Leaves on Plum Tree Turned Yellow and Fell Off

I bought two Italian plum trees about four years ago.  They are 50 feet apart.  Several weeks ago all the leaves on one of the trees started turning yellow and have now fallen off.  What can I do to save it?

Several pests can cause leaves to wilt and yellow.  Before treating for a pest make sure it is not an environmental factor causing the problem.  Check the soil moisture and make sure the tree is receiving adequate water.  Too much or not enough water can cause wilting and leaves to drop.  Even established trees suffer during extremely hot and droughty summers.  Gardeners often overcompensate with improper watering.  Both can cause the symptoms you described.  The affected tree may be in an area that stays wet longer or dries faster than the healthy plum tree.  Adjust your watering schedule accordingly.   If this is not the problem, the tree may be suffering from bacterial canker, verticillium wilt, or various viruses.  These diseases can cause the damage you describe.  There is no control once the whole tree is infected.  Purchase disease-free plants and do not plant plums and other susceptible plants in the same location.  Borers feeding in the trunk can also cause the leaves to wilt and dry.  Look for holes in the trunk of the tree.  Treatment is difficult since this insect feeds under the protection of the tree bark.   Make sure the trees receive sufficient water and keep the soil cool and moist with mulch.  Properly tended trees are better able to fight off insect infestations. Badly infected trees will need to be replaced.

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