Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Black Walnut > Tiny to small holes in trunk or branches
Black Walnut > Trunk/Branches > Tiny to small holes in trunk or branches
1 of 3
Yellow bellied sapsucker
Sphyrapicus varius
- Evenly spaced holes in main stem, approximately ¼ inch, arranged in a linear or columnar pattern
- More information on Yellow bellied sapsucker
2 of 3
Flat headed apple tree borer
Chrysobothris femorata
- ¼ inch oval-shaped exit holes present
- Older tunnels cause cracks in bark, froth oozes from openings
- Infected areas of tree show sunken, darkened areas of bark
- Larvae tunnel under bark of large branches and trunk
- Can cause dieback or entire tree can be killed, especially young trees
- Larvae is yellow with no legs
- Adult is ¼ to ½ inch long, flattened beetle, ranging from metallic brown to dull gray
- More information on Flat-headed apple tree borer
3 of 3
Thousand canker disease
Geosmithia morbida
- 1/32nd inch or smaller exit holes from the walnut twig beetle may be visible on dead and dying branches
- 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
- 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
