Summer 2020 Mother Nature’s Moment
by: Lesley Bruce Smith, ISA Certified Arborist

It seems very counter intuitive that browning and dead leaves could be caused by too much water, but I wish I knew how many times in the last several weeks I have had to say to clients…”This is a problem that has been caused, or made worse, by cool, very wet spring weather.”

It is so easy for us to forget what the weather was like just a few short weeks ago. This spring was the third year in a row of record breaking amounts of rain in the Chicago area. In caring for trees we have learned that July and August is the most difficult months for trees, or at least those are the months in Chicago where the trees show us what is stressing them out.

We have seen SO many trees with fungal and bacterial issues in the last several weeks. We have even identified a number of new disease issues that we have NEVER seen before. A good example is Marssonina Leaf Spot on Cottonwood trees. This disease is one we have never seen in our area before.

The more common diseases that have caused real heartache these last few years are Apple Scab on Crabs, Cedar Apple Rust on Hawthornes and Cedars, including Rust issues on Serviceberries, and unfortunately, our continuing battles with Fireblight. The first few are all fungal diseases and the last is a bacterial disease. Additional details on all these diseases can be found in our Arborsmith Abstracts® by the same names. Suffice it to say, however, that most of the fungal diseases are not immediately fatal. They can cause real alarm when your beautiful Crab, Serviceberry or Hawthorne are shedding a lot of leaves in July and have ugly black/brown spots on the leaves. The good news about the fungal diseases are that your tree will come back next spring and if nature can cut us a break and not dump quite so much rain in the Chicago area we should see an abatement of some of these ubiquitous fungal problems.

As professionals in the tree industry who are dedicated to using non-toxic thoughtful solutions, we are concerned about the fact that our treatments, which are often organic, have not been strong enough to combat the HUGE fungal inoculum in our environment at the moment. We are talking about trillions and trillions of fungal spores that are all spread by rain droplets. The beauty about tree wisdom is that the mild wet weather also provides the trees with an opportunity to create huge numbers of leaves which are their food producers and they can stand to loose a lot of those leaves when the going gets tough without them declining in health.

Talking about fungi and bacteria often gives us a bit of the heebie-jeebies but we would all be dead without them and so would our trees. Our goal is to look at the big picture when combatting all these tree diseases and work to achieve the best results with the least impact to our environment and in a way that is safe for humans, and animals as well as our plants.

Backyard Wisdom - When Does Too Much Water Cause Trees to Die From Drought?

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