Elm Leaf Beetle HOWTO

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I never read Rachel Carson's Silent Spring, but I understand it opens with a description of spraying Elm trees. The book gets its name from the "silent spring" that resulted.

I used to own a house with a stand of about 5 Elms, and learned how to care for them. There's not a lot of information on Elms, and that's why I wrote this.

There are two types of beatles that commonly attack Elms:

  1. Elm Leaf Beetles
  2. Elm Bark Beetles

Elm Leaf Beetles defoliate the trees. I saw this happen 3 times in one year, although it's usually twice a year. The defoliation is similar to the effect of tent caterpillars. There are photos of these insects on the web, but they're much more identifiable if you've seen a live one before. I didn't even recognize the bug in the web photos. The infestation is immediately apparent from the lace pattern of the leaves which have been eaten by the larvae.

It is not apparent whether the effect of this defoliation is especially stressful on the trees, although it certainly looks bad. This may actually be a defense mechanism the Elms have developed, in order to attract birds and predatory insects to the tree.

Elm Bark Beetles burrow into the tree's bark. This results the tree being exposed to Dutch Elm Disease, a fungus. I think American Elms are resistant to this. Dutch Elm Disease is far more stressful to the trees, if you consider the fact that it kills them.

Actually it's the larvae which do the damage in both instances; not the adult insect.

What Happens if You Spray

It is common to spray for Elm Leaf Beetles. This is typically done by commercial outfits using a high pressure hoses which spray upward into the canape.

The pesticides kill the beetle larvae but also kill beneficial insects (predator beetles, praying mantas, wasps) spiders and birds, usually from the toxins ingested by the beetle larvae.

The spraying reduces the defoliation. This is because the Leaf Beetles populate in a cycle, so the application appears effective. This causes several worse problems!

One problem is that without the beneficial insects, the Elm Bark Beetles, which are on a different cycle, are unchecked. If they (the host trees; not the insects) are European Elms, they'll get Dutch Elm disease. The trees will die.

None of this addresses the issue of "incidental" spraying. So don't bother eating those strawberries you have growing beneath the trees!

And (back to Rachel Carson), you won't be bothered with too many of those noisy songbirds.


  1. Do nothing - then you have ugly defoliated trees. This also stresses the trees.
  2. BT (bacillotoxin) - BT is a natural pesticide but:
  3. Soap Spraying!

How Soap Spraying Works

First, keep an eye on the trees. You can see the beetle larvae on the trunk and the beginning of defoliation. That obviously means the beginning of an infestation cycle. If you miss that, don't worry because you'll see the defoliated leaves soon after.

The rest is simple. Just mix soap and water and spray upward. It kind of helps if you spray upward toward the trees! (:

I used to have a high pressure ditch pump and used one of those garden hose attachment sprayers with a siphon bottle. It only reached the lower 1/3 of the canape, but that was sufficient.

Since you probably don't have a high pressure ditch pump or the irrigation ditch to go with it, the easiest way is to go out and buy a pressure washer. Then set the spray to maximum distance and have fun!

You're probably as cheap as I am; otherwise you'd be hiring a landscaping contractor to take care of your trees. Look up the word "cheap" in the dictionary and you'll see my photo...

So if you're as cheap as I am (or almost as cheap as I am), you can try this with a garden hose attachment siphon bottle and tap water at ordinary water pressure. I hadn't tried it this way but it should work. If it doesn't, you'll have a couple of months to buy the pressure washer. They're available at most Hardware R Us stores like Home Depot.

Unlike pesticide application, leave your car out there because when you're finished, you can wash your car with the leftover soap!

There are commercial products out there, including Safer SoapTM. I prefer "Cheaper Soap"! I mixed cheap laundry detergent with water. (Did I mention "cheap"?) This is better than dish soap because it doesn't suds as much.

The Tree Spraying Service

The service I used was well-aware of this procedure and resisted discontinuing their spraying. Normally they just called and got approval. When I said "no" one time, they adjusted my account and the next time came out without my permission, including additional spraying such as spraying for aphids on an Oak. I had to complain to the state environmental agency and the EPA to get them to stop. (They probably would have stopped anyway, but it was clear that they strongly objected to people discontinuing the use of commercial tree spraying services.)

(The tree spraying service was in Boise, where this sort of thing is considered good business practice.)

So that's pretty much when I figured out the soap trick.

On the positive side, by using the soap method, your neighbours won't be complaining about overspraying onto their organic garden, pets and children!


Can this be done commercially?
Yes. There is no reason a lawn and garden company can't load up their tanks with a bunch of soapy water. It's cheaper and more competitive.

How do you make money on this page?
For just $12,000.00, our crack soap spraying team (photo on top of page) will come out to your place with a Mooney converted to a cropduster. We'll spray soapy water on your tree.

I also own a bunch of shares in Proctor&Gamble, and sell them lab animals for them to torture. The more soap you buy, the more lab animals I can sell.

Why did you feel you had to fight the tree spraying service? It was probably just a mistake.
As a matter of explanation, I had the most prominent small stand of elms in a very visible neighbourhood. The problem was that if I was able to maintain the trees without spraying, others in the neighbourhood would follow suit. Then the city, which maintained 50% of the elms (in parks), would perhaps follow. The nature of business' actions made it obvious that this was more than a "routine business" procedure. Another reason I felt it necessary to be adversarial was I didn't want them to come back and "overspray" from a neighbour's yard.

Can't I just go out when nobody's looking and perform a rude act facing the tree trunk.
Sure, but check the wind conditions and be careful about the overspray. Don't flush -- it disturbs the bees.

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