By ALICIA BOOR
Cottonwood Extension District
Though often found in agricultural crops, fall armyworms have been found in certain turfgrass species and we’ve had many reports of them recently. This has been a bad year for them in crops as well as in homeowners’ turf.
Description: Young larvae are ½ to ¾ inches long. Mature larvae can reach 1½ inches long. Fall armyworms can be identified by the inverted “Y” on top of the dark head. Adult moths are ½ inch long. The two front wings are brown-grey. Males have more dark markings than females.
Life Cycle: As a tropical insect, fall armyworms are not able to overwinter in Kansas limiting them to 2-4 generations each year. Moths migrate to their seasonal home and lay hundreds of eggs in clusters. Larvae hatch and begin feeding. Once established, new generations can occur every 23-25 days.
Damage: Larvae feed on grass blades. Heavy infestations will occasionally chew the blades to the crown. Though the damage may be unsightly it does not typically kill the grass. Regrowth of the turfgrass can be expedited with rain and/or irrigation.
Control: If insecticide applications are considered, cyhalothrin (Spectracide Triazicide), permethrin (38 Plus Turf, Termite & Ornamental Insect Spray; Hi-Yield Garden & Farm Insect Control; Eight Yard & Garden RTS) and spinosad (Conserve, Monterey Garden Insect Spray, Captain Jack's Dead Bug Brew, Natural Guard Spinosad) and Dylox (BioAdvanced 24-Hour Grub Control) are commonly available materials registered for control of fall armyworm in turf. Neem oil is also an option if a homeowner does not want to use chemicals.
Spray treatments have greater and quicker contact efficacy than granular applications. Granular treatments require irrigation or rain to activate the insecticide from the dry granular carrier. Professional lawn care service personnel have access to additional materials (such as Scimitar and Deltamethrin) which may have more persistence than homeowner products.
Alicia Boor is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact her by e-mail at [email protected] or calling 620-793-1910.