I was talking to someone today, and it came up that they asked me how long I've been working with trees. I had to think about it for a minute and do the math before I realized it's been 29 years this month (hey, I started young). I've been curious about trees and everything that affects them, and trying to learn as long as I've been doing it; one thing I've learned is that no matter how long I do it, there's always plenty more to learn. Besides the fact that there are always new things that come up, there are all of the things that I learned in the past, years ago, that I've forgotten since. I'll see something and just know that I've seen it before, but I just can't remember what it is, even after wracking my brain. This happens every year with something; a plant I learned before, a leaf spot on a particular tree, whatever.
There are the pests and diseases that recur every year or at least so often that you come to know them so well; those are the things that make people think you're a professional when really, you've just seen something enough to know immediately what's going on. But I guess that is what a professional is, isn't it?
"Why do my dogwood leaves look like this?"
"That's powdery mildew"
"Wow, how do you know that?"
"After a while, you just do."
But it's those weird things that pop up and throw you off that really test your abilities, that are your opportunities to keep learning, or are the good opportunities to remind you don't know everything; not by a long shot. There are countless fungal pathogens, insects and mites; there are nematodes, viruses, bacteria and mycoplasmas that can cause problems; there's no way to know them all. Sometimes abiotic disorders will express themselves in really strange ways. Many of these things can pop up all of a sudden, seemingly without notice or reason, but there's always a reason. You may never learn what it is, but you can try.
I'm of the school of thought that in general, most tree species each have their own common strengths and their own common weaknesses. Black locust have wood that is incredibly strong and decay resistant except for Phellinus robiniae, which they commonly get after locust borers attack them, and they get leaf miners every year. White oaks are very hardy and pest-free in general but certain years they'll get leaf blisters, or occasionally if conditions are right, they'll get anthracnose. Tuliptrees around here will get aphids or scale, usually it's no big deal. There are all kinds of things that chew leaves and spot leaves, so many that there's no way to learn them all, especially because most of the time they're harmless and cosmetic issues that don't warrant a treatment. But sometimes, something new shows up that either is a problem, or at least appears to be a problem. This year in the mountains the biggest one by far is the yellow poplar weevil.
Early June, after a warm dry May, tuliptrees all over the mountains started showing brown leaves on the tips of branches and the very tops of crowns. Soon, looking miles across ridges you could see the rusty brown tips of tulip poplars stretching back as far as you could see. When it first showed up I had no idea what was going on, because I'd never seen it before. After a few leaves started falling you could look and see the spots where insect feeding had occurred, but I couldn't figure out just what was feeding on them, I didn't happen to see the insects because I was only seeing the fallen leaves. After a while I figured out what it was and that it was a rare outbreak that seemed to be extending up the southern Appalachians into West Virginia. Luckily, it's really not that big of a problem— but it sure is dramatic!
My point is...what is my point, anyway? I guess the point is that mother nature will always keep us on our toes; when you're a professional it's not just about knowing the obvious problems, but knowing how to figure out the weird ones. It may involve looking in some books, or internet searching, or asking colleagues, or sending in samples, but in making the effort to continue learning we better ourselves as professionals and those we serve by helping to make appropriate management decisions. Besides that, nature is endlessly fascinating!
-- Written by Michael Davie, Snow Creek Landscaping