In the Garden:
Northern & Central Midwest
August, 2000
Regional Report

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Rudbeckia nitida 'Herbstsonne' in my garden.

South of the Border Beetles

I walked into the soybean field that adjoins my garden the other day and was thrilled to see ladybug larvae and adults all over the beans. They were feasting on the burgeoning population of aphids. I was happy about the ladybugs until I started looking more closely. Some ladybug look-alikes were eating holes in the leaves!

Identifying Mexican Bean Beetles

I pulled out the books and found some clear pictures of ladybugs and their look-alikes, Mexican bean beetles. Mexican bean beetles are a little more oblong, they have exactly 16 black spots on their wings, and they have a red or orange thorax (the segment between the back and the head) with no spots on it. Ladybugs have a black or spotted thorax. Sure enough, my neighbor's soybeans, and my beans, have healthy populations of both beetles.



Beetle Removal

I've had absolutely no problems with my beans this year, aside from the early spring slug damage. I've never even seen a Mexican bean beetle in our area before. Now my bean leaves are full of holes, and even though it's nearing the end of their season, I'm going to have to pull my beans out to prevent the beetle population from getting too high. The bush beans have finished producing, but the heartbreaker is my asparagus beans that are just coming into production.

Beetle Trap Crop

And here I thought the soybeans would be a trap crop. They ended up being a nurse crop instead! At least the farmer who owns the field does a healthy rotation, so the field should be in wheat next year. Without the soybeans, I hope the Mexican bean beetles will go elsewhere. Just in case, I'll be ready to pick them off next year.




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