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Searcy, Ark. –
Hypoxylon Canker on Shade Trees
Hypoxylon canker is a common infectious disease of oaks in Arkansas that can affect
several species of shade trees. Oak is the most susceptible, but sycamore and elm
are affected also.
This disease is caused predominantly by the fungi Hypoxylon tinctor and Hypoxylon atropunctatum. These fungi are not considered aggressive “killers” but instead take advantage of
stressed or declining hardwood trees. Infected trees can be in various habitats, including
recent or well-established residential areas and forest trees. Canker diseases can
reduce tree growth, result in wind breakage, and weaken trees. These trees often become
more susceptible to attack by secondary wood rotting fungi and insects.
Most damage occurs on stressed or injured trees. Trees stressed by environmental extremes
and in danger of succumbing to Hypoxylon canker manifest symptoms typical of a declining
These symptoms include:
Cankers are usually localized dead areas in the bark of the stems or twigs and are
often recognized as a sunken, dead area. Sometimes, the healthy tissue immediately
adjacent to the canker may thicken and appear higher than the normal surface of the
tree. This callus formation around the diseased area helps limit disease expansion.
However, under humid weather conditions, cankers can rapidly enlarge to lengths greater
than 3 feet. The fungus usually kills the cambium and portions of the sapwood, creating
the affected trunk or branch areas, potential for breakage. If cankers girdle the
branch, the branch will die.
Stromata often become visible several months after the underlying tissues die and
are the most obvious signs of the disease. Splashing water and wind spread the spores
of the fungus to healthy trees.
There is no cure for this disease, but stress avoidance is the most effective management
strategy. The key ingredient to canker free trees is prevention. It is important
to avoid tree wounds. A construction injury, herbicide damage and site related stresses
(drought, etc.) contribute to disease onset.
Homeowners need to promote vigorous plant growth by correct fertilization and irrigation.
Fertilization should be based on a recent soil test. If practical, selective pruning
should be done to remove dead or damaged branches from the tree. This may help slow
the advance of the fungus. Tree removal may become necessary if structural integrity
becomes questionable, especially if the tree poses a threat to structures or people.
Homeowners should monitor canopy status and overall vigor. In urban areas, tree health
may need to be evaluated by a trained professional for the tree to be maintained properly.
For more information you can contact your local county extension service, you can also follow Sherri Sanders on Facebook @UADA.WhiteCountyAgriculture
By Sherri Sanders County Extension Agent - AgricultureU of A System Division of Agriculture
White County Extension Agent - AgricultureU of A Division of AgricultureCooperative Extension Service2400 Old Searcy Landing Road Searcy AR 72143 (501) 268-5394 email@example.com