Tree Diseases

Anthracnose

Anthracnose is a common disease among deciduous trees, especially sycamore, ash and oak. It also affects shrubs such as privet. The disease is more prevalent during wet, cold springs. It is not a serious tree health threat and doesn’t normally require treatment. To prevent anthracnose fungi dispose of leaves and twigs, as well as increasing air circulation by pruning infected twigs and branches when the tree is dormant.

Apple Scab

Apple scab is a common disease of apple trees and crab apple trees, as well as mountain ash and pear. It’s caused by a fungus that infects leaves and fruit, leaving the latter unsuitable for eating. It’s best to plant a variety that is resistant to apple scab. You can minimize apple scab by raking and disposing of leaves before winter.

Canker Diseases

A variety of canker diseases affect trees, including Cytospora canker on pine, poplars, spruce and willows. These diseases result when a fungal or bacterial pathogen enters bark or sapwood through a wound. The vascular system becomes blocked and nutrients cannot flow. This blockage can cause branches to die. Preventive measures include growing trees suited to the available space and conditions to avoid injury to bark. Proper maintenance, winter protection, and removing any branches affected by canker is a solution.

Dothistroma Needle Blight

This blight causes pine needles to turn brown at the tips. Slowly, the entire needle turns brown and falls off. Dothistroma needle blight can be fatal and is most common with Austrian pine and Ponderosa pine. Preventive measures include ensuring good air circulation by avoiding crowding, as well as mulching trees and watering them at the base to avoid wetting foliage.

Oak Wilt

Oak wilt is a fungal disease caused by the organism Bretziella fagacearam. The disease is limited to the Midwestern and Eastern United States. Once the trees are infected the tree will die. There is no treatment other than removing infected trees.

Powdery Mildew

Powdery mildew is easy to spot due to the powdery white coating covering foliage. Caused by a fungus, it is most often found on plants in shady areas, particularly when there’s a lot of humidity but no rain. To control, avoid planting plants auch as crape myrtle and lilac. Choose resistant varieties instead. Give existing plants good air circulation as well.

Phytophthora Root Rot

Phytophthora root rot is a fungal disease that attacks trees growing on poorly drained sites. Although there are no treatments for root rot, there are things you can do to prevent it. Avoid planting trees in wet areas or near downspouts. Never plant trees deeper than they grew at the nursery and avoid piling soil against the trunk.