Dutch elm disease
We have a large elm tree that has started getting Dutch elm disease. We have had it injected every year. Last summer it was given an injection of Arbotect 20-s. Since it is on our easement the city of Ann Arbor has been trimmed it back on one branch to where there is no disease present. They suggest having it injected again. What would be the best chemical to use for this.
Washtenaw County Michigan trees and shrubs
There are a few fungicides on the market labeled for Dutch elm disease. They are considered to be more effective when used as a preventative which is done when leaves are approaching full size in late May to June. Some are labeled as therapeutic but often claim that the disease should have infected no more than 5% of the canopy. These treatments are done late June through August. Thiabendazole and Propiconazole are often utilized in managing DED. See the following article for more details. https://ohioline.osu.edu/factsheet/plpath-tree-04