Armyworms can be serious pests of wheat when populations reach large numbers. Armyworms get their name from their migrating habit, as they sometimes start at one portion of the field and migrate to other areas of other fields, eating foliage as they go.
True armyworm larvae are smooth, almost without any hairs, and 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. Damaging infestations of true armyworm normally occur in the spring. Besides feeding on foliage, larvae will sometimes cut the heads of maturing wheat plants.
Fall armyworms are normally a pest of early planted seedling wheat during the fall. These insects can completely defoliate a wheat field when populations are very large. Fall armyworm larvae differ from true armyworms by having a prominent inverted Y on the front of the head and no dark bands on the outer portion of the prolegs.
Management options
| Insecticide (Trade Names) for ARMYWORMS (True and Fall) | Lb Active Ingredient per Acre | Amount Formulation per Acre | Performance Rating |
|---|---|---|---|
| chlorantraniliprole (Vantacor 5 SC) | 0.047 - 0.067 | 1.2 - 1.71 oz | 9 |
| chlorantraniliprole, λ-cyhalothrin (Besiege) | See label | 6 - 10 oz | 9 |
| methomyl (Lannate LV 2.4) | 0.225 - 0.45 | 12 - 24 oz | 7 |
| spinetoram (Radiant SC 1) | 0.023 - 0.047 | 3 - 6 oz | 9? |
| spinosad (Blackhawk 36% WDG) | 0.038 - 0.074 | 1.7 - 3.3 oz | 8 |
| β-cyfluthrin (Baythroid XL 1) | 0.014 - 0.019 | 1.8 - 2.4 oz | 8 |
| γ-cyhalothrin (Declare 1.25) | 0.01 - 0.015 | 1.02 - 1.54 oz | 8 |
| λ-cyhalothrin (Warrior II 2.08) | 0.02 - 0.03 | 1.28 - 1.92 oz | 8 |
| Z-cypermethrin (Mustang Maxx 0.8) | 0.02 - 0.025 | 3.2 - 4 oz | 8 |
- Avoid planting before the Hessian fly free date (Oct. 15) as infestations of fall armyworm almost always occur in early planted wheat, especially for wheat planted in September.