I used to ask myself, “What’s a Mexican Bean Beetle?”
Now, every summer, I ask myself, “Of all the bugs in all the world, why does the Mexican Bean Beetle have to find my garden?”
The Mexican Bean Beetle is the worst of the worst when it comes to green beans. One day there is nothing there. The next day there are one or two Mexican Bean Beetles. Once you see the beetles, it’s almost too late to save your crop.
Mexican Bean Beetles are members of the lady beetle family. But they aren’t the Lady Beetle relatives you want in your garden. Copper-colored, about 6 mm
(1/4 inch) long and 5 mm (1/5 inch) wide, with 8 small black spots on each wing, the adults resemble large lady beetles but they’re really wholesale destruction machines. And they come in force.
How do they find your garden and your bean plants so quickly?
Chances are they never left when the winter came; they simply tucked in to the ground in leaf litter and other sheltered areas in fence rows of your garden plot and waited out the freezing temperatures and the snow.
Adults begin emerging from these protected areas when beans begin sprouting and continue to emerge for up to two months. The adults feed for approximately two weeks before depositing their eggs on the underside of leaves. And when I say feed, I mean ravage.
Yellow eggs 1 mm (1/20 inch) in length are laid in groups of 40-60 on the lower leaf surfaces. Females may deposit an egg-mass every two to three days. Eggs hatch in 5-24 days. Immature larvae are yellow and are covered with large spines. Larvae feed for two to five weeks before pupation.
You have 3 chances to kill these beetles off – crush the eggs, crush the larvae and crush the mature beetles. The first two are the easiest but you can catch and kill the beetles too. You just have to be persistent. If you can make it through July and August, when the greatest amount of injury occurs and the adults begin to disappear, you might save some of your bean harvest.
Green Bean Diseases
Green beans can fall victim to some of the typical, soil and air borne diseases like bacterial spot, bacterial blight, Anthracnose and powdery mildew and a few I never heard of like Cercospora leaf spot.
Bottom line, I have not experienced one of these diseases in my garden. Maybe I’ve been lucky. Maybe I rotate my crops properly and buy seed that is resistant to bacterial infections. And just maybe, my climate helps me along.
In any case, if you want to know all about raising green beans and managing the multiple diseases that might just affect your plants, check out the 12 diseases that are included in one of the most comprehensive guides to growing green beans I have ever read.
Then take a chance and plant some beans. They grow fast. They set tons of beans. If you plant them properly, train them right (if they’re pole beans) and aggressively crush all variations of the Mexican Bean Beetle, you will be able to harvest and enjoy green beans all summer long.
My Harvest Trick
I said I had one and I do. I plant enough green beans in my garden to satisfy the need for fresh green beans on the table all summer long. But I’m a pragmatist with a limited amount of growing space.
So, when I’m ready to can green beans for the winter, I visit my favorite Amish farmer and buy as bushel and a half of beans and start cleaning, trimming, packing and pressure cooking green beans.
NOTE: You MUST pressure cook green beans to preserve them. You CANNOT simply water bath them. Why not?
Green beans are not acidic.
According to the USDA’s Complete Guide to Home Canning and Preserving, (my favorite guide), green beans must be heated, under 10 pounds of pressure for 25 minutes (for quarts) to make sure you kill all bacteria including Clostridium botulinium, the cause of botulism, a life-threatening disease.
Fresh or canned, I love green beans and I love everything about growing them except the Mexican Bean Beetles.
RECIPE: Roasted Green Beans
1 pound green beans, ends snapped off
1 tablespoon olive oil
Kosher or large grain salt to taste
Fresh ground pepper to taste
Preheat oven to 450 degrees. This is the most important step.
Line baking sheet with aluminum foil or parchment paper.
Spread beans on baking sheet and drizzle with oil.
Toss with both hands to coat beans with oil, evenly.
Sprinkle lightly with salt and pepper.
Roast for 10 minutes. Remove baking sheet from the oven and flip beans over.
Roast for another 10 to 15 minutes.
Next week, I’ll share my own experience with trying to grow dried beans and what I discovered about growing, harvesting and eating dried beans.
Lots of good information! We did very well this past summer with organic green beans — the bush variety — grown from seed. But I’ll refer back to this post next year if we start to see signs of beetles or other problems. The canning info will also be helpful!
I’m so glad you like the information. I love sharing what I have learned the hard way and getting tips from other gardeners. Have to confess I’m jealous of the island with no Mexican Bean Beetles….hope it holds.