How to Control Mexican Bean Beetles

August 29, 2012 by  
Filed under Beans, Blog, Insect Problems

Wednesday 8-29-2012

I have been harvesting quite a few yellow wax beans these days, but I have also noticed quite a few Mexican bean beetle larvae feeding on the bean leaves, flowers, and the beans themselves. The damage has not been too bad, but I do get some bean damage on every 5th bean or so that I pick.


Mexican bean beetles feed really like legumes such as beans, peas, and soybeans. They will feed on the leaves, stopping at the veins leaving just the veins.   


Mexican bean beetles are actually members of the lady beetle family. I would consider them the black sheep of the family. The adults look a lot like large lady beetles, with eight small black spots on each wing.  The larvae are yellow and covered with spines. The adults lay tiny yellow eggs in clusters on the underside of leaves close to the ground.


Control Measures

1. Plant your beans as part of a diverse polyculture to avoid grocery store aisles for pests.


2. Plant bush beans instead of pole beans and pick pods as soon as they mature. I still get damage to my bush beans, but a little less than pole beans.  


3. Use row covers. I don’t bother with row covers. It’s too much time and effort.


4. Attract or release soldier bugs, and spined soldier bugs. These are the principle predators of the Mexican bean beetle. Provide a diverse habitat with many flowers and your predators will eventually show up.


5. Insecticides can be applied according to label directions, but I would not spray pesticides, as this will just drive away the soldier bugs that will come to your rescue.


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