English walnut tree

English walnut tree in the Meadow View subdivision west of Cedaredge exhibiting severe branch dieback and excessive suckering due to a yet to be determined environmental problem of disease.

By Jim Leser

How many of you have wished to have a landscape problem addressed by a visit from experts? The Colorado Master Gardeners offer this for a fee of $25. But once a year the Cedaredge Tree Board devotes a day of free yard visits for the first 15 lucky people from the Surface Creek area to sign up. We finished this year’s visits a week and a half ago, and I thought you might be interested in some of what we found.

The No. 1 puzzling problem we encountered was significant branch death in many walnut trees. I had already observed this problem during two earlier house calls and a drive-by look at a tree I had trapped for walnut husk flies in previous years. During our Saturday visits we saw four more trees with similar symptoms, major branch dieback, often associated with significant suckering at the tree base and along many of its still living branches.

In further consultation with experts with Colorado State University in Grand Junction I found that other area Western Colorado walnut trees had suffered a similar fate. Their best theory is that the very rare combination of an early fall freeze in 2019 coupled with a dry winter and spring, followed by a late freeze in the spring of 2020 caused this branch dieback in walnut trees. The earlier concern for the deadly thousand canker disease appears unwarranted. Unfortunately there is not much that can be done except prune out the dead branches and eventually the suckers as well. The suckering is a response by damaged trees to balance its top growth to its existing, undamaged root system. Only you can decide whether your damaged tree is worth saving. At best it could be a severely deformed tree, taking several years to recover.

We saw several instances of drought stress, most commonly in aspens and spruces. We often find that these and other trees are being watered near their base. This is not where the feeder roots are. Move your watering out at least to the canopy edge, if not even further out. Drought symptoms can also be manifested when trees are watered too frequently resulting in roots exposed to continuously wet conditions. We advocate applying more water but less frequently, allowing the soil around the roots to dry out some. I usually water my trees once every three to four weeks, soaking the entire root zone for one hour.

Some trees will grow extremely long branches. These are prone to breakage, acting like sails in the wind. This can be hazardous for people and buildings. Elms are notorious for having extra-long branches and “lion tail” pruning will promote this problem. The correct way to deal with this is through reduction pruning. We don’t just whack off the end of a branch. What we recommend is to reduce branch length by cutting back to where a natural branch fork occurs.

Another problem we encounter quite often (this year was no exception) is improperly prepared balled and burlapped trees prior to planting. Once a tree is placed in its final position in the planting hole, we advocate removing the plastic wrap, cutting the twine used to tie the wire cage to the trunk, cutting down the wire cage at least halfway down and cutting the burlap off at least halfway down the root ball. This advice can help avoid circling roots. But don’t do anything to disturb or break the root ball.

Lastly, we saw the usual assortment of dying stone fruit trees (apricots, peaches, cherries, tangerines). These trees are very susceptible to the disease, cytospora canker, which will eventually kill a tree, but not right away. I would not remove any infected fruit tree until it no longer is producing fruit. While this infection can spread to adjacent healthy fruit trees, cytospora spores are ubiquitous and cannot be avoided by just removing infected trees. Your best bet is maintain healthy trees and avoid wounding susceptible trees.

That’s it for now. Enjoy your summer flowering plants which are just now coming into their glory. Blooms of hummingbird mint (hyssop), Russian sage, catmint, yarrow, hummingbird trumpet (Zauschneria), blanket flowers, and cone flowers are sure making my yard come to life.

Jim Leser retired to Cedaredge in 2007 after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a Colorado Master Gardener.

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