Xtremehorticulture

Xtremehorticulture of the Desert

Branch Dieback in Olive Sign of Soil Disease

Leave a Comment / branch death, branch dieback, olive, olive death, olive dying, verticillium wilt /

Q. We have a twenty year old olive tree in our front yard diagnosed with Verticillium wilt disease. The north third of the tree appears to be healthy. If we remove this tree, what distance from the old hole is needed for the new tree? We would a replacement tree to provide shade. We are looking at oak, pine, ash, spruce or fir.   Olive leaf drop and branch dieback may be a sign of verticillium wilt in olive. A. That’s unfortunate. Hopefully the diagnosis was correct and it is not something else that caused it. The information you received about the disease sounds correct. This disease is present in the soil and enters the tree via the roots.             Olive has very few pest problems and an excellent tree for the desert. Verticillium wilt disease is rare in olive here but does occur. Symptoms include the death and dieback of individual limbs for no apparent reason.             Trees resistant to Verticillium wilt disease and good choices for you in our desert include live oak such as Heritage or holly oak, ornamental pear, European pear, honeylocust, apple, crabapple and any of the conifers such as pines.             Eucalyptus is also resistant but a lot people do not like eucalyptus since it can be “messy”. I would not recommend spruce or firs since they do not grow well in our climate.             If you want warmth from the winter sun then conifers (pine) or any evergreen tree (such as our southern oaks) is not a good choice for you. I would stay with ornamental pear or honeylocust for seasonal shade, disease resistance and good looks.             If you stay with Verticillium resistant trees, planting in the same general area should not present a problem.

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Branches Dying in Elm Probably Not Dutch Elm Disease

2 Comments / branch dieback, desert landscaping, lm leaf beetle, sap oozing, Siberian elm, slime flux, wetwood /

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.

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