Mexican bean beetle larvae

Mexican bean beetle larvae can and will destroy your whole crop. They proliferate exponentially.

Perhaps you like me have been scared by all the research coming out linking red meat to cancer, and have made the decision to increase the legumes in your family's diet.

What's not really clear is how much of this scare is related to the hormones and antibiotics that are used on cattle.

Mexican bean beetle damage

This page was last updated by Bernard Preston on 1 January, 2019.

Certainly processed meat like bacon, many sausages, hot dogs and ham should be kept for high and holy days. It's one of the biggest beefs that I have with the banting diet; all that bacon is certainly not a healthy choice food.

So we planted out out beans by the million, pole and bush; the climbers are definitely better for my money, but unfortunately the Mexican bean beetle larvae also think so. For several years we had no problem, and then I started noticing holes in the leaves. Finally they started to look like someone had used a shotgun and all that was left was the veins of the leaf. Then attacked the beans themselves, leaving them covered with black bite marks.

Mexican bean beetle larvae

Mexican bean beetle larvae are mean little insects undermining all your efforts to increase your dietary vegetable protein.

The damage seems to be worst right in midsummer. That means December and January in the very deep south, but of course July and August in the States. For the moment they don't seem to have touched the lima beans.

I wasn't sure whether it was chafer beetles or the Mexican bean that was doing the damage, until I caught one with his hands in the till. I've been watching out for them, but they feed at night and seem to be quite astute and then vanish during the day.

Then finally I spied what appeared to be a yellowy orange beetle, rather like a ladybird, but considerably larger squatting on the underside of the leaf right over a large hole where it had eaten away the foliage. What was note worthy was the black spots on its back; 16 of them I'm told but I was more concerned to squash the beast than count its dots.

Mexican bean beetle

First they chomp the leaves, and they attack the fruit, ruining the crop. Pick the beans when they are very young.

Mexican bean beetle fruit damage

The beetle itself is almost oval in shape. It lays about 50 yellow eggs of the underside of the leaf which hatch in about a week; the plump Mexican bean beetle larvae are about 8mm long with rows of fuzz down running down their backs.

The larvae feed on the leaves for a few weeks before pupating, the adult form of the beetle cycle emerging about a week later.

They live about two months; there are several cycles of beetle to egg, to Mexican bean beetle larvae and pupating back to the adult stage.

So, one beetle laying 50 eggs, would produce another 50 adults laying 2500 eggs, each turning again into beetles which lay another 50 eggs. So, in theory one beetle could produce over a million larvae in one season. Little wonder they are so damaging.

Then they return to the ground where they burrow into the soil for the winter.

For a more detailed page on the bug, you can go to pest problem solver.

Oh, dear for several seasons we thought the hens had solved the problem, but they're back. If any of you out there have a solution, please respond at the bottom of this page.

Growing green beans

Growing green beans is not difficult but whenever you have a high quality food, you'll find there are numerous predators. The Mexican bean beetle is just one of them. The monkeys in our neighbourhood also love them, but the paintball gun keeps them at bay.

When growing green beans you must take into account that you will almost certainly have an attack by these pesky beetles.

I have only three solutions for the Mexican bean beetle larvae; one is a partial idea, and the other two as yet are untested, but I think will work.

After two seasons of being decimated by the Mexican bean beetle and larvae, instead of planting a row of beans, I planted them in amongst a row of gem squash.

The large green gem leaves do seem to have significantly confused the beetles; there are far fewer holes in the bean leaves and the fruit itself is not being badly attacked. It's looking like a good crop.

The second is white oil which is a mixture of dishwashing liquid and a light vegetable oil like canola. Both sides of the leaves have to be sprayed, and you must avoid the flowers because it keeps the bees away as well; you'll have poor pollination. It works splendidly well for aphids and white fly on the citrus, and I'm hoping will keep the Mexican bean beetle larvae at bay too.

More here about natural pest management, and another link to growing green beans; certainly one of our most rewarding vegetables.

The third is the chicken tractor which, once the beans are finished will be dragged in place for the chooks to scratch for the adult beetles that are lurking in the soil for the winter. Here is our chicken tractor design. All the bean plants are thrown to the chooks, and they scavenge around the dead leaves and debris under the plants.

On a steel frame, it's mostly electrical conduit and shadecloth, so easy to move.


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Chicken tractor roost in situ

Healthy choice foods

Healthy choice foods certainly means moving gradually away from red meat in general, and processed meat entirely. The alternative is too ghastly to contemplate.

Supplementing our red meat with huge amounts of delicious phytochemical foods is part of our solution; fresh corn on the cob, green lettuce and spicy hot peppers, and so on.

And then for protein looking to legumes to replace our red meat; not entirely. Just reducing our reliance on animal food. But those devil Mexican bean beetle larvae are still being a big hindrance.

I won't spray in our organic garden, so we'll look to natural methods to control the bug. We just love all the delicious healthy choice foods we can grow, straight from garden to the pot before the sugars are changed to starch.

Bernard Preston

Bernard Preston is a semi-retired DC with a passion for healthy living; daily he witnesses the ravages of pain and disability of those who stubbornly refuse to follow the rules.

One of the most important is to absolutely refuse processed meat except perhaps on high and holy days. That means a shift to legumes; the Mexican bean beetle larvae have been a still not resolved threat. We wait and see whether the hens are the solution.

Update: The hens have been a partial solution, but far more effective has been to grow lima and pole beans on the same vegetable garden trellis; actually it's a basic to organic gardening. If one plants all your veggies in a line, the pest simply hop from one plant to the next.

What's your solution to our Mexican bean beetle larvae conundrum? Please contribute any ideas you may have.

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Hilton, KZN

South Africa