What is golden canker? Golden canker (officially known as Cryptodiaporthe canker) is a visually distinct and increasingly common disease of alternate-leafed dogwoods such as pagoda dogwood. This disease can potentially be lethal if infections occur on the main trunk of a tree.
What does golden canker look like? Initial symptoms of golden canker include wilting and death of leaves on infected branches, followed by branch dieback. Infected branch tissue turns a bright, golden-yellow color. Oftentimes orange spots will be visible scattered over this yellow tissue. These spots are fruiting bodies (reproductive structures) of the fungus that causes the disease. If unchecked, golden canker can spread from infected branches to the main trunk, resulting in the death of the tree above the point of trunk infection.
Where does golden canker come from? Golden canker is caused by the fungus Cryptodiaporthe corni, which survives in infected branches. The exact means by which this fungus is spread is not known.
How do I save a tree with golden canker? The only effective way of managing golden canker, once infections have occurred, is by removing diseased branches. Prune four to six inches below the golden-yellow tissue on each infected branch. To prevent accidental spread of the golden canker fungus from branch to branch, and from tree to tree, be sure to disinfest pruning tools between each cut by dipping them for at least 30 seconds in a 10% bleach solution or 70% alcohol (spray disinfectants that contain at least 70% alcohol can also be used). Dispose of infected branches by burning or burying them. Fungicide treatments are not currently available for this disease.
How do I avoid problems with golden canker in the future? Reduce tree stress as much as possible. When planting a new pagoda dogwood, place it in a cool, shaded site. Remove turf from around the base of the tree out to at least the drip line of the tree, and apply shredded hardwood, pine or cedar mulch in this area to help keep the tree’s root system cool and moist. On heavy clay soils, use three inches of mulch. On other soils, use three to four inches of mulch. Be sure to keep mulch two inches from the main trunk of the tree. Also, make sure the tree receives sufficient water (approximately one to two inches per week for newly transplanted trees; approximately one inch per week for established trees). If rainfall is insufficient, use a drip hose or soaker hose to apply supplemental water. Fertilize trees as needed, but be sure to base any fertilization on a soil nutrient test.
For more information on golden canker: Contact your county Extension agent.
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