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Question from Mark, Sandy, UT (received 6/1/20) -

I have what I think is a type of olive tree. It is  mature tree that appears to be dying. There are golf ball sized sappy bulbs all along the main trunks. Several of the main trunks no longer produce leaves or new growth and appear completely dead.

Can you tell me what caused this tree to die? If it is a disease, should I worry for the other trees around?

Answer from Gabrielle Harden, USU Forestry Extension Educator (sent 6/2/20) -

This appears to be a Phomopsis canker which is caused by the fungus Phomopsis arnoldiae. Both the tree and the disease are exotic to this region, and this tree species is actually invasive in the West. This disease is very difficult to manage. Branches with cankers can be pruned in winter or early spring. To ensure the disease does not spread to other trees, it is wise to burn the diseased portions removed, though I am not able to see any other Russian olives on the landscape. This looks like a rather serious infection, and I worry it may be too late to save this tree. It will become increasingly unsightly and eventually die. Unfortunately, removal may be your best bet.

This is a common issue out east, so a quick Google search for 'phomopsis canker Russian olive' will generate many articles from universities in that region.

I hope this helps.