Apple Scab and Your Crabapple Trees
Apple scab (Venturia inaequalis), is one of the most common and serious fungal diseases of flowering crabapples in Minnesota. Symptoms appear as olive-colored spots on leaves and are first seen in late May and early June. As the disease progresses into June and July, leaves yellow and begin to fall, causing crabapples to become thin. Consecutive days of cool, wet weather in April and May when leaves are immature lead to new infections.
Crabapples infected with apple scab are weakened and stressed due to the leaf loss and can be prone to more serious problems. Spraying crabapples preventatively as new leaves emerge and fertilizing on an annual basis are the best method of controlling and minimizing the impact of apple scab.
Here’s what we can do
Shadywood Tree Experts can help maintain your trees with the use of systemic and/or contact fungicide spray applications and annual fertilization. When you sign up for plant health care from Shadywood, we administer the recommended protocols for disease prevention control to keep your trees healthy. With each visit, our arborists assess trees for overall health.
Additional things you can do to maintain the health of your crabapple tree
Water trees regularly using a hose or small sprinkler for at least an hour once every one to two weeks if we do not receive adequate rain. Avoid spraying leaves directly when watering as wet leaves can promote fungal diseases. Mulch root systems when possible, using natural wood chips to protect the trunk, condition and improve the soil, and to conserve soil moisture. Rake up and dispose of fallen diseased leaves. If you see anything that doesn’t look right, have your trees inspected by one of Shadywood Tree Experts International Society of Arboriculture Certified Arborists.
Apple scab has caused this crabapple tree to appear thin and unhealthy.
Apple scab infected leaf
Constantly spraying leaves with irrigation can cause apple scab to become worse. We have been treating the crabapple trees at this property and asked the home owner if they can have their sprinklers adjusted to avoid spraying leaves.