Cytospora Canker

Cytospora canker (Cytospora kunzei var. piceae) is one of the most damaging canker diseases of spruce trees east of the Rocky Mountains. Many species are susceptible to this disease, blue spruce is most susceptible.

Treatment Strategy

Blue spruce is often planted in stressful urban sites, which predisposes the tree to infection by the fungus. Proper cultural practices including proper irrigation, mulching, and pruning can assist with reduction of tree stress and cytospora canker infection. Cambistat can be also be used to promote tree health and has been shown to significantly reduce cytospora infections.

Cambistat has fungistatic properties that have a direct mode of action on fungal diseases, and Cambistat improves the health of trees, which improves their ability to withstand stress induced diseases. For best results, Cambistat should be applied as part of an overall management strategy aimed at improving tree health. There are no other chemical control options for cytospora.

Other Treatment Practices

  • Prune heavily infected branches during dry periods in the growing season, or in late winter.
  • Prune six to twelve inches beyond the canker.
  • Remove infected trees away from healthy trees.
  • Apply Cambistat when the soil is not frozen or saturated.
  • Also include cultural practices to promote tree health such as proper irrigation, mulch, and correcting soil conditions.

Soil Drench/Injection Using Cambistat

Expected Results

A single Cambistat application provided two years of prevention of Cytospora canker in a trial conducted by The Morton Arboretum. When compared to untreated spruce, Cambistat significantly reduced the development of Cytospora at the label rate of Cambistat. Cambistat will not cure this disease if cankers are present at the time of application, however, it will prevent the development of further infection. Use Cambistat as a tool in combination with other tree health care treatments that promote overall tree health.

There are numerous reasons for Cambistat’s ability to reduce the incidence and severity of cytospora.

  • Cambistat has fungistatic properties that have a direct mode of action on fungal diseases.
  • Cambistat also has been shown to alter the leaf surface of treated trees making them less susceptible to penetration by fungal propagules.
  • Cambistat improves the health of spruce trees which improves their ability to withstand stress induced diseases such as Cytospora.

Cambsitat has also been shown to reduce the severity of needlecasts on spruce as well.

For best results, Cambistat should be applied as part of an overall management strategy for these diseases including traditional fungicide spray applications for Rhizospharea.

Cambistat treatments result in only moderate growth regulation of spruce (30-40%) which can also be desirable in areas where growth reduction is needed.

Signs of Damage

  • Browning of entire limbs, starting low in the canopy moving upwards over time
  • Dieback of entire limbs, can be seen year round
  • White/blue sap oozing from infected branch lesions near the trunk, seen year round
  • Very small fruiting bodies are extremely difficult to find near the margins of branch lesions

Trees At Risk

  • Blue spruce (Picea pungens)


  • The fungus enters through wounds on branches caused by insects or heavy snow loads.
  • The next spring the fungus produces orange reproductive structures.
  • Throughout the growing season water, birds, insects, or humans move the fungus from the reproductive structures to new infection sites.


Jacobs, K. A., & Berg, L. C. (2000). Inhibition of fungal pathogens of woody plants by the plant growth regulator paclobutrazol. Pest Management Science, 407-412.

Watson, G., & Jacobs, K. (2012). Control of Apple Scab and Cytospora Canker with Paclobutrazol. Arboriculture & Urban Forestry, 112-116.

Chorbadjian, R. A., Bonello, P., & Herms, D. A. (2011). Effect of the Growth Regulator Paclobutrazol and Fertilization on Defensive Chemistry and Herbivore Resistance of Austrian Pine and Paper Birch. Arboriculture & Urban Forestry, 278-287.

Zhang, P. G., Sutton, J. C., & Fletcher, R. A. (1994). Paclotbutrazol protects black spruce seedlings against predisposition to gray mold induced by high temperature and drought. Canadian Journal of Forest Resources, 1033-1038.

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