The fall armyworm (FAW) is a common pest of bermudagrass, corn, sorghum, and small grains. We commonly see FAW after late summer and fall rains on good, lush forage. However, we have already had a pretty good flush of FAW’s in the county, meaning there is certainly potential for a larger outbreak. In the future, once we start having pasture mealybug outbreaks, we will have to be especially careful about which products we use to control FAW. This is because beneficials provide very good control on the mealybug but many of the products we use to control FAW will also kill off those beneficials. However, at this time we have not found an active case of mealybugs in the county (fingers crossed).
The larvae of the fall armyworm are green, brown, or black with white to yellowish lines running from head to tail. There will be a white line between the eyes that forms a “Y” pattern on the face. At first, the fall armyworm caterpillar or larvae are very small about 1/8”; at this stage they cause very little damage and usually go unnoticed. The larva will feed for 2 to 3 weeks growing to 1 to 1.5”. Once the armyworm reaches ¾” in length, the quantity of forage they eat increases dramatically. During the final 2-3 days of feeding, armyworms consume 80% of the total forage during their entire development. Once the armyworm completes feeding it will tunnel into the soil and enter the pupal stage. The moth emerges from the pupa in about 10 days and repeats the lifecycle.
Scouting is the key to controlling damage associated with the fall armyworm. It is best to check fields late in the evening or early in the morning- this is when they will be feeding in the upper canopy. Damage from the small larvae will leave a clearing or windowpane effect on the leaf. As the larvae grow, they will begin eating on the edges of the leaves.
The following is a list of insecticides for fall armyworm control provided by Texas A&M AgriLife Extension Entomologists.
Insecticides Labeled for Armyworm Control in Pastures and Hayfields Always read and follow all label instructions on pesticide use and restrictions. Information below is provided for educational purposes only. Read current label before use and check with your local applicator and pesticide provider for the most economical product for your operation.
Karate Z. 13.1% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.
Lambda- Cy. 11.4% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.
Mustang Max. 9.6% zeta-cypermethrin. Fall armyworm and g r a s s h o p p e r s . Applications may be made for 0 days for forage and hay, 7 days for straw and seed screenings. Restricted use insecticide.
Tombstone Helios. 25% cyfluthrin. Fall armyworm and grasshoppers. Pasture, rangeland, grass grown for hay and seed. Zero days to grazing or harvesting hay. Restricted use insecticide.
Warrior II. 22.8% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.
Baythroid XL. 12.07% cyfluthrin. Fall armyworm and grasshoppers. Pasture, rangeland, grass grown for hay and seed. Zero days to grazing or harvesting hay. Restricted use insecticide.
Dimilin 2L. 22% diflubenzuron. Fall armyworm and immature grasshoppers. Dimilin must be applied before armyworm larvae reach ½ inch or larger. Provides residual control for up to 2-3 weeks, as long as forage is not removed from the field. Label does not list a restriction on grazing.
Vantacor 5% chlorantraniliprole. Fall armyworm and grasshoppers. Vantacor has a 0-day waiting period for harvest or grazing and is not a restricted use insecticide.
Besiege 9.26% chlorantraniliprole and 4.63% lambda cyhalothrin.
Fall armyworm and grasshoppers. Pasture and rangeland grass may be used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.
Sevin 4F, Sevin XLR, Sevin 80S, Generic Carbaryl. Fall armyworm and grasshoppers. When applied to pastures, there is a 14-day waiting period before grazing or harvesting.
Malathion 57% and Malathion ULV. Fall armyworm and grasshoppers. Zero days to harvest or graze.
Intrepid 2F. Fall armyworm ( not grasshoppers). Begin applications when first signs of armyworm feedings appear. Use higher rates for heavier infestations. Do not harvest hay within 7 days of application. No preharvest interval for forage. 0 days to graze.
Tracer Treat when armyworm eggs hatch or when larvae are small. Use higher rates for larger larvae. Do not graze until spray is dry. Do not harvest hay or fodder for 3 days after treatment. Do not allow cattle to graze until spray has dried.