Cankers, diebacks, and wilts

Cankers, diebacks and wilts are caused by pathogens that infect stems, branches and roots. Because these pathogens affect the water conducting tissues they are considered serious, and in many cases, life threatening. A canker is caused by either a fungal or a bacterial infection. It may appear as a localized lesion or as a discolored/distorted larger area associated with a stem, branch or trunk. Cankers often have discolored areas that become dried out and shriveled so that the outer tissue or bark is wrinkled. In other cases, cankers can appear similar to normal tissue, but show up as flat spots on woody branches or trunks. Cankers commonly enlarge to girdle stems, branches or trunks, killing the water-conducting tissues and causing the death of upper branches or terminal growth (top). This form of dieback can also be caused by root rot fungal pathogens that have invaded the roots or the crown of the plant at the soil line.

Diebacks and declines are often associated with large trees that have been under stress due to adverse environmental conditions such as drought, excess water, and temperature extremes. These stress factors, often combined with poor planting sites, are leading cause of tree mortality. Once dieback and decline are present corrective action may be difficult. Control is best focused on prevention and site improvement. Do not replant the same species into a location where a plant has died of a root problem without making significant site modifications. Ideally plant a different species that is better adapted to the site conditions.

Wilt diseases can be caused by either bacterial or fungal pathogens and result in the interruption of water and nutrient movement to the leaves. These are of the most serious plant disorders and may lead to death within weeks to months. Because pathogens become embedded in the host tissue, they are essentially protected from external control measures. Often there is very little that can be done to manage these problems except to lessen any water stress by improving drainage, or in the case of drought, applying water. Fungal wilt diseases are common in both woody and herbaceous plants. Bacterial wilts are more common for herbaceous plants.

 

Other images

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Crown canker (Phytophthora cactorum) on dogwood (Cornus). photo from Oregon State University
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Smooth patch is a fungal disease that produces white-looking fruiting bodies on the bark of oaks (Quercus) at certain times of the year. Since the infected bark sloughs off naturally, no control is needed.
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Smooth patch disease on this white oak (Quercus) requires no treatment because it only affects the bark.
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Stem canker on rose (Rosa); note, darkened discolored patch
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Stem canker on rose (Rosa) caused by Leptosphaeria. Note distinct line of discoloration on the cane. FL DPI Archive, FDACS, Bugwood.org
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Stem canker on rose (Rosa)caused by Phomopsisa. Note wartlike bumps on canker. FL DPI Archive, FDACS, Bugwood.org
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Brand canker (Coniothyrium sp.) on rose cane (Rosa) in Spring, 2012. Note chocolate brown spots on stems.
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Brand canker (Coniothyrium sp.) on rose cane (Rosa) in Spring, 2012. Note chocolate brown spots on stems.
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This fragrant snowbell (Styrax obassia) died; the trunk and branches all had cankers on them, which may have begun as frost cracks
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A stem canker killed this fragrant snowbell (Styrax obassia), but it may have begun as a frost crack
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Close-up of scorched leaf of fragrant snowbell (Styrax obassia) that died of stem cankers
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Wilting and dying vinca (Catharanthus roseus)
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Discoloration of stems on wilting and dying vinca (Catharanthus roseus)
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Cut away showing vascular streaking in the stem of a wilting and dying vinca (Catharanthus roseus)
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Possible leucostoma canker on apple (Malus)
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Possible leucostoma canker on apple (Malus)
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Possible leucostoma canker on apple (Malus)
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Fruiting bodies of a canker on cherry (Prunus)
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Black stroma of Eastern filbert blight (Anisogramma anomala) on Harry Lauder's walking stick (Corylus avellana 'Contorta')
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Black stroma of Eastern filbert blight (Anisogramma anomala) on Harry Lauder's walking stick (Corylus avellana 'Contorta')
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Fruiting bodies (mushrooms) of a canker fungus on magnolia (Magnolia x loebneri 'Merrill')
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Fruiting bodies (mushrooms) of a canker fungus on magnolia (Magnolia x loebneri 'Merrill')
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Fruiting bodies (mushrooms) of a canker fungus on magnolia (Magnolia x loebneri 'Merrill')
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Fruiting bodies (mushrooms) of a canker fungus on magnolia (Magnolia x loebneri 'Merrill')
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Wilting and sudden death of a giant dogwood (Cornus controversa), cause unknown
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Curled leaves of a giant dogwood (Cornus controversa) that wilted and died suddenly, cause unknown
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