Silver leaf disease

After two cold winters silver leaf disease has reared its head across the province this year. While this pest is not typically a large concern in Ontario apple orchards, there have been reports of it appearing in different areas across Ontario. The first symptoms appear after petal fall, with leaves appearing silver in colour as the name suggests (Figure 1).

Initial symptoms include one or two branches with silvering leaves, and the silvering can eventually spread through the entire tree. Symptoms can get worse over a number of years until the tree eventually dies. However, symptoms can also stop progressing and the limbs can even recover completely, leaving the tree in good health. Growers should keep an eye on the infected limbs to determine if action is necessary.

The heartwood of infected trees is usually stained brown, and fruiting bodies can appear in the fall on the surface of dead or infected limbs or trunk. Infections of silver leaf occurs through wounds or dead tissue. As it is an opportunistic fungi, it enters trees through previously damaged wood, either by winter damage, physical damage, or other pests and diseases. Pruning cuts are also susceptible to infections from spores during rainy weather.

Silver leaf disease can easily be confused with powdery mildew. However, powdery mildew appears at the growing tips of shoots as white, felt-like patches of fungal growth, while silver leaf appears more as a silver sheen on mature leaves.

There are no fungicide options to control silver leaf. To manage the disease prune out the infected branches and keep trees in good health. Keep an eye on the affected limbs as they may recover. If action is necessary make the pruning cuts below the damaged area into healthy tissue. To reduce the risk of infection keep your trees free of stress and provide adequate drainage and fertilization to reduce the incidence of disease.

Silver leaf disease

Silver leaf disease

There are no fungicide options to control silver leaf. To manage the disease prune out the infected branches and keep trees in good health. Keep an eye on the affected limbs as they may recover. If action is necessary make the pruning cuts below the damaged area into healthy tissue. To reduce the risk of infection keep your trees free of stress and provide adequate drainage and fertilization to reduce the incidence of disease.

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