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Apple Scab Fungus

The first symptoms of Apple Scab Fungus are small, irregular-sized light-brown to olive-green spots on the underside of leaves. As the fungus progresses, the lesions become larger, more round and a velvety olive-green or black color. The infected leaves begin to curl and appear scorched on the edges. The upper side of the infected leaves bulge and the underside sinks inward. As the fungus spreads, the infected leaves turn yellow and drop early in the season. The overall appearance of the tree is less attractive and the health of the tree is compromised. The most commonly affected tree varieties are Crabapples and Apple trees. Click here for more information on Rust diseases common to the Chicago area.

Treatment timing is very important when battling Apple Scab Fungus. Once the fungus has developed and spread throughout the tree, it may be too late to treat during the current growing season. Furthermore, the fungal spores do not die during the winter. Instead, they overwinter in bark crevices and on fallen leaves. During the spring, millions of fungal spores are released into the air and carried by the wind to infect new leaves.  Moderate temperatures and wet conditions are ideal for the spread of Apple Scab fungal spores. It’s vital that treatment begins when leaf buds begin to break and continues until the tree’s flower petals fall. In our region, leaf bud break is typically mid-April, but every year varies. Kramer Tree Specialists offers a variety of treatment options, including a series of three fungicide spray applications that begin at leaf bud break and continues through the tree’s most vulnerable stages. The Plant Health Care Department at KTS carefully monitors weather conditions to ensure the applications begin at the appropriate time for optimal effectiveness.

Apple Scab Fungus is most prevalent in moist conditions, created by either rainfall or irrigation. In addition, stressed or unhealthy trees are more vulnerable to an attack. It’s important to address any other concerns the tree may have. For example, fertilization may be vital to improving the overall health of the tree. This enables the tree to fight off many disease and pest attacks by creating a healthy barrier. General yard maintenance helps inhibit the growth of the Apple Scab Fungus. It’s important to remove infected, fallen leaves and twigs from the landscape. Doing this slows the spread of the Apple Scab fungal spores. Unfortunately, there is no cure for Apple Scab Fungus, but utilizing a combination of fungicides and proper yard sanitation is effective in controlling the fungus.

Due to the droughts our area has experienced recently, many local trees are stressed and more vulnerable to disease and insect problems this year. Contact the Plant Health Care Department at KTS to discuss how our treatments can assist in the landscape. Kramer Tree Specialists has Certified Arborists available who will visit your property to properly diagnose and provide treatment options for your trees and shrubs.

It’s not too late to treat for Apple Scab Fungus this year. Applications will begin in the next few weeks. If you have received a proposal from one of our Certified Arborists, call today to get on the schedule!

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