Identifying and Treating Chestnut Tree Diseases

Chestnuts are sturdy, pest-resistant trees and very few chestnut diseases can cause large-scale damage. Chestnut trees, part of the Castanea family, require little maintenance, pruning or fertilization. However, some weather conditions can make chestnuts vulnerable to fungal infections. These diseases are easy to detect, but can be hard to contain. You should know how to identify such diseases in their initial stage and prevent them from spreading.

Disease 1 - Chestnut Blight Disease

This is the most destructive of all known, chestnut diseases. There are no easy methods to cure a chestnut blight infection and most affected chestnuts eventually die. Also called the Bark Disease, it is caused by the Cryphonectria fungus. The fungus enters the tree’s bark through wounded sites on the bark’s surface.

Chestnut Blight Symptoms

The fungus causes quick deterioration in the overall health of the bark. Due to widespread tissue infection, small canker-like sores develop on the bark. The younger stems start thinning and branching, excessively. Small sprout-like bodies can be seen around the cankers. Within weeks of infection, the bark appears shrunk. The tree may even appear bent due to rapid loss of tissue from one side of the bark. Cankers caused by fungal infection often become the nesting ground for the Bark Miner. This insect usually doesn't attack healthy chestnuts but in diseased trees, it multiplies quickly. The presence of miner means intensive feeding and creation of more bruised sites on the bark. This further helps the spread of fungal infection among the upper branches of the tree.

Chestnut Blight Control

No effective form of organic or chemical control is known that can completely cure blight-affected chestnut trees. Most advocated treatments are very expensive and include the use of complex, scientific techniques. Therefore, making your chestnuts immune against blight infestation through the following two-fold strategy is recommended:

Planting Precaution

Before planting a chestnut, make some enquiries in your area. If the surrounding landscape has a history of chestnut blight infections, you should grow the Asiatic varieties, like Chinese chestnut. This chestnut is more resistant against fungal infections. When procuring a chestnut plant, ensure that you ask for a certificate from the seller stating that the plant is free of blight-causing pathogens. Most reputed garden supply stores issue such certificates. 

Pruning Precaution

You should guard against bruising the main bark. Never use heavy pruning shears for pruning chestnuts. Before pruning, dip your cutting equipment in an anti-fungal preparation. While pruning, ensure that you keep away from the main bark area. After pruning, check for wounded sites. Any kind of cut marks on the bark should be immediately sprayed with an all-purpose fungicide.

Oak Mildew

Oak mildew is the more serious form of powdery mildew that is commonly found in household gardens. It is also called the Chestnut Powdery Mildew. It is caused by the Sphaerotheca fungus.

Oak Mildew Symptoms

This disease is more common among the younger chestnuts. The shoots develop a dwarfed appearance. The tree becomes more sensitive to colder temperatures. The fungus is more developed along the upper half of leaves. The leaves develop a typical, white-colored, coated appearance. However, this coating can be seen during the summer season only.

Oak Mildew Control

Any part of the tree showing symptoms of mildew should be pruned-off. Chemical control is best suited for treating this disease. You can use any retailed fungicide that has sulphur and benomyl in the listed formulation. Repeated fungicide spraying is both curative and preventive. You should prune-off, curled-up branches to create entry points for air. Increased ventilation in the foliage helps to limit the spread of mildew.