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What's bugging you? Oct. 24, 2018

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Nothing like a few days of rain to help us forget how dry and hot our summer was this year. My rain gauge has collected over 2.5 inches in the first ten days of October. And total rainfall this year is now equal to last year. But, and this is a big but, our drought conditions this year have been tough on our trees and it is apparent that many trees are struggling.

Because of our earlier dry conditions and progressive water rates in some communities designed to discourage excessive water use, many trees have suffered with branch dieback. This is especially true of maples, ash and aspen trees.

I've been queried by some folks as to why the dieback in situations where they followed their normal watering practices. Well it may be as simple as your watering regimen was marginal and with the increased drought pressure, that was enough to put your trees over the edge. In more average precipitation years you got away with your regular watering schedule.

There are some watering practices that are just plain harmful to trees. With newly planted trees, we apply water near the tree trunk to keep the root ball moist. We do this by either running a hose near the trunk, watering in a basin we have created around the trunk or by placing irrigation emitters close to the tree trunk. That is all well and good the first year but in following years you need to be watering out away from the tree trunk where the feeder roots are growing.

Another bad tree irrigation practice is to water frequently for short periods of time. This encourages roots to stay close to the soil surface where the soil dies out rapidly. Instead, water less frequently for longer periods of time. I water my trees about once a month for one hour, covering the area under the tree canopy as well as out a little ways from the drip line.

While on the subject of irrigation I must also warn about too much water, keeping the root zone saturated all of the time. This suffocates the roots and they die of oxygen deprivation. So deep watering less frequently should solve both of the above problems.

Now let's focus on aspens. First, planting aspens in areas below 8,000 feet elevation is asking for trouble. Especially in the more southern areas of their range such as where we live. Oh, you can find examples of older, flourishing aspens at lower elevations but they are exceptions rather than the rule. Also, aspens are generally short lived trees. An old low elevation aspen tree would be about 20 years of age.

And aspens grown where they struggle are constantly under stress, opening them up to all kinds of maladies such as diseases, insect infestations, off target herbicide injury, de-icing chemical injury, soil compaction, improper pruning practices and even improper planting. This year has been especially tough on aspens as evidenced by branches dying on what were thought to be healthy, thriving trees. Not so this year. What you are seeing is the effects of insufficient water.

What can you do to save these trees? Wait until spring to prune out those dead branches making proper pruning cuts. Rake up and dispose of all fallen aspen leaves. They provide an overwintering site for diseases such as marssonina blight. And consider spraying a fungicide on the developing leaf buds next spring. You may need to apply a second and even a third spray 7-10 days apart. And also spray the ground under the trees to suppress the overwintering blight that infects leaves when water splashes up into the tree. You should also water all your trees a couple of times this winter and every winter.

I know I've put a lot on your plate this time but trees are a long term investment and some of you have not been serious enough to properly care for your trees. Until next time, stay dry and pray for more rain and snow.

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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