True ArmywormArmyworms may feed on seedling corn, in whorls, and occasionally on developing kernels. Because they may appear in large numbers, quick control is important. Feeding from smaller armyworm larvae can result in “window-paning” of the upper side of leaves, while large larvae can chew holes in leaves.

Fall armyworms are multicolored, striped caterpillars with a characteristic inverted “Y” on the head and four pairs of abdominal prolegs.

Mature True Armyworm larvae are smooth, almost without any hairs, greenish-brown to reddish-brown, with a dark stripe along each side. A broad dorsal stripe runs down the length of the back. This species differs from the fall armyworm by having a dark lateral band on the outer portion of each proleg.

Sampling: During the whorl stage, look on the undersides of leaves for fall armyworm egg masses. Fall armyworms lay their eggs in clusters of 50 to several hundred on corn leaves and other vegetation.

Pheromone (sex-attractant) traps are also used to monitor various insect flights, and can complement an effective scouting program. Traps can be used in each county or on individual farms to provide producers with advance warnings of insect infestations.

Seedling plants. Treat when 50 percent of the plants have one or more larvae per plant.

Whorl stage or larger plants. Controls should be initiated when 75 percent of whorls have larvae present. Control of larvae in ears is not economically practical in field corn.

Management options

Insecticide (Trade Names) for FALL ARMYWORMLb Active Ingredient per AcreAmount Formulation per AcrePerformance Rating
bifenthrin (Brigade 2E, Discipline 2E, Fanfare 2E)0.063 - 0.104 - 6.4 oz6
carbaryl (Sevin XLR Plus 4)1 - 232 - 64 oz4
chlorpyrifos (Lorsban 4E, Nufos 4E)*0.75 - 124 - 32 oz4
chlorpyrifos (Lorsban Advanced 3.755)*0.70 - 0.9424 - 32 oz4
chlorantraniliprole (Prevathon 0.43 SC)0.05 - 0.0714 - 20 oz9
chlorantraniliprole, λ-cyhalothrin (Besiege)see label6 - 10 oz9
methomyl (Lannate LV 2.4)*0.225 - 0.312 - 16 oz7
methoxyfenozide (Intrepid 2F)0.6 - 0.1254 - 8 oz7
permethrin (Pounce 3.2E)0.1 - 0.24 - 8 oz5
spinetoram (Radiant SC 1)0.02 - 0.053 - 6 oz8?
spinosad (Blackhawk 36% WDG)0.04 - 0.071.7 - 3.3 oz7
β-cyfluthrin (Baythroid XL 1)0.022.8 oz6
γ-cyhalothrin (Declare 1.25)0.01 - 0.0151.02 - 1.54 oz6
λ-cyhalothrin (Karate 2.08, Warrior II)0.02 - 0.031.28 - 1.92 oz6
Z-cypermethrin (Mustang Max 0.8E)0.02 - 0.0253.2 - 4 oz6
  • Production of an early crop and preservation of beneficial insects will reduce the risk of armyworm outbreaks.
  • Several of the new Bt corn technologies  are effective at controlling fall armyworms in corn ears.