Thyronectria Canker

Thyronectria Canker (Honey Locust)

Typically, the best way to ensure the longevity of a tree is to simply keep it healthy. Soil aerating, watering, and feeding are necessary for your tree to flourish and to exert all the benefits you expect. With regard to Thyronectria Canker on Honey Locust, drought stress is often the initial instigator of disease. This fungal infection enters the tree through wounds, as do many diseases.

Unfortunately, there is no quick cure, and there is no magic spray to eradicate this fungus. The only opportunity is to identify and manage the stressors that are impacting the tree. Sustaining vigorous tree health is still the best defense against this disease. Since drought stress complicates the matter, many tree owners do not understand that trees require ongoing care, watering, and attention in order to maintain health and vigor.

The disease is characterized by sunken, discolored patches of bark, and can affect both new and old growth on branches and trunks. As the infection progresses, affected branches begin to die back from the tip, leaving the tree appearing weak and on the decline. The fungus spreads on older wood by entering through lenticels (tiny holes in the bark) or through wounds caused by lawn mowers or additional landscaping practices.

The cankers are typically elongated, sunken areas of bark with a callus ridge around the edge. Eventually, these areas turn from orange-brown to yellow-orange. The symptoms of the disease include the presence of annual and perennial cankers of various sizes on trunks and branches. The cankers can girdle the tree or branches, resulting in the dying off or yellowing of foliage, and subsequent dieback of twigs and branches. After the bark dies, the fungal mycelium will push out of the canker to produce spores to further advance the disease.

To aid a tree’s resistance to this pathogen, increase its vigor through proper watering during hot, dry times and a balanced fertilization program. While pruning and discarding infected wood and branches can help the tree aesthetically, it does not help cure it. Regrettably, many Honey Locusts will eventually die from it.

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