How do we protect our elm trees from Dutch elm disease?
We have been treating three large elm trees to protect them from getting Dutch elm disease since the early 1980s. For many years, they were treated using Arbotect every three years. In 2009, the trees were treated with Propiconazole and treated again on June 1, 2013. Now an arborist has stated Propiconazole treatment is good for only one year. We are confused--please enlighten us.
There are many factors that determine how often a tree needs treatment, and I cannot find a definitive answer to your particular situation. However, I might call several certified arborists and see what they say. Here's a link to information on finding reputable certified arborists: How to Hire a Professional Arborist to Help Care for Your Landscape Trees.
Here is a link to information from the University of Minnesota regarding Dutch elm disease: Dutch Elm Disease
Should I be able to find additional information, I will pass that on to you.