Armyworm, Bertha biology & life cycle
The Bertha armyworm overwinters as a pupae and adults emerge from mid-June until August. Females oviposit on the underside of the leaves and larva hatch and disperse within one week. The larva are not highly mobile. As such, they will only migrate from a field when the food supply is short or the crop is over-ripe. In September the fully grown larvae enter the soil to pupate. There is one generation per year.