Armyworm Invasion Hits Laurens County: What You Need to Know

The Extension Service has been receiving reports of Fall Armyworms South Carolina for some time.  Recently we began seeing them in Laurens County in forage and hay crops, just last week we also began receiving calls about armyworms in some lawns in the area.

Armyworms do not over-winter in South Carolina, but instead spend the winter on the Gulf Coast.  In the summer they begin moving North, eating and multiplying as they move.  Over time they reach South Carolina, and in many years they will eventually reach Laurens County.  We do have armyworms most years in our county, but many times the numbers are small enough to be of little real concern.  This year, however, the numbers are large enough to cause problems, and with multiple life cycles in a year meaning another “wave” of armyworms will be in the area in September, some caution and scouting is justified in the field and in the lawn and garden.

According to Clemson Entomology, Soils, and Plant Sciences Department factsheets, the favorite foods of the fall armyworm are native grasses such as Bermudagrass and Johnsongrass.  Crab grass seems to fall into this category also.  When the armyworms exhaust their preferred food source, they will move to other sources, such as fescue and some vegetable or field crops.  The greenish or brownish caterpillars grow to one and one-third inches long, and can be identified by an inverted “Y” on the head and three yellowish-white stripes down the back. There is no preventative treatment for armyworms, since their adult stage is a flying moth.

Many of us will not see any armyworms in our lawns this summer. If you should find an armyworm in your lawn, don’t panic!  These creatures cause damage when they are present in large numbers.  Two or three in the lawn is not a cause for immediate action, but a reminder to keep an eye on things daily.  The time to treat for armyworms in the lawn is when you find three or more 0.5 inch or larger armyworms in a one square foot area.  There are several good treatment options for the home lawn that work well on them and are labelled for use in the lawn.  Follow label directions of the insecticide if used to ensure proper, safe application.  Clemson’s Home and Garden Information Center has an armyworm factsheet with insecticide recommendations:
https://hgic.clemson.edu/factsheet/armyworms/

Image credits: ​

• Clemson University CE Series 42-2931C.
• ​​Armyworm Damage 1 sm.jpg: Bryan Smith
• ​​Armyworm Damage 2 sm.jpg: Bryan Smith