How to Beat or Control Mexican Bean Beetles

How to Beat or Maybe Just Manage Mexican Bean Beetles

I have been dealing with Mexican Bean Beetles since before I knew what they were called, with varying degrees of failure. Never completely successful, at least not yet. I’ve been battling them at least 15 years, but, it is important to note, not all 40 years of my adult gardening and bean raising life.

We moved ten years ago this month and while we certainly had bean beetles in our earlier garden, I know there were many years when we had zero or very few of these destructive and prolific pests. Early on, if I had had them to the degree we’ve had them the last few years, I think I would have given up raising green beans (like I’ve given up trying to raise broccoli, due to the worms they get). Why some people can garden for years without any bean bettles or few, is beyond me. According to my research online, these bean beetles are more and more ubiquitous.

But this year, I have had the first success in keeping them more at bay, and I hope it is worth reporting here and sharing for all you fellow bean beetle sufferers. Stay tuned.

The adults looks like this.

The maturing larvae look like this.

The baby eggs look like this.

I hate all of them, especially when there are a bunch of the larvae on one bean leaf that make me absolutely “grively.” As below:

If you don’t know what grively means, it is a family word which means seeing something, usually in a pattern and something yucky that makes me turn away, shut my eyes, grit my teeth and shudder. They are so so gross! (I could barely stand to post the above photos… but I’m doing it for ya’ll.)

While my husband and I are not organic gardeners, we only use pesticides when absolutely necessary. In the early days 20-25 years ago, I did use some bean powder; maybe that’s what controlled them at that stage. But in recent years, our control method is simply picking off bugs and letting them drown (happily!) in a mixture of bleach and water (2/3 bleach, 1/3 water).

I have tried homemade mixes which included dish soap, rubbing alcohol, and mouthwash. Don’t try this at home. I REPEAT, DO NOT USE THIS HOMEMADE mixture. It killed my bean plants, totally dried them out.

Generally, when the plants get riddled from the bean beetles chomping away at them to the point they are no longer producing, I pull up all the plants, stuff them in garbage bags, and stomp (repeatedly) the soil where they stood, in order to kill the remaining larvae. I understand that the adult beetles overwinter in dirt and wood. Mother Earth News describes their life cycle here, and Weekendgardener shows the various stages here.

SOoooo given all of this, and having already handpicked likely 10,000-20,000 (counting dozens of eggs on leaves which I just smoosh in one fell crush) in my life so far, I was happy to read about Wade bush beans, which were said to be somewhat resistant to Mexican Bean Beetles. I bought 4 ounces of seeds and they are expensive, but the things I noticed were:

1. The leaves are very sturdy and thicker—more leathery. (Less tender and tasty perhaps to the beetles?) than the leaves of my Jades or Tenderettes that I had previously grown as bush beans.
2. The eggs that were laid seemed to dry up on the leaves and not mature into larvae as much—many of the eggs look dead or inactive.
3. The adult bean beetles seem a little more sluggish and dull—not so lively and quick to escape my fingers.

These things could all have been my imagination, but whatever. I have had far fewer beetles so far, and the bean plants and leaves remain viable and producing beans, for about 3 weeks now. I have also not seen any pupa stage beetles. Yet.

The Wade beans at Adaptive seeds (based in Oregon, who said they originally secured them from Germany) were a little more pricey than at my local seed store, but worth it. So far, my family members who’ve eaten them have liked them just fine.

We’ll see what happens when my husband’s fav McCaslan pole beans start growing more and bearing (read the story behind these southern favorite beans). We always plant them later as a bean that can grow and thrive late into the fall. Let’s hope!

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If you garden, do you plant bush beans? What kind(s)?

Do you get these nasty bean beetles? What are your methods of pest control?

Do you have a family word like grively? Does anyone know if it comes from Pennsylvania Dutch, (which my family knows a little)? 

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If you garden and preserve foods, here’s my favorite canning/preserving guide: Saving the Seasons: How to can, freeze, or dry almost anything. Purchase here.