Diseases of the Horse Chestnut Tree

The horse chestnut tree (Aesculus hippocastanum) naturally occurs in the Balkans, but typically performs well in United States Department of Agriculture (USDA) Hardiness Zones 3 to 8. This large member of the Hippocastanaceae plant family reaches up to 75 feet in height with spreads up to 65 feet. Horse chestnut trees often suffer from common plant diseases.

Leaf Blotch

Leaf blotch of horse chestnut, a fungal disease caused by the Guignardia aesculi pathogens, often affect horse chestnut trees that are younger than 5 years of age. Early symptoms typically include small, water-soaked lesions forming on the leaves. These sores often enlarge and merge until the entire leaf turns brown. Infected leaves generally curl and fall off the branch. The fungal pathogens overwinter in infected leaves and then germinate during wet spring weather. Preventative measures include raking up and discarding any fallen leaves each autumn.

Anthracnose

Powdery mildew, a disease triggered by the Uncinula flexuosa fungus, appears as a dirty white to dark gray coating that covers the horse chestnut leaves. Initial signs include small, white spots forming on the leaves. These spots expand and merge until a mat of mildew covers the affected leaves. Powdery mildew can also cause distorted, stunted or yellowed leaves. Severely infected horse chestnut trees suffer from premature leaf drop. Because the fungal pathogens draw nutrients from the horse chestnut, this infection frequently causes the tree to lose vigor and its overall health to decline. Powdery mildew symptoms typically appear late in the growing season after extended periods of wet weather. Preventative measures include planting the trees far enough apart to allow for proper air circulation. Control includes applying fungicide and removing infected foliage.

Powdery Mildew

Powdery mildew, a disease triggered by the Uncinula flexuosa fungus, appears as a dirty white to dark gray coating that covers the leaves. Initial signs include small, white spots forming on the leaves. These spots expand and merge until a mat of mildew covers the affected leaves. Powdery mildew can also cause distorted, stunted or yellowed leaves. Severely infected horse chestnut trees suffer from premature leaf drop. Because the fungal pathogens draw nutrients from the tree, this infection frequently causes the tree to lose vigor. Powdery mildew symptoms typically appear late in the growing season after extended periods of wet weather. Preventative measures include planting the trees far enough apart to allow for proper air circulation. Control includes applying fungicide and removing infected foliage.

Bleeding Canker

Bleeding canker of horse chestnut, a bacterial disease caused by the Pseudomonas syringae pathogens, commonly infects horse chestnut trees growing in the United Kingdom (U.K.). Early signs of this disease include the formation of lesions that ooze a rust-red liquid that looks similar to blood. The tissues around the lesions often crack, and fungal growths develop in the dead bark. Chronic bleeding canker infections can cause yellow foliage, stunted leaf growth and crown death. No preventative or control measures currently exist.

Keywords: horse chestnut diseases, horse chestnut problems, horse chestnut trees

About this Author

Cat Carson has been a writer, editor and researcher for the past decade. She has professional experience in a variety of media, including the Internet, newspapers, newsletters and magazines. Her work has appeared on websites like eHow.com and GardenGuides.com, among others. Carson holds a master’s degrees in writing and cultural anthropology, and is currently working on her doctoral degree in psychology.