Are you sure you need to cut it down?

Avoid falling victim to black walnut tree removal scams.

Look out for unusual wilting or death of otherwise healthy black walnut trees. Photo dredit: Ned Tisserat, Colorado State University

Look out for unusual wilting or death of otherwise healthy black walnut trees. Photo dredit: Ned Tisserat, Colorado State University

It’s officially autumn, but fall foliage colors have only just begun showing. However, if you have black walnut (Juglans nigra) trees you may have noticed that they are noticeably dropping their leaves. This is normal behavior for this species. Due to the threat of a potential new fungal disease, Thousand Cankers Disease (TCD), some landowners are being scammed into getting these trees removed unnecessarily. 

Officials from the Michigan Department of Agriculture and Rural Development (MDARD) have reported in a recent consumer advisory that scam artists are attempting to convince landowners that TCD has been detected in Michigan, and that they should harvest and sell their black walnut trees to combat it. Thousand Cankers Disease has not been detected in Michigan at this time. The closest confirmed location of TCD to-date has been in the Yellowwood State Forest in southern Indiana

Michigan residents should be on the lookout for TCD, however. This disease is a legitimate threat to Michigan’s black walnut resource. It is known as a disease complex because an insect, the walnut twig beetle, sometimes carries the TCD fungus and introduces it to the trees when it bores into its branches to lay its eggs. The fungus then spreads within the beetles’ galleries, causing cankers to form just underneath the bark. Although an individual canker may not be very large, their accumulation will girdle a branch or stem, cutting off the flow of water and nutrients. Eventually, TCD will kill the entire tree in this way. 

How would a resident know if they have TCD? First, make sure that the tree is indeed a black walnut (Juglans nigra). The disease will not infect any other species in Michigan. Black walnut trees have compound leaves containing 11-23 slightly fuzzy leaflets that have a very pungent smell when crushed. Mature trees generally reach 70-80 feet, with deeply furrowed bark arranged in a diamond-shaped pattern. The most obvious characteristic is their rather large, hard seed (nut) surrounded by a green husk that turns brown-black as it ages. They are commonly found in backyards, fencerows and edges of woodlands in the southern portions of the state

Unfortunately, the walnut twig beetle is extremely tiny and difficult to detect, and are difficult to distinguish from other related bark beetles. The most obvious sign of early infection is unusual wilting and yellowing of leaves or dying branches that have no other evidence of wounding or breakage during the summer. Infected branches can have evidence of small brown cankers just underneath the bark. Determining the presence of TCD, however, requires expert diagnosis. If you suspect your black walnut may be infected, contact MDARD Customer Service Center at .(JavaScript must be enabled to view this email address) or (800) 292-3939. 

Want to become more involved in helping keep TCD and other threats out of Michigan’s forests? Michigan State University Extension has launched the “Eyes on the Forest” program to recruit volunteers to monitor selected sentinel trees for potential invasive forest pests and diseases. For more information, contact .(JavaScript must be enabled to view this email address), outreach coordinator or .(JavaScript must be enabled to view this email address), entomology professor, to participate in this critical program. Learn more via the Midwest Invasive Species Information Network (MISIN) or by visiting the website

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