Keeping the Diagnosis Simple

Issue: 
July-August 2003

IT HAS ALWAYS BEEN MY HOPE to discover some new insect or disease affecting trees. However, experience has shown that the tree problems I see are usually simple and common. Let me give you an example of how I learned this fact the hard way.

In the summer of 1987, I was working for the City of Toronto’s Forestry Section as an Integrated Pest Management Inspector, a newly formed student position. I had just graduated from school and spent my spare time at work reading about all of the potential problems that could affect trees.

Pedro Nortes, a Tree Inspector, came to me with a problem in July. A large silver maple on the boulevard was dropping globs of reddish, juicy material which splattered a homeowner, prompting the complaint. What could be causing it?

I knew just enough to know that silver maples produce keys, not berries. I remembered recently reading about mistletoe, a parasitic plant that attaches itself to branches in the upper canopy of trees. It produces berries, which could explain the bombs of juice and seeds falling to the ground. This had to be the answer.

An aerial crown examination was in order to search for the mistletoe. A bucket truck was called off the regular pruning route to take me for a ride to the top of the tree. As the bucket lifted me up, I watched a number of squirrels running around the tree.

With increasing dismay, I remembered that white mulberry trees were full of luscious, ripe, red fruit, just the colour of the dropped "bombs." The aerial crown inspection failed to show any signs of mistletoe and I was forced to admit that we were investigating a classic case of squirrel poo.

I keep this embarrassing incident in mind when I’m inclined to think about exotic insects, diseases and parasitic plants that are not "normal" for Ontario. The answer usually lies with the boring, tried-and-true problems that we see every day – root injury, drought, poor soil conditions, common insects and disease. KISS – Keep It Simple Stupid.

I still harbour the hope that some tree problem may be named after me as the honour for discovering it. I just had to learn the hard way that my dream may never come true.

— Patricia Thomson, B.Sc.F. Consulting Arborist, Kelly’s Tree Care Ltd.

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