In the Furrow
Will Fall Armyworms Attack the Hay Crop?
By Will Duffie County Extension Coordinator

The fall armyworm is a chronic pest in Burke County. Female moths lay eggs and in 5 days small caterpillars will be feeding on a variety of forage crops, but they seem to prefer lush, green bermudagrass. Don't be mistaken, they will feed on other forage grasses such as bahiagrass, millet, and many other forage grasses.

Fall armyworms are most numerous in late summer or early fall. Usually, reports of fall armyworm damage begin to come in during late July or early August. What normally happens is someone will report that their hay field has been completely eaten, and they will be right. After the initial loss, fields will then be scouted.

Several means are available to detect fall armyworm levels. The first is to scout fields on a weekly basis. Check down in the grass for larvae feeding. Another technique is to catch adult male moths with traps. We are in the process of locating several traps around hay fields in Burke County. Call if you are interested in checking a trap daily.

These armyworms are typically most active early in the morning and late in the afternoon, but on taller, unmowed grass, they can be observed feeding on foliage throughout the day. On closely grazed or recently mowed hayfields, fall armyworm larvae spend the warmer hours of the day deep in the sod.

Remember that young armyworms don't eat much. Most of the damage is caused by the oldest caterpillars which eat more than all the other ages put together. In closely grazed fields, the grass may seem to thin out and develop brown spots. In hayfields or in pastures where there has been substantial growth, all tender green material may be removed, leaving only tough stems.

The decision to treat for fall armyworms depends on the stage of the armyworms and the intended use of the forage. A population of 3 or more fall armyworms per square foot is a reasonable treatment threshold. If necessary, treat with insecticides at the right time. Small fall armyworms are much easier to kill than larger ones.

If insecticidal control is necessary on perennial grass pastures and hayfields, formulations of Sevin, Dimilin, Lannate, and Tracer are recommended. Pay close attention to grazing and harvest restrictions. Apply insecticides early or late in the day, because fall armyworm larvae are most active at these times.

Contact the Burke County Extension Office at 706-554- 2119 for information on insect control in hay fields and pastures.