Do Ladybugs Control Colorado Potato Beetles?

Last year, my first year growing potatoes, I had a big problem with Colorado Potato Beetles.

This may have been because the first time that I saw them, I was captivated. I mean, they’re beautiful insects. I noticed them, I admired them, I watched them a little, and then I went off, leaving them to their business.

Big mistake.

Because not too long afterwards, when I was out inspecting, there were not only adult beetles, but this.

These are potato beetle larvae, fattening up on my potato leaves. I can say this because it was at about this point last year that I bothered to find out what these bugs were and whether or not I wanted them there.

As it turns out, I didn’t.

They were also eating my eggplant. What to do about it? Well, pesticides were out, so the fact that they apparently become resistant to a pesticide very quickly was immaterial to me. I read a paper from the University of Kentucky, College of Agriculture that said:

“Potato plants can withstand considerable defoliation without yield loss. Plants can lose up to 30 percent of their foliage without yield loss. Generally, insecticides do not need to be applied unless there is more than an average of one beetle or larva per plant. Additionally, some beneficial insects such as birds, predatory stink bugs, and parasitic flies will help to reduce Colorado potato beetle numbers somewhat.”

This was reassuring to me, because from this I was able to ascertain last year that my problem with the potato beetles was not too bad. I had never seen more than one or two on a plant at a time, and when I walked through all my plants (I had about a dozen banana fingerling plants) I usually only found one or two plants that had any on them at all.

So, I added potato beetle patrol to my list of daily garden chores. Whenever I saw them I would pick them off and crush them. I managed to keep things relatively under control, and got pretty deft at pinching the larvae between the folds of the leaf they were eating. It was a messy and unpleasant business, but I did what I had to do.

This year I was thinking about potato beetles before the seed potatoes even went into the ground. As the plants got bigger (this year I have closer to 40) I kept a regular patrol, walking between the rows. I checked the undersides of leaves. I was vigilant, and my vigilance was rewarded with…

Well, as it turns out there was little to be vigilant about. I found and crushed a few adult beetles, then never saw another adult. I found one plant infested with larvae and over the course of a day or two managed to find and crush them all. There were stray larvae on a few other plants. But that was it. My potatoes remained largely uneaten this year. What gives? What’s different? My gut feeling was that it is this: The ladybug.

I have tons of ladybugs in my garden this year. I didn’t import them. I don’t remember it being this way last year. They’re just there. Crawling all over my potato plants, my tomatoes, my peppers. I see them poised on the tips of straw. They land on my arm. They’re everywhere.

Still, in my usual fashion, I didn’t jump right up and start researching the issue. I just wandered around the garden, looking at the ladybugs, and thinking, Huh. I wonder if that’s why I don’t really have any potato beetles.

Then, finally, I sat down to a Google page and asked the question. It turns out that ladybugs are sold as a natural predator for, among other things, Colorado Potato Beetles. They eat the eggs. So my hardworking ladybugs probably cleaned up most of the damage done by what adult beetles did visit me, before I ever even knew it was there.

Lucky me.

I’m going to put this experience in the “win some” column.

  • Published on Jun 25, 2010
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