During severe outbreaks, trees can be completely defoliated. The tree may produce a new set of leaves but may also store the energy to set buds for next year’s leaves. It is unlikely that the tree is dead. Even if all of the leaves are gone it is important to water the trees on your property to provide them with the energy to grow new leaves.
In July 2021, for example, trees which had been completely defoliated have already grown a complete set of new leaves.