Texas A&M University is cautioning the state's producers that conditions are right for an armyworm population explosion this fall. Chris Sansone, extension entomologist at San Angelo, says fall rains can trigger armyworm onslaughts that can destroy pastures and small grain fields almost overnight. "Conditions are ideal for a real invasion of these pests in coming weeks," he says. "This insect can build up large numbers seemingly overnight, causing crops and lawns to disappear before your eyes. The adults lay thousands of eggs, and by the time the larvae are big enough to see, the damage is done."
Sansone says the larvae chew the green layer from leaves and leave a clearing or "windowpane" effect. The first three larval stages do little damage and are easy to control. The final two stages can eat 85% of the total foliage consumed by the larvae. "That's the reason it's so important to find the infestations before the caterpillars get too large," Sansone states. "Small larvae are easier to control and most of the damage can be prevented if the infestation is caught early. Individual fields need to be scouted carefully, because the moths don't lay eggs consistently across an area." Often, a pasture or small grain field will be infested while the field across the road is armyworm-free. Fall armyworms are worse in the autumn, when adult moths are carried into an area with cold fronts that trigger rain. The insects are a threat until the first hard freeze.