Armyworms primarily are abundant during August through early November; however, we have already received early reports around the area of small outbreaks, some coming from right here in Panola County. In a matter of days, armyworms can occur in very large numbers, consuming a field overnight, moving in large masses or “armies” to adjacent fields in search of more food.
Not being able to overwinter in the area due to our cold temperatures, the eggs they hatch from are deposited here by the moths that fly north from South Texas, re-infesting the area each year, with outbreaks often occurring in late summer and fall following periods of rain, which create favorable conditions — just as the weather we just had. Armyworm moths lay their eggs, which can be as many as 2,000 in masses of up to 50 eggs on grass leaves, hatching in 2-3 days of being laid, making it hard to find them at this stage.
Fall armyworms are green, brown or black, with a distinct white line between the eyes forming an inverted “Y” pattern on the face. There are four black spots aligned in a square on top, near the back end of the caterpillar. Armyworms are very small at first, causing little plant damage; as a result, infestations often go unnoticed. The caterpillars feed for 2-3 weeks reaching a size of 1 to 1.5 inches at maturity, before pupating. It is at the end of their larvae stage where they consume roughly 80 percent of their total food intake. Fortunately, this stage in the life cycle last only a few days. Given their large appetite, number, and mobility, armyworms can damage entire fields in a few days or even hours.
Once the worms complete feeding they tunnel back into the ground, entering an inactive non-feeding stage where they transform into pupae for 7-10 days at which time they re-emerge as the armyworm moth repeating the cycle again. In all, development from egg to adult requires about four weeks during the warmer summer temperatures and is longer during cooler fall weather, allowing for several generations a year.
The key to being able to manage armyworm outbreaks is early detection before they can cause economic damages. Armyworms primarily feed during the night or on cloudy cooler days. For most days, look for the larvae under loose soil and fallen leaves on the ground beneath the grass canopy. Presence of chewed leaves can indicate their presence. Once the larvae reach a size greater than 3/4 inch, the quantity of leaves they eat increases dramatically, which is one reason infestations can go unnoticed.