Branches Dying in Elm Probably Not Dutch Elm Disease

Elm leaf beetle damage

Q. I have about 10 elm trees and my neighbor has 4 or 5. The branches seem like they just die. This pass year I lost 2 complete trees. I have been told there is a elm airborn disease. Can you please tell if that is true and what can I do about it?

A. There is no airborne disease of elms that you have to worry about. I think there is some confusion about Dutch Elm Disease and these trees. Siberian elms are not as susceptible to DED as some other elms which are not planted here anyway.

            Most of the elms here are Siberian elms, an inferior elm for landscape purposes. By the way, one of my favorite large trees is Chinese or Evergreen elm, a very nice tree that grows well in our climate with very few problems. 

            The usual disease problem we see on Siberian elm is a relatively harmless disease called slime flux. This is a bacterial disease which invades the wood and causes basically fermentation inside the trunk and large limbs. ooze from the bacteria is pushed out of the trunk or limbs and weeps down the side of the tree frequently from a pruning cut. If you get close to this ooze it will smell like fermentation or yeasty.

Wetwood or slime flux comig from
pruning cut

            This smell frequently attracts flies to the ooze. It is thought that the flies can pick up this bacterial contamination and spread it to new wounds on several trees besides Siberian elm. If we see this particular disease on the tree we usually ignore it since it really does not cause any long term ill effects.

            As far as insects go the worst problem is elm leaf beetle which skeletonizes the leaf. We usually ignore this too since it usually does not cause severe damage to the tree but does cause the leaves to become unsightly. These trees are tall/large with the leaves very high in the air so damage to them is usually ignored. It would be very costly to spray these trees to control this problem.

            The last problem we have had with Siberian elm is when older landscapes with these elms growing in lawns is converted to rock landscapes. Frequently there is not enough water applied for these trees to continue to be healthy and the branches die back due to lack of water and a poorly designed irrigation system for the elm to survive.