Answer: Did you see the worms? Sounds more like Mexican Bean Beetle which is a serious pest on beans. The adults are yellowish beetles, similar in size and shape to "Ladybugs" with 16 black spots on their backs. Larvae are fat, yellow grubs with long, spines. Yellow egg masses are on the undersides of leaves.
Good control can be obtained in a small garden by using floating row covers. Also earlier plantings are usually less bothered by the beetles. Handpick (or hand squish as I usually do!) the bugs. Check and eliminate egg masses on undersides of leaves. Soybeans planted nearby can be a "trap crop" since they are favored food. Use neem or pyrethrins as a spray if necessary. Always rotate crops at least every other year!
Consider adding organic matter, such as compost or leaves to your soil. Soils rich in organic matter are healthier and produce healthier plants that are able to resist pests and disease.
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