ASH tree problem
No, we do not provide a list of companies that spray landscape trees. But we suggest you hire a Certified Arborist because s/he must pass an exam to be certified, and must acquire continuing education credits.
In the end, we suggest you interview at least 3 companies and, then, hire the one you are most comfortable with.
You can locate such companies in the Yellow Pages, either in a phone book or online. In the phone book, check the heading of Trees, Tree Care, or something similar.
Online, use a search phrase similar to this -- spray for tree disease.
Another option is to use your zip code to search for Certified Arborists at https://www.treesaregood.org/findanarborist/findanarborist .