Canker diseases are caused by fungi or bacteria that enter open wounds on many tree and shrub species caused either by insects or mechanical damage. Cankers can vary in size and shape and often appear on stems, branches or trunks, structurally weakening entire plants.
Canker Disease Symptoms
Cankers appear often localized as brown-to-reddish lesions on the bark of trunks and branches or as injured areas on smaller twigs. Sometimes sap or moisture oozes from splits between the diseased and healthy tissue, giving off a foul odor. The first symptoms of affected branches are usually visible on leaves which may look smaller than normal, curled and pale. When a fungal pathogen invades bark and sapwood, the vascular system tissues become blocked or die, causing wilting and dieback.
Canker Disease Causes
A variety of environmental conditions, such as prolonged cold weather or drought, flooding, hail, high winds, nutritional imbalances and transplant shock lead commonly to stress in shrubs and trees. In addition, mechanical injuries from lawn mowers and vehicles, animal damage, pruning wounds, root rot, insect borers and improper planting can lead to infectious fungi or bacteria entering wounds leading to canker diseases.
Problems in Fruit Trees
Bleeding sap on stone fruit trees such as apricot, cherry, peach, and plum can be caused by fungi of cystospora canker and may become problematic in orchards. When plants have been damaged mechanically or by boring insects, sawdust or pieces of bark are often observed mixed in the sap. For diagnosis, it is important to differentiate between insect infestation, mechanical injury, and infectious disease.
Canker Preventative Measures
Keeping plants healthy by not injuring them mechanically in the first place is key to minimize the chance of canker diseases. Choosing and planting varieties that are resistant and adapted to the area and site make a big difference. Proper planting, mulching, watering, soil management, pruning and winter protection practices encourage vigorous and healthy plant development.
If a canker infection occurs on twigs or branches, affected parts should be removed several inches behind the infection. Pruning cuts should be made at the branch collar and avoid leaving stubs. Between cuts, pruning tools should be sterilized using rubbing alcohol or bleach. Any type of trunk canker removal is best left to a professional certified arborist.
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