If a tree has more than 30% of the canopy dead or dying, no treatment is helpful or recommended. We suggest removal sooner rather than later as dead ash trees lose their structural stability quickly.
If you have 30% or less of the canopy involved, the size of the tree determines whether you can treat it yourself or whether to hire an arborist to treat it for you.
Here is our page on Emerald Ash Borer :http://extension.umd.edu/hgic/invasives/emerald-ash-borer
It includes many informative links, including this chart that helps you know if you need a professional: https://extension.entm.purdue.edu/EAB/PDF/NABB_DecisionGuide.pdf