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Black Walnut > Trunk/Branches > Sunken, cracked or discolored areas along branches or trunk

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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 Cracks

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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
1/32^nd 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