Fall Armyworms in Turf

Description

Fall armyworms are approximately 1-1½ inches long, depending on instar, and can vary in color from a green to mottled brown, to almost black (Figure 1). Fall armyworms have wide black stripe running down each lateral (side) of the body. Sometimes, you will be able to distinguish four black dots on the dorsal (back) side of each segment of the abdomen and a light-colored, upside-down “Y” marking on the head capsule (Figure 2). Fall armyworms, similar to some other immatures of moth species, have four pairs of prolegs attached to the abdomen. Adult moths are more difficult to distinguish from other species. Each moth has a wingspan of approximately 1-1 ½ inches, the hind wings are white (same as cutworms) but the fore (front) wings have a noticeable white spot near the center of the wing (Figure 3).

Figure 1. Fall armyworm larva.Figure 1. Fall armyworm larva. M. BertoneFigure 2. Fall armyworm head capsule.Figure 2. Fall armyworm head capsule. L. J. Buss, UFFigure 3. White spot on wings.Figure 3. Fall armyworm markings. L. J. Buss, UF

Pest Status

Fall armyworms have a very wide host range but generally prefer plants in the grass (Poaceae) family, low-growing herbaceous growth and woody shrubs. Most grasses, including coastal bermudagrass, fescue, ryegrass, bluegrass, Johnsongrass, timothy, corn, sorghum, Sudangrass, and small grain crops, are subject to infestation.

Biology

Fall armyworms that attack turf in North Carolina likely overwintered as pupae in Florida. As the adults emerge from their pupal cases, they migrate northward throughout the spring and summer. Fall In mid-summer (July), female moths lay eggs in clusters on the surface of most kinds of vegetation (Figure 4). They will also lay eggs on flat surfaces of neighboring structures (posts, signs, buildings). On moth can lay as many as 1000 eggs which hatch within 2-10 days. As the eggs hatch, the larvae feed on the remains of the egg mass then drop to the soil surface to search for food. Unlike other caterpillar species, fall armyworms will feed day or night, but are usually most active early in the morning or late in the evening. In large populations, fall armyworms can consume all the foliar tissue available and crawl in “armies” to nearby crops or turf stands. After the larvae feed for 2-3 weeks, they dig into the soil and pupate. Within two weeks, a new population of moths emerges. Several generations occur each year in North Carolina and earlier infestations tend to occur following a mild winter.

Figure 4. Fall armyworm egg mass.Figure 4. Fall armyworm egg mass. J. Castner, UF

Damage

Although armyworms may be better known as agricultural crops pests, they can be a sporadic but serious pest of turfgrasses. Fall armyworm damage in turfgrass is very distinctive. Since armyworms cross the turf surface as a group, they create a noticeable line between damaged and undamaged turfgrass (picture of armyworm damage). Usually damaged areas will originate around a site where egg masses can be easily laid (signposts, buildings) and radiate outward. Although fall armyworms do not have many specific preferences, newly-installed sod is more attractive and more susceptible to damage.

Control

Biological Control

Often, natural enemies can keep fall armyworm populations in check. However, cold, wet springs can reduce the effectiveness of parasitic organisms and cannot effectively control large armyworm populations.

Chemical Control

Fall armyworms can be more difficult to control than other caterpillar pests (true armyworms, black cutworms). When possible, mow and lightly irrigate the turf prior to treating. Insecticides are generally ineffective against large larvae so be sure to note the size of the armyworms before making an application. Large larvae are likely to finish feeding and burrow into the soil to pupate so only treat if larvae are relatively small. Pyrethroids (particularly lambda-cyhalothrin) and carbamates (carbaryl), will provide somewhat effective control against smaller larvae. Chlorantraniliprole will also control turf-feeding caterpillars, if applied very early. For specific control information, consult your North Carolina Cooperative Extension center for recommendations.

Insecticide and Formulation

Amount per 1,000 sq ft

Precaution and Remarks

acephate* (Orthene, T, T&O) 0.5 to 1.2 oz Water in immediately after application.
chlorantraniliprole (Acelepryn) 0.046 to 0.092 fl oz
chlorpyrifos* (Dursban) 4 E, 2 E, 50WP, Pro See label For use on golf courses; check new label.
indoxacarb (Provaunt) SC 0.0625 to 0.25 fl oz Not labeled for use on sod farms.
pyrethroids* (Advanced Garden, Battle, Deltagard, Menace, Scimitar, Talstar, Tempo, Cyonara) See label
spinosad A + D (Conserve) SC 1.25 fl oz Rate varies with size and species

Written By

Photo of Terri Billeisen, N.C. Cooperative ExtensionDr. Terri BilleisenExtension Associate (919) 515-7464 tlhoctor@ncsu.eduEntomology & Plant Pathology - NC State University Photo of Rick Brandenburg, N.C. Cooperative ExtensionDr. Rick BrandenburgExtension Specialist (Peanuts & Turf) & Department Extension Leader (919) 515-8876 rick_brandenburg@ncsu.eduEntomology & Plant Pathology - NC State University
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This Extension factsheet can also be viewed at:
https://content.ces.ncsu.edu/fall-armyworm-in-turf