BLACKSBURG, Va. — In his more than 20 years at Virginia Tech, this is the worst season for fall armyworms that Tom Kuhar, a professor of entomology, has ever seen.
Fall armyworms are the larvae of tropical moths native to warm climates of the western hemisphere. Female fall armyworm moths can lay up to 1,500 eggs in their 31-day lifetime, creating a vast number of larvae that feed on grass. A large population of armyworms can severely damage a lawn, consuming all the grass in their path.
Across the commonwealth, gardeners and community members are encountering more fall armyworms than ever, as the high number of early named storms in the Atlantic has pushed currents of warm air — and moths — north into Virginia.
“This year, the moths arrived as early as we might see them,” said Kuhar, who began to get reports of fall armyworm outbreaks in Richmond during the last week of August. These worms were likely brought to Virginia on storm fronts in mid-August.
Once here, moths brought by these warm air currents can lay eggs and reproduce quickly, creating many worms in a short period.
“This year we may even see a third generation of fall armyworms in Virginia,” said Mike Goatley, Virginia Cooperative Extension turfgrass specialist and professor of turfgrass science. “Fall armyworms can keep completing their short 31-day lifecycle and laying eggs until we get the first killing frost.”
“If we get another tropical system that pushes the moths north again, who knows how many more we could see,” Goatley said.
Spodoptera frugiperda, commonly known as fall armyworms, feed on turfgrass, consuming leaves with their chewing mouthparts as they move across the lawn. Their presence is often indicated by increased bird-feeding activity. When present in large numbers, these destructive pests can defoliate lawns, eating all the leaves off of turfgrasses.
In cases where minimal leaf thinning has occurred, fall armyworm damage on cool-season grasses can be remediated with a standard recommended fall fertility program. Gardeners who encounter high populations of fall armyworms in their landscapes can also consider chemical treatment. To appropriately fertilize your fall lawn by getting a soil test to measure nutrient levels and pH or for specific pesticide recommendations, contact a local Extension Office.
If fall armyworms have severely damaged the grass, it may be necessary to replace grass with fall seeding or sodding. Late summer to early fall is always a great time to establish a cool-season turfgrass, such as Kentucky bluegrass or fine-leaf fescues. For more information about fall lawn care and effectively seeding a lawn, see Extension’s publication on fall lawn care.
If interested in learning more about turfgrass maintenance, Virginia Cooperative Extension Master Gardeners can help. Master Gardeners bring the resources of Virginia’s land-grant universities – Virginia Tech and Virginia State University – to the people of the commonwealth. Contact local Master Gardeners through an Extension office or click here to learn more about gardening in Virginia and the Virginia Extension Master Gardener program.
–Devon Johnson, Virginia Tech