One is an outbreak of the ash borer, a clear-wing moth, which looks similar to a yellowjacket wasp. Ash borer larvae tunnel in the inner bark and wood, causing branch dieback and sometimes tree death. Only one generation a year is known and adults emerge from April to mid June. Symptoms include bleeding, wilt, branch 'flagging' and eventual dieback. The ash borer is considered a secondary pest because it typically attacks trees that are under environmental stress, particularly drought.
Healthy trees are more resistant.
If found, then prune out damaged branches and burn the wood. This will prevent moths from inserting eggs in neighboring branches or trees. The goal is to minimize damage to the two trees and prevent damage to the rest of the tree row. Be sure to deep water your trees once a month during the summer. The second problem affecting Raywood ash also exhibits symptoms of branch dieback and tree decline.