We suggest you work with a certified arborist who can evaluate the trees and look for signs of injury and sources of stress that might be remedied. There are several species of Ambrosia Beetle in Maryland, and while a few attack trees that appear healthier than others, the rest attack weakened trees and they all find hosts by "smell," by detecting chemicals trees release when stressed. This could result from roots that have suffered from repeated episodes of drought, or more often, roots dying from periods of oversaturated soil that deprives them of enough oxygen. Oaks are a diverse group and some are more tolerant of root flooding while others are more tolerant of drought. If you don't know the species of oak you have, the arborist should be able to help you ID it and will take that into account when making a diagnosis.

Ambrosia Beetles introduce a fungus when they tunnel into a tree, and as the fungus grows on the wood in their tunnel, the beetles eat the fungus itself, not the wood. Although the tunneling can destroy some of the tree's vital tissues, the growth of the fungus also kills or clogs those tissues, depriving the growth above of moisture and/or nutrients. This damage cannot be reversed even if the pests could be eliminated at that point. Once established inside the wood, neither the insect nor the fungus can be treated with insecticides or fungicides. A blog post by Ohio State University does a nice job of illustrating Ambrosia Beetle damage (in this case comparing it to the damage of similar bark beetles) and why they're not the primary factor in tree decline: Bark Beetles and Ambrosia Beetles.

The only chemical intervention can be made by treating tree trunks with a pesticide (usually a pyrethroid) that kills insects landing on the bark so the beetles won't be able to begin new tunnels, and knowing which species of beetle is present informs the pesticide applicator when to make the treatments based on its life cycle. Identifying Ambrosia Beetles is challenging since they are tiny and need microscopic examination to tell them apart. If the arborist cannot do this themselves, they might be allied with a lab or entomologist who can, if they can collect samples of the adult beetles. Unfortunately, those pesticides also have the potential to expose beneficial or other harmless insects or animals landing on the treated area. This is one reason why the ideal approach is to lessen tree stress when possible so the beetles never target it in the first place.

Miri