Beech Canker Diagnostic Guide

Bleeding canker in Beech is caused by Phytophthora spp., a well-known genus of fungi capable of causing serious damage in many hosts. In the case of Beech, it can cause root rot as well as trunk and branch cankers. Cankers form, coalesce and eventually weep a reddish fluid which stains the bark. As cankers girdle the trunk the crown thins, dies back, and can become chlorotic. Field diagnosis can be difficult and often requires lab analysis.

All beech species are susceptible to beech canker. In the US, American beech, Fvagus grandifolia, is the most commonly affected.

American Beech

Signs of Damage

Beech Canker Signs
Beech Canker Signs

Bleeding cankers on the bark of a beech tree

  • Cankers and rot are the most common symptoms of this disease.
  • Cankers can appear dark in color, sunken, weeping, or any combination thereof.
  • Root rot is less-obvious to the casual observer, but exists both in overly wet and seemingly-normal conditions. This is often where infection begins in trees.

Physical Appearance

None without magnification.


The life cycle is complicated and not particularly important to the diagnosis and treatment of this disease. Even after host trees have died Phytophthora spp. are capable of surviving for months until conditions are appropriate for growth. Thus, many life stages are present in infected settings. Multiple species of the fungus often inhabit the same site. On its own, phytophthora spp. spores can only move several centimeters while swimming with flagella. With flowing water as a vehicle though, the spores are capable of moving much larger distances.

Treatment Strategy

Prevention of the disease is the surest control. Beech canker thrives in water-logged areas. It often begins in roots and moves upward into the tree’s trunk. Wounding of the bark creates avenues for infection. Agri-fos is the only fungicide known to mitigate this disease, though Subdue Maxx may provide minimal control.

Other Treatment Practices

  • Preventing beech canker through cultural practices can save trees.
  • Air spading, mulching/RES, and proper watering can prevent infections from beginning. This can also help trees defend against the fungus once they are infected.
  • Cambistat can help trees recover from stress. Along with the above cultural practices and Agri-fos, Cambistat can help trees regrow fine roots, increase leaf thickness, and increase tricome leaf hairs.
  • Subdue Maxx (mefenoxam) has been shown to aid in control, but should not be used as a stand-alone treatment.
  • Beech canker can also be associated with beech wooly aphid. Application of Xytect can control this insect.
  • Systemic Bark Spray using Agri-Fos Plus

    Notes: Combined with Scrimmage
    Dosage: 40.5oz/62.4 oz water
    Timing: Anytime during growing season.
    Re-Treatment: Every 8-12 weeks
    Agri-Fos Plus
    Agri-Fos Plus Login for pricing
  • Systemic Bark Spray using Scrimmage

    Notes: Combined with Agri-Fos
    Dosage: 3.2 oz/62.4 oz water
    Timing: Anytime during growing season.
    Re-Treatment: Every 8-12 weeks
    Scrimmage Nonionic and Organosilicone Surfactant Blend
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Treatment Expectations

Phytophthora is a fungus capable of enormous damage. While Agri-fos has been shown to be efficacious against stem cankers, infections can occur elsewhere. Phytophthora is ever-present in the soil, which is why cultural practices are so important.

A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy Use of the images does not imply endorsement of treatments by

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