Black Walnut > Trunk/Branches > Sunken, cracked or discolored areas along branches or trunk
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Perennial nectria canker
- Early canker symptoms are small and difficult to see, usually forming a darkened, depressed area beneath smooth, young bark
- Sunken round to oval cankers with target shaped ridges of barkless wood on large branches or main trunk
- Red to reddish orange raised cushion like bumps can occasionally be seen on the edge of the canker
- Dead branches and twigs killed by girdling cankers
- More information on Perennial nectria canker...
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- Cankers are elongated strips of cracked sunken bark on lower trunk of young trees
- Wood is stained dark brown to black under bark in cankers
- Occasionally cankers will form higher on the trunk or on branches
- Wilting, canopy dieback and basal sprouting may accompany cankers
- Common on trees with cracks from cold damage
- More information on Fusarium cankers...
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- Vertical splits or sunken dead areas of trunk or branches that are primarily on the south and southwest side
- Occurs during winter, often noticed early spring
- More information on Frost canker...
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Thousand canker disease
- Leaves on one to several branches in the canopy turn yellow, wilt and turn brown
- Dead branches appear in the top of the tree, the tree eventually dies from the top down
- Groups of young green shoots often form on the lower trunk or branches of infected trees
- When the bark is peeled back, numerous gray to black oval cankers can be seen, often with borer galleries
- Bark surface may show no symptoms or may exhibit an amber stain or cracking immediately above cankers
- 1/32nd inch or smaller exit holes from the walnut twig beetle may be visible on dead and dying branches
- Currently not found in MN. If suspected, report it to the Minnesota Department of Agriculture at the "Arrest the Pest" Hotline: 651-201-6684 (metro) or 1-800-545-6684 (Greater Minnesota)
- More information on Thousand Cankers Disease...