Home Plant Health Apple Cotton Root Rot: Symptoms, Causes, and Management

Apple Cotton Root Rot: Symptoms, Causes, and Management

by Gregory
3 minutes read

What is Apple Cotton Root Rot?

Cotton root rot is a fungal disease that attacks apple trees. It is caused by a fungus called Phymatotrichum omnivorum and is most common in hot, dry climates. The fungus can also infect other plants, including pear trees, nut trees, and shade trees.

Symptoms of Apple Cotton Root Rot

The symptoms of apple cotton root rot can vary depending on the stage of the disease. In the early stages, the leaves may turn bronze or yellow and the tree may start to wilt. As the disease progresses, the leaves will turn brown and crispy and the tree may die back. One of the most distinctive symptoms of apple cotton root rot is the presence of fungal strands on the roots of affected trees.

Causes of Apple Cotton Root Rot

Apple cotton root rot is caused by the fungus Phymatotrichum omnivorum. The fungus lives in the soil and can survive for long periods of time, even in the absence of host plants. When conditions are favorable, the fungus will produce spores that can be spread by wind, water, or insects. The spores can then germinate and infect new plants.

Environmental Factors that Contribute to Apple Cotton Root Rot

Certain environmental factors can make apple trees more susceptible to cotton root rot. These factors include:

  • High temperatures: The fungus that causes cotton root rot thrives in hot, dry climates.
  • Calcareous clay loam soils: The fungus prefers soils that are high in calcium and clay.
  • Poor drainage: Soils that do not drain well can create a favorable environment for the fungus.

Management of Apple Cotton Root Rot

There is no cure for apple cotton root rot, but there are some management practices that can help to reduce the risk of infection and slow the spread of the disease. These practices include:

  • Planting resistant varieties: Some apple varieties are more resistant to cotton root rot than others. When planting new trees, choose varieties that are known to be resistant to the disease.
  • Improving soil drainage: Soils that drain well can help to reduce the risk of infection. If your soil does not drain well, you can improve drainage by adding organic matter or installing a drainage system.
  • Avoiding overwatering: Overwatering can create a favorable environment for the fungus. Water your trees deeply and infrequently, and allow the soil to dry out between waterings.
  • Mulching: Mulching around your trees can help to regulate soil temperature and moisture levels, and can also help to suppress the growth of the fungus.
  • Fungicides: Fungicides can be used to control cotton root rot, but they are not always effective. If you are considering using a fungicide, be sure to follow the label directions carefully.


Apple cotton root rot is a serious disease that can cause significant damage to apple trees. By understanding the symptoms, causes, and management practices for this disease, you can help to protect your trees and keep them healthy.

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