–by Jeff Whitworth — Field Crops
2021 might be called the “year of the worm”. Starting in late winter/early spring, 2021, there was considerable activity by army cutworms. Most of the problem was caused by the larvae decimating thin strands of wheat and/or alfalfa. Then, since late spring/early summer, a combination of armyworms and fall armyworms have been causing serious concern and damage in lawns, pastures, and alfalfa fields throughout about the eastern 2/3rd’s of the state. Army cutworms spend the summer in the Rocky Mountains but start to migrate back into Kansas in early fall every year. The larvae may feed on just about any plants but mostly affect wheat and alfalfa, as these are usually the only plants actively growing this time of year. Armyworms, probably more so than fall armyworms, may continue to cycle through another generation or even two as they overwinter in Kansas, and thus it will probably take a “hard” frost or freeze to stop them. Fall armyworms, since they don’t usually overwinter in Kansas, may migrate south after this generation become adults-but there could be another, or at least partial generation. Armyworms infest primarily grasses, i.e. sorghum, corn, brome pastures, lawns, and often this time of year, wheat, but occasionally alfalfa, etc. Thus, if armyworms are the problem they could be around through another generation or maybe even two depending upon the weather. So, if armyworms are relatively small (see pic 1) they will probably feed for another 10-14 days then pupate (stop feeding). If they are relatively large (see pic 2) however, they will probably pupate in the next 3-7 days. There will probably be at least one more generation of armyworms. Fall armyworms (see pic 3) have a little wider host range, which includes alfalfa, soybeans, corn, sorghum, wheat, etc., but don’t usually overwinter in Kansas, thus, hopefully, will be heading south after these larvae finish feeding and become moths. Also, in the next 30-60 days army cutworm moths should have returned from their summer Rocky Mountain retreats to deposit eggs throughout at least the western 2/3rd’s of the state and thus, these tiny worms will start feeding on wheat and/or alfalfa all winter.
Picture 1: Small Armyworm (pic by Cayden Wyckoff)
Picture 2: Larger Armyworm (pic by Cayden Wyckoff)
Picture 3: Fall Armyworms (pic by Jay Wisbey)