By Lucy Ray, Morgan County Extension Agent
They’re back! We officially have armyworms here in Morgan County again this year. In addition, they are turning up in Newton and Jasper counties. In late summer and early fall, armyworms invade pastures, hay fields, and turfgrass throughout the state. Fall armyworms feed on a variety of forage crops, but seem to prefer lush, green, well-fertilized Bermudagrass. Hayfields are particularly at risk. Other forage crops such as tall fescue, pearl millet, sorghumsudan hybrids, bahiagrass and various winter annuals including ryegrass, wheat, rye and oats are also attacked. Please remain vigilant! Check your hayfields and pastures regularly. Keep an eye out for unusually heavy populations of birds in your fields, unexplained “greasy-streaks” in the road, and wet/greasy four-wheeler tires on an ordinarily dry day! If you have any Fall Armyworm pressure, please let the Morgan County Extension office know. Particularly in pastures and hay fields, damage may be severe before the worms are noticed. Armyworms will not kill the grass, but hay and forage yield can be reduced to almost nothing over whole fields in extreme cases.
Scouting pastures and hayfields can help detect fall armyworm infestations before they cause economic damage. Therefore my advice is for forage producers to scout pastures and hayfields regularly from now until frost. Scouting for fall armyworms is a relatively simple process. Walk into the pasture from all four sides or walk in an X pattern across the field to make sure you check a large enough area. Stop at about 10 places in the field, and look closely for small caterpillars feeding on the grass. If you find them, estimate the number of armyworms per square foot.
Pastures should be treated for armyworms when the number of larvae per square foot is more than three. There are several pesticides that are labeled to treat armyworms in pastures and hayfields which include Sevin, Baythroid XL, Lannate, Dimilin 2L, Karate, Prevathon, and Mustang Max. Restrictions on these pesticides vary with the product. For example, pastures sprayed with Lannate cannot be cut for hay within three days of application or grazed within seven days of application. Lannate should be used on Bermudagrass pastures only. Mustang Max and Baythroid XL have a zero day post-harvest interval. Dimilin has a zero day post-harvest interval for grazing and a one day post-harvest interval for hay. Pastures or hayfields sprayed with Sevin (carbaryl) cannot be grazed or harvest for 14 days following application. Chlorantraniliprole (Voliam and Coragen) have a zero day post-harvest interval for grazing and a seven day post-harvest interval for hay. Prevathon has a zero day post-harvest interval for both grazing and haying. As always, be sure and follow the label directions of any pesticide that you use.
In turfgrass and yards, if there is any doubt about whether worms are present, pouring soapy water on the grass (1/2 oz. dishwashing soap/gallon water) will bring them up very quickly. Heavily infested turf will also have visible greenish-black fecal pellets on the soil surface. Other indicators of armyworm infestations may include birds or even paper wasps that use the fall armyworms as food. Armyworms are most active late in the day and at night, so pesticide applications should be made as late as practical for best results. Cutting the grass prior to application may improve control, but do not cut grass for one to three days after application.
If you find armyworms in your yard, pasture or hayfield, or if you have any questions about treating them, please call the Morgan County Extension office 706-342-2214.