Many producers vividly remember their encounters with fall army worms. The discovery of large, later stage army worms in one’s pasture quickly leads to tremendous destruction of valuable forage. Producers generally see the damage of these pests in late July/August through early fall.
Mature fall army worm moths lay eggs that hatch after just 2-4 days. Upon hatching, young army worms begin to feed and grow. Army worm growth occurs in stages, with the worms’ capacity for destruction increasing with each growth stage. Army worms reach full size 2-3 weeks after hatching, and will then burrow into the soil for 10-14 days. Afterward, they emerge as mature army worm moths and continue the life cycle.
A key to managing fall army worms is the understanding of their life cycle and growth phases. Shortly after hatching, small worms are far less destructive than their more mature counterparts. Figure 1 demonstrates the amount of damage observed from worms at each growth stage. Notice that the vast majority of damage occurs during the last growth phase (which occurs 2 weeks after their hatching). Scouting for worms before you notice their destruction allows for one to spray and kill the worms while they are small and in earlier, less destructive growth phases. This reduces their negative impacts on one’s pastures and allows for better control of future infestations since the lifecycle is interrupted.
Use a sweep net to scan your pastures for worms. Follow the links to view a video or article on proper sweep net usage. Treatment for fall army worms is effective if worms are found early on. If infestation is discovered too late, major destruction may be unavoidable. This is why it is essential to scout for worms BEFORE you notice their impact on your forages. Once discovered, worms can be killed by spraying. Click here for an article that contains suggestions for fall army worm control.
Also, remember to help your fellow producers know if army worms are in your area by reporting occurrences of fall army worms. Click here to view the updated map of army worm infestation in Alabama, and let us know if you have fall army worms.
More information about fall army worms is available at the Alabama Forages Pest Management website in the Fall Armyworm section.
If you have questions regarding managing fall armyworms, contact myself or other members of the ACES Animal Science and Forages Team.
Sarah Dickinson, M.S.
Regional Extension Agent I
Animal Science & Forages
Alabama Cooperative Extension System
Serving Chambers, Clay, Cleburne, Coosa, Lee, Randolph, Shelby, Talladega, and Tallapoosa Counties