The Q&A Archives: Insect chewing small holes in bush beans

Question: Last summer some insect chewed small holes in the pods on my green bush beans. What is it and how do I control it? Ruth Seyller Burbank, IL

Answer: It's most likely the bean leaf beetle, says Chuck Voigt, vegetable specialist at University of Illinois, UrbanA. In midsummer, when fields of soybeans begin to yellow and die, the leaf beetle migrates out of the fields looking for more beans to feedon. Often home gardens are the target, he explains. The adult bean leaf beetle resembles the adult spotted cucumber beetle, but is smaller with more yellow on its back. Overwintering adults emerge in June to begin feeding and laying orange eggs in clusters near bean plant stems. The eggs hatch in 10 days and the larvae and adults feed on bean leaves and young pods until fall. There's one generation a year in the North. The best control in a home garden is to exclude the adult beetles by coveringthe beans with a floating row cover, says Voigt. If some beetles get under the row cover, spray Sevin or pyrethrum weekly at the first signs of damage, he adds. Fall tilling to expose the adults to cold weather and timing your bean planting to harvestbefore midsummer (when the beetles are leaving the soybean fields) will also lessen the damage.

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