PDC, University of Missouri - Twig Blights and Cankers


	PDC Fact Sheet *Twig Blights and Cankers*

Cause: Twig blights and cankers are general terms for a condition where the sapwood of a twig or a shoot (twig blight) or a larger limb, branch or trunk (canker) has been killed. Twig blights and cankers are caused by a variety of fungal organisms and a few bacterial ones in either a secondary or primary manner.
Most organisms that cause twig blights and cankers are opportunistic pathogens. They are secondary; invading and infecting tissue only after it has first been stressed or injured by other organisms or conditions. Twig blights and cankers are commonly observed after late spring freezes, on recent transplants, on declining trees and shrubs, and on plants placed on unsuitable sites. Cankers at the base of trunks of trees and shrubs are common after injury by string trimmers.
Pathogens that cause twig blights and cankers in a primary manner are able to invade healthy, uninjured tissue. Diseases such as fireblight, Sphaeropsis tip blight and sycamore anthracnose are examples of twig blight and canker inducing diseases caused by primary pathogens.

Primary Hosts In Missouri: No host is immune to twig blights and cankers caused by opportunistic pathogens that invade stressed or damaged tissue. Certain hosts are susceptible to primary pathogens that cause twig blights and cankers.

Symptoms / Diagnosis: Sunken, discolored or different textured tissue from surrounding areas may indicate a canker (figure 1). Sometimes cankered areas have abundant resin or sap flow. Often if this area is viewed closely, fungal structures may be observed. The exact fungal identity often depends upon microscopic observation.

Integrated Management Strategies: There are no chemical controls for twig blights and cankers caused by opportunistic pathogens. These are managed by keeping the plant in vigorous condition. Affected areas should be pruning out whenever possible. Diseases such as fireblight, Sphaeropsis tip blight and sycamore anthracnose, which are caused by primary pathogens, sometimes may be managed by using appropriate cultural and/or chemical methods. The presence of twig blights does not necessarily indicate a serious problem. Some hosts such as river birch and willow are prone to twig blights even when vigorous. If a host is growing well and not unduly disfigured these should not be cause for concern.

Photo of tree trunk showing symptoms of a canker. Figure 1. A canker caused by Cytospora sp. on a small tree limb. The black spots with in the canker are the fruiting structures of the fungus.

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Email: plantclinic@missouri.edu

Cause:	Twig blights and cankers are general terms for a condition where the sapwood of a twig or a shoot (twig blight) or a larger limb, branch or trunk (canker) has been killed. Twig blights and cankers are caused by a variety of fungal organisms and a few bacterial ones in either a secondary or primary manner. Most organisms that cause twig blights and cankers are opportunistic pathogens. They are secondary; invading and infecting tissue only after it has first been stressed or injured by other organisms or conditions. Twig blights and cankers are commonly observed after late spring freezes, on recent transplants, on declining trees and shrubs, and on plants placed on unsuitable sites. Cankers at the base of trunks of trees and shrubs are common after injury by string trimmers. Pathogens that cause twig blights and cankers in a primary manner are able to invade healthy, uninjured tissue. Diseases such as fireblight, Sphaeropsis tip blight and sycamore anthracnose are examples of twig blight and canker inducing diseases caused by primary pathogens.
Primary Hosts In Missouri:	No host is immune to twig blights and cankers caused by opportunistic pathogens that invade stressed or damaged tissue. Certain hosts are susceptible to primary pathogens that cause twig blights and cankers.
Symptoms / Diagnosis:	Sunken, discolored or different textured tissue from surrounding areas may indicate a canker (figure 1). Sometimes cankered areas have abundant resin or sap flow. Often if this area is viewed closely, fungal structures may be observed. The exact fungal identity often depends upon microscopic observation.
Integrated Management Strategies:	There are no chemical controls for twig blights and cankers caused by opportunistic pathogens. These are managed by keeping the plant in vigorous condition. Affected areas should be pruning out whenever possible. Diseases such as fireblight, Sphaeropsis tip blight and sycamore anthracnose, which are caused by primary pathogens, sometimes may be managed by using appropriate cultural and/or chemical methods. The presence of twig blights does not necessarily indicate a serious problem. Some hosts such as river birch and willow are prone to twig blights even when vigorous. If a host is growing well and not unduly disfigured these should not be cause for concern.

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	Email: plantclinic@missouri.edu