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Posts Tagged ‘bean insects’

Every family has them – the bad apples of the bunch.  A cousin that gets rowdy at parties or a sibling that seems like a lost cause may have us shaking our heads, tut-tutting while whispering “well, you can pick your friends but not your relatives.” 

So it should be no surprise that even lady beetles, the beloved icons of the garden, have a skeleton in their closet.  Well, actually, they have a lot of skeletons in the closet and they’re all leaves, thanks to the feeding habits of the Mexican bean beetle (Epilachna varivestis). 

Adults resemble large lady beetles, being rust colored with 16 spots on their backs.   But the larvae are like rock stars:  bright yellow and covered in huge spines. 

This bad bug feeds on the undersides of leaves of beans and soybeans, rasping off the green tissue and leaving  lacy, skeletonized remains.  If enough beetles gather for a food fest, beans and stems can be attacked and destroyed.

Adult beetles over-winter garden debris, emerging from when beans sprout through mid summer. Eggs are laid on the underside of leaves in clusters containing up to 60 eggs, hatching in one to three weeks.   Larvae then feed for two to five weeks.  There are several generations per year.

July and August are when we see the most damage, so scout your plants for signs of the critters.  Control them by hand picking and dropping them into a bucket of soapy water, or if you’re a bit squeamish about squishing, spritz the larvae with insecticidal soap.  Meticulous cleanup of the garden in fall is a must for keeping these pests from overwintering in your yard.

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