I receive many questions about tree and shrub problems. The following are the most commonly asked this year.
Question. My newly purchased Dakota pinnacle birch is dying from the top down. The upper leaves are drying up. Can you tell me what is wrong with my tree?
Answer. I have had over a dozen complaints about pinnacle birches. Even though these trees have a stunning central trunk and a columnar appearance they are dying from the top down. On investigation, these trees have all been infested with bronze birch borer insects. This is a very surprising situation for most people. That insect usually attacks larger and older birch trees. The tree has an Asian origin and has been further developed in the United States. It appears this tree is very attractive to the bronze birch borer despite being proclaimed resistant to attack by these beetles. There is no 'cure' for this boring and aggressively feeding insect. I recommend that it not be purchased until a more resistant variety of this tree is developed.
Question: My apple tree (or crab apple tree or mountain ash tree) has had its twigs shrivelled up this summer and looks like it is dying. The tree was growing fine and appeared healthy from the day we planted it in the garden. Do you know what is going on with my tree?
Answer: These trees have been infected with fire-blight disease. This has been one of the worst years I have seen for fire-blight-infected apple trees. I wrote about this disease in my last column. Fire-blight related questions totally dominate the questions I am receiving lately. I have noticed cotoneaster, hawthorn and pear have also been damaged by this disease. All affected plants are in the pome fruits section of the rose family. It has been a number of years since the disease has been this bad in southern Manitoba. I still find many people pruning the above listed plants in the late spring and summer which is absolutely the wrong time to prune wood that can potentially be infected. I always ask whether or not the pruning tools have been disinfected after each cut made during the warm season. Few people do this. Invariably pruning is done without proper sterilization of pruning tools with bleach and water, methyl hydrate or denatured alcohol. If in doubt sterilize pruning tools after each cut. Better yet prune in the fall.
Question: My Japanese tree lilac, ivory silk variety, has not fully developed its twigs this year and the flowers are much sparser than they have been in the past. Do you know what's going on?
Answer: I have looked at dozens of sick Japanese tree lilacs this year, and I see different things going on with the trees. I have a fine specimen of this tree species as do two of my neighbours. We all water the trees during dry periods of summer and we all fertilize them in the fall. I suspect the deep freeze we had during this past winter had an adverse effect on the growth of many of these trees. The over-wintering buds were definitely damaged by deep cold, either preventing leaves and new green shoots from emerging, or if the buds did open the leaves and shoots were too weak from cold stress to develop naturally. If your tree lilacs have at least half of their twigs with green leaves, I would definitely recommend you have your trees fertilized this fall with a suitable nitrogen and phosphorus fertilizer. If you contact me (preferably by email) I will send you information how you can properly fertilize small trees.
Michael Allen M.Sc.F., RPF (ret.) is a consulting urban forester, tree diagnostician and certified arbourist. He owns Viburnum Tree Experts, a Manitoba company that provides objective assessments of the condition and the care required for trees and shrubs on home and business landscapes. He is available to visit homes and gardens. Michael can be reached at 204-831-6503
His web site is www.treeexperts.mb.ca
viburnumtrees@shaw.ca
