Every year lawns and pastures become targets for late summer grass eating caterpillars. It’s important to watch for these pests and begin treatment as soon as possible.
Fall armyworms show up like clockwork, causing significant losses to grasses when not managed properly.
Jay McCurdy, turfgrass specialist at Mississippi State University, says fall armyworms typically appear when nighttime temperatures first begin to drop; an event usually marked by the first significant rainfall that breaks the late summer drought.
“Fall armyworm damage appears when turf yellows or browns out quickly, from within hours or a day or two,” McCurdy said. “Upon closer inspection, there will be insect larvae crawling while feeding on the leaf tissue.”
Damage often appears first as a circular region of stricken turf and the damaged areas can expand quickly as the insects move.
Extension forage specialist Rocky Lemus says that despite their name, fall armyworms can be a problem beginning in late spring, but are more prominent in late summer and early fall. “Armyworms are a very destructive pest of forage crops, especially in annual grasses like crabgrass, forage sorghums, and pearl millet; as well as in bermudagrass and legumes such as alfalfa,” Lemus said. “Bahiagrass is not a preferred forage crop for armyworms.”
Armyworms have five growth stages, and it is not until later stages that the caterpillars begin consuming large amounts of forage and causing the most damage.
“Armyworms like to feed in grasses with leafy material and high sugar concentrations,” Lemus said. “They can remove leaves in a matter of hours when there is a high infestation, leaving only the stems. Remaining forage develops brown spots that resemble drought damage.”
“Clients will call asking about their lawns looking bad, and they comment that overnight it went from looking really good to looking really bad,” Lemus said. “There is a lot of truth to it, as these worms can do damage very quickly.”
Effective treatments for these caterpillar pests are readily available, but finding the insects early is a key component. Lawns and pastures are able to recover following treatment, but it sometimes takes until the next growing season for the damage to completely disappear.
Caterpillars moving into lawns and pastures
