Until we know more about bean leaf beetle flight patterns in SD, the best way to manage this insect is by regular monitoring of the field. Management decisions must be based on actual injuries observed on the plants at any given time, and not on some predictive recommendations developed from historical data by our neighbors to the east and south. Bean leaf beetles can damage soybeans by defoliating the plants, and by feeding on and clipping the pods. Economic thresholds are available for both types of damages and may be used whichever is most important on the field at the time of scouting. Defoliation will be less important when the leaves start turning yellow.
Pod feeding by the beetles also becomes less critical once the pods themselves turn yellow.
Remember that pods tend to stay green after the leaves have changed colors. And bean leaf beetles will feed on any green soybean tissues. You may also contact SDSU Extension Entomology to obtain a free printed material. These thresholds are based on the injuries caused by bean leaf beetles on soybean pods. Expected yield is 45 bushels per acre.