A large cascara tree in our yard appears to be dying. It has leaves only on the outer ends of its branches. Many of the inner branches were bare and apparently dead, so we cut them off. We suspect that the moles in our yard are to blame–that their tunnels make it harder for the tree’s roots to access water and nutrients. Does that seem plausible? We have tried to get rid of the moles, without success. Our only other treatment has been to water the tree thoroughly every week this summer. Do you have any recommendations? Thanks!

Given your description of the tree condition you're right to suspect some below ground issue affecting the roots. You could also check for a couple of fungal infections that present on the leaves or twigs. If the twigs have any little circular to irregularly shaped cankers that may be a sign of infection that can be addressed through cultural or chemical measures. Similarly the leaves may show small gray to brown spots on the upper surface or potentially orange protrusions from the lower leaf surface. If your tree is showing these signs there are some steps you can take a tree owner.

For canker on the twigs you can remove the affected twigs or branches and dispose of them. Be careful not to take too much though as you don't want to over prune an already stressed tree.

For leaf spot or rust you can rake up and dispose of the leaf litter as the tree drops its leaves this year. This extra step removes a source of future infection.

Finally I recommend a site visit by one of our arborists to assess the tree and determine the true source of the problem.