Cytospora Canker Diagnostic Guide
Cytospora canker (Cytospora kunzei var. piceae) is one of the most damaging bark diseases of spruce trees east of the Rocky Mountains. Many species are susceptible to this disease, but for the purposes of this protocol, cytospora on blue spruce (Picea pungens) will be discussed. Blue spruce is often sited incorrectly causing stress, which predisposes the tree to infection by the fungus. Cytospora rarely kills trees outright, but it makes them unsightly by killing branches and causing sap ooze from infected branch lesions.
Trees at Risk
Cytospora canker is one of the most damaging diseases of spruce trees east of the Rocky Mountains. Blue spruces are commonly affected by cytospora canker especially those planted outside of their native range.
Colorado Blue Spruce
Symptoms of Damage
- Browning of entire limbs, starting low in the canopy moving upwards over time.
- Dieback of entire limbs that can be seen year round.
- White/blue sap oozing from infected branch lesions near the trunk.
- Very small fruiting bodies are extremely difficult to find near the margins of branch lesions.
- 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.
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. 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. Recent research conducted by Dr. Watson and Dr. Jacobs in the Journal of Arboriculture and Urban Forestry (2012) has shown that Cambistat™ can be used to promote tree health and has been shown to significantly reduce cytospora infections.
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. Cambistat™ treatments result in only moderate growth regulation of spruce (30-40%) which can also be desirable in areas where growth reduction is needed.
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 forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org