Their job is to identify your trees and apply the EAB treatment if necessary. If you get start with an insecticides in the spring, you will have the best chance of saving the ash trees on your property.
If your tree is already showing signs of EAB damage, treatments may not be effective. It is unlikely that systemic insecticides applied as trunk injections, soil drenches, or soil injections will move very well in trees with extensive tunneling injury. Trees with more than 20% canopy die-back usually have extensive damage that will be difficult to overcome, even if the trees are protected from further attack by trunk and foliage sprays.