

If you have further questions, please contact your county office of the NDSU Extension Service.

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