You better watch your step if you are going to be selling ash treatments. There is no cure for the borer. AFAIK, there is only one chemical (Merit) that has shown any hope on preventative treatments, and it's not 100%.
The thing is, you can treat someones ash and the nieghbor next door won't. If the nieghbor gets EAB, the people you treated for will have their tree cut down, regardless of treatment.
EAB "treatments" are not something *I* would be looking to get into any time soon, especially with a new client base. I've been following the EAB since shortly after the anouncement it was here (by here I mean in-country), and it scares the crap out of me. I wouldn't want the percieved liability from treatment customers when their trees get cut down.
Just my $.02.