bark beete can kill trees totaly, but it often attaks hill trees weakened by disease, drought, smog, conspecific beetles or physical damage.
Confidor is an insecticidal compounds not selective that doesen't go into the wood and than it kills only the adults out of the tree and not the ones inside. And not only bark beeltle.
I stay to look at the situation, maybe trees can limit the invasion to the branches more run-down and continue to grow.
Look at the other trees near them so to understand if the invasion is limited to Cypress or hits also other kind of trees.
I hope to succed in relplying you correctly.