Time to Scout Your Pasture

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I have received numerous phone calls over the past few weeks about armyworms in hay fields and pastures in Lee County. There are two types of armyworms that we scout for in grasses. These are true armyworm and fall armyworm. True armyworm can be easily identified by the orange stripe running down both sides of its body. True armyworm is typically a spring time pest in cool season grasses such as fescue.

Fall armyworm is the most common type of caterpillar pest in North Carolina pastures. Fall armyworms are identified by green, brown or black stripes running the length of the body with darker stripes along its sides. Fall armyworms also have a pale colored upside down “Y” marking on the head. For help with identification, please contact me at my office.

The fall armyworm is a common chronic pest in the Southeastern US. This pest can cause severe damage to forages and grasses, including turf. Grass and forage species affected by fall armyworms include bermudagrass, fescue, ryegrass, alfalfa, sorghum sudangrass, corn and small grains. Damage often times goes unnoticed until heavy feeding occurs, resulting in fields turning brown, resembling drought damage.

Fall armyworms in North Carolina most likely overwintered in Florida and migrated north throughout the warm weather months, during the annual moth migration. Female moths can lay as many as 1,000 eggs, which hatch within 2-10 days. Once hatched, the larvae feed on the remaining egg mass and finally drop to the soil surface to begin searching for food. In heavy infestations, caterpillars can consume all of the available foliage and crawl in “armies” to new grass or forage stands. The larvae will feed for 2-3 weeks before digging into the soil to pupate. 2 weeks later, a new moth population emerges. Several generations occur in North Carolina each year with early infestations following a mild winter.

Fall armyworms are unique from other caterpillars in that they feed day and night, but are most active at night. Scouting for this pest is best done early in the morning or late in the evening when the larvae are most active. Fresh caterpillar damage is most noticeable in the morning. Scout along the tree line of your pasture and work your way to the center of the field, looking for brown patches where damage to the foliage has occurred. If there are more than three ½” long larvae per square foot, treat your pasture.

Be mindful of caterpillar length when scouting. Larger caterpillars (1.5”) have done most of the damage that they will do in their lifetime. If hay is ready to mow and bale, you may be able to bale the hay and not treat, if a majority of the caterpillars are 1.5” in length.

I have also had a report of a chinch bug infestation in the western end of the county. This is not typically an insect that we scout for in hay fields and pastures, almost exclusively a turf pest. However, high populations were observed and adequate control was achieved was following an insecticide application. For more information on how to control fall armyworm in your pasture and hay fields, please contact me or your local farm supply dealer.

If you have any questions relating to field crops, livestock, pesticide credits or general agriculture, feel free to stop by my office located at 2420 Tramway Road or contact me at 919-775-5624.

Mitchell Williams is the Field Crops and Livestock Agriculture Agent for North Carolina Cooperative Extension in Lee County.