I’ve received several phone calls over the past few days about threecornered alfafa hoppers in V-stage beans. Many of the questions are related to the recent cotton injury that was observed in West TN where cotton was planted behind a legume cover crop. Hopper injury in beans is not the same as hopper injury in cotton. Hopper injury in seedling (less than 6 nodes) cotton often results in a girdle on the main stem. Over time the girdle swells, the cotton stops growing, the leaves turn red and the cotton dies.
Hopper injury in beans results in a girdled main stem, when plants are less than 8-10 inches tall, that doesn’t result in plant death like cotton. Girdled beans are at increased risk for lodging late season when neighboring plants don’t have time to compensate. Yields of girdled plants won’t be affected unless they break over during the season. Hopper damaged beans tend to be worse in thin stands and poorly growing soybeans. Hoppers are typically easy to control with pyrethroids or acephate. Insecticide seed treatments provide some protection against hoppers during the seedling stage, although levels of protection can be highly dependent on environmental conditions. For more information on thresholds and control options please visit: https://guide.utcrops.com/soybean/soybean-insect-guide/threecornered-alfalfa-hopper/