Fall Armyworm, Vol. 8, No. 9

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May 10, 2022

Spodoptera frugiperda

Order: Lepidoptera
Family: Noctuidae

Fall armyworms are sporadic pests of bermudagrass throughout the state. “Sporadic” means they are worse some years than others. They are sporadic because they don’t overwinter here. The moths must fly in from more southern regions each year, and the populations we have here depend on when they arrive, how many arrive and the weather conditions they experience once they get here. Last year all these factors aligned to produce an unusually heavy and far-reaching outbreak, the largest and most widespread outbreak I have seen in my 34-year career. Will they be back this year? They will. We have some fall armyworms in the state every year, especially in hayfields in the southern part of the state. Will they be as abundant and widespread as they were last year? Probably not. The odds of having two such heavy outbreak years back-to-back are small, though there is that small possibility. Fall armyworms damage bermudagrass in a lot of different situations, both agricultural and non-agricultural: hayfields, pastures, home lawns, commercial landscapes, golf courses, and sports fields. Bermudagrass is their favorite, but they will also attack other grasses, such as bahiagrass, broadleaf signal grass, millet, rice, Sudan grass, sorghum and corn. Sometimes they even damage broadleaf crops like soybeans and cotton. They are called fall armyworms because populations are highest in late summer and fall, but they usually complete several generations here, with damaging infestations occurring as early as June during outbreak years. How can you keep fall armyworms from causing heavy damage to your hayfield or turfgrass this year? Be ready for them! Check your hayfields or bermudagrass lawns and turf regularly and be prepared to treat promptly once you detect an infestation. Have your sprayer cleaned up and ready to go and have an effective insecticide on hand—or be able to get it on short notice, so you don’t have to spend time getting ready to spray once a damaging infestation is detected. It only takes a couple of days for a heavy infestation of large fall armyworm caterpillars to turn a promising cutting of hay into a field of stems. See Extension Publication 2717, Fall Armyworms in Hayfields and Pastures , for a list of recommended insecticides, application rates, pre-grazing intervals and pre-harvest intervals on forage crops. Information on scouting and thresholds is also included. See Page 8 of Extension Publication 2331, Control Insect Pests in and around the Home Lawn . for information on do-it-yourself armyworm control in home lawns. For smaller lawns, one of the cheapest, easiest, and most convenient ways to treat is to use one of the ready-to-use hose-end applicators that contains a pyrethroid insecticide, such as permethrin, cyfluthrin, bifenthrin, or cyhalothrin. For large lawns, one of the easiest and most convenient ways to treat is to hire a licensed commercial applicator. But if you have the right equipment, you can do your own spraying. See Pages 12 and 13 of Extension Publication 1858, Insect Control in Commercial Turf, for information on fall armyworm control in sports fields, golf courses and other commercial turf. Before treating sports fields be sure to verify the product you plan to use is specifically labeled for use on sports fields and carefully check the re-entry interval. See Bug's Eye View No. 7 of 2021 for a short article on “gas can beetles” and a good example of why it is important to check your sprayer and make sure it is ready to go well before you might need it.

Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service. The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled. Mississippi State University is an equal opportunity institution. Bug’s Eye View is now on Facebook. Join the Bug's Eye View Facebook group here.