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Don’t give up growing beans these tips for Mexican bean beetle control will help you get rid of them in your garden organically.
Mexican Bean Beetle Control
Mexican bean beetles can cause so much damage in your garden.
Have you ever gone out to your garden and seen that your bean leaves have a lot of holes in them? Perhaps the leaves are gone except for the veins?
That is a sure sign that you’re dealing with Mexican bean beetles. These bean beetles are in the same family as ladybugs and look quite similar. But unlike our beneficial ladybugs, these bean beetles are a real pest in the garden.
Mexican Bean Beetle Description
The adult Mexican bean beetles are a small 1/4 inch oval-shaped insects. It’s yellowish to copper brown in colour with 16 black spots on its wing covers.
The larva of the Mexican bean beetle is a fat grub 5/16 in long, yellowish-orange in colour with long spines.
The eggs of the Mexican bean beetle are small yellow ovals that are laid on the bottom of leaves.
Mexican Bean Beetle Life Cycle
The adult Mexican bean beetles overwinter in the leaf litter and other debris left in gardens and nearby fields. In the spring the females lay their eggs in clusters on the beans.
The eggs hatch 5 to 14 days later and the larva begins to feed on the bean plants. They will feed for 2 to 4 weeks before pupating on the underside of the leaves.
Mexican Bean Beetle Damage
Both the larva and adult beetle are damaging to bean plants.
They can sometimes be hard to spot because they feed on the underside of the leaves. But you will recognize the damage right away.
Their feeding creates a lacy appearance to the leaves. With enough feeding the leaves of bean plants looking like skeletons. This will stress the plants and lower yields. If the damage is bad enough the plants may be killed.
On the bean pods, you will see round holes caused by their eating. They often will look brown or black if they have scabbed over. The damage really makes the bean pods look bad. It’s also very hard to cut around all the bad spots to save what is left of the bean pod.
Controlling Mexican Bean Beetles Organically
Although the Mexican bean beetle is a nasty pest in the garden there are many natural ways to control them.
One way to minimize the loss of bean crops is to plant early season bush beans so that they have matured and produced before the peak of the Mexican bean beetle cycle.
Use Trap Crops
Mexican bean beetles love soybeans. You can use this to your advantage by planting a small patch nearby.
Once they have infested the soybeans destroy the crop. You can pull the plants and bag them to dispose of or burn.
Cover With Floating Row Covers
If you practice crop rotation with your beans, one good method of preventing Mexican bean beetle damage is to use floating row covers.
As soon as you have planted your bean seeds cover the bed with the row cover. Leave it on until the plants are large enough to stand up to the damage.
Handpicking can be the best option for small gardens. Every day or two, walk through your bean patch and check the undersides of the leaves for Mexican bean beetles, larva, and eggs. Squish the egg clusters with your hands and scrape the larva and beetles into a jar of soapy water.
If you keep this up it’s an excitant way to keep your beans pest-free without using chemicals.
Soldier bugs (Podisus maculiventris) and parasitic wasps (Pediobius foveolatus) are natural predators of the bean beetle larva. You can buy and release these into your garden early in the season as soon as you see the eggs under the leaves.
Ladybugs and lacewings are also predators of the eggs and larva of bean beetles.
Mexican bean beetle damage is often the worst in fields and gardens that don’t have a variety of plants and flowers growing.
Purposefully growing a wide variety of plants in your garden encourages beneficial insects and helps to repel pests.
Try planting marigolds, nasturtiums, petunias, and rosemary to help prevent Mexican bean beetles in your garden.
Organic Insecticides For Mexican Bean Beetles
There are a few organic sprays you can use on your bean plants to get rid of pests.
Btk (Bacillus thuringiensis) is a natural bacteria found in the soil that is very effective for killing caterpillars.
This will help to kill the larva of the Mexican bean beetle but won’t work on adults. The downside is that they have to eat leaves that have been sprayed with Btk it doesn’t work on contact with their skin.
Spraying the plants every 2 weeks will help to control your bean beetle problem.
Neem oil is another effective way to get rid of pests on your plants.
Apply the neem oil as a foliar spray in the evening. The 2 main reasons for spraying it in the evening is to avoid burning your plants leaves. Spraying any oil on leaves in full sun is a bad idea.
When you spray in the evening it will be dry by morning. This is safer for your leaves and also means insects that chew the leaves will be affected.
Insecticidal soap can also be used for bean beetle control but it has to be sprayed directly on the larva to have an effect.
Diatomaceous earth can be spread on the ground around the bean plants. You can also dust the leaves with it. It’s a very effective way of getting insects off your plants. You can read about how I use it to get rid of cucumber beetles and use a similar method for bean beetles.
The most important thing when dealing with Mexican bean beetles or any other pest in your garden is to be diligent. Consistent removal of the pests by hand and/or application of natural treatments will go a long way to helping you have a healthy and productive garden!
Kim Mills is a homeschooling mom of 6 and lives on an urban homestead in Ontario, Canada. Blogging at Homestead Acres she enjoys sharing tips to help you save money, grow and preserve your own food.