To spray or not to spray?

Earlier this afternoon I was interviewed by the local television station news program on the occasion of today being Canada’s National Day of the Honey Bee.

As I noted in my previous post, our city is currently being inundated with forest tent caterpillars. They are everywhere, and it’s hard to take a walk in one of our city’s wonderful green spaces without literally bumping into them at every turn as they rappel out of the trees above. Yesterday evening I spent a bit of time in my yard and then spent most of the rest of the evening removing strands of caterpillar silk that had festooned me.

What does this have to do with Honey Bee Day? Well, as the planned news story is bound to point out, the temptation for caterpillar-plagued homeowners is going to be to spray the heck out of the little leaf-munching critters with whatever pesticide they can get their hands on. That urge, I would argue, is a mistake for a number of reasons:

• At this point in the tent caterpillar infestation, they have done almost as much damage as they can do. I have been observing that they are growing quite well (unfortunately for us!) and are going to be entering their pupal (cocoon) stage shortly. In other words, spraying now won’t do much to reduce any remaining damage that they may still do. The damage is mainly done.

• In any case, in the face of such a massive infestation, spraying a can of pesticide at a few of the caterpillars is analogous to facing up against the JTF2 with a BB gun. You may inflict some minor damage for a moment, but you’re going to be overrun anyhow.

• For smaller trees and shrubs (many of which these caterpillars only eat reluctantly at best anyhow), physical removal is as effective as spraying, and definitely much better for the environment.

• And, spraying WILL impact other arthropods that are beneficial, including enemies of the forest tent caterpillar… and pollinators such as honeybees and various native pollinators (bumblebees and others).

That final point, I believe, is going to be one of the messages of the news item later today. Specifically, don’t lose sight of the forest for the trees.

Or, in other words, don’t lose sight of…

• the honeybees
• the native pollinators
• the spiders that eat garden pests
• the parasitoid flies that dine on tent caterpillars
• the ladybugs that eat your aphids
• the seed-dispersing ants
• the dragonflies that eat mosquitoes
• that beautiful swallowtail butterfly that brightens your day
• …you fill in the blank…

…for the caterpillars.

I realize that even after reading this, some folks are still going to want to buy a can or two of pesticide and use it in their yards. If that is you, then:

• be sure to carefully follow the directions on the label because they are there for a reason.

• remember that these are powerful chemicals and that more is not necessarily better.

• do your best to limit your application to the area in which you deem that it’s needed.

• protect yourself, your kids, and your pets during and after spraying.

I’ll close with a personal story. The other day I was in a garden store buying a few bedding plants and some soil for our gardens and containers. Near the checkout there was a display of pesticide that is labeled for use against forest tent caterpillar. A customer and a store employee were talking about how best to use the stuff. Being a nosy entomologist I joined the conversation and made my case. Following more discussion between the three of us the customer finally said, “well, I know that this won’t really help with the problem in my yard, but I’m just so grossed out by them that I want to do something.”

I’m not sure if she ended up buying the product or not. But I suspect that a lot of spraying goes on for that very reason – i.e. a general dislike of insects – particularly in vast quantities – combined with a desire to do something… anything.

So, one last plea – please carefully consider your need use a pesticide in this situation. This plague will be over for the year soon enough. If we are lucky, natural enemies and disease will knock the population down this year and we won’t be seeing these creatures in any substantial quantities for quite a few years to come. In the meantime pesticides will not alleviate the problem, but they might end up hurting some friends that you may not even know that you have.

If you would like more information on pollinator conservation, please see this page hosted by the Xerces Society.

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(And a small side note: I’ve been seeing a few “friendly flies” around lately. So hopefully their population levels will pick up and they’ll help to wipe out this infestation. Fingers crossed! Keep in mind that these creatures are called “friendly” for a reason. Specifically, they like to land on various surfaces, including people. But they are harmless to everything except for forest tent caterpillar cocoons. If they are going to be a factor in knocking down the tent caterpillar infestation, there are going to be a lot of them around very soon. Here is a picture of one so that you know what to look for. Click on the photograph to enlarge. Notice the stripes on the thorax, the pattern on the abdomen, and the nice, big reddish/burgundy eyes.)