We have had substantial black cutworm moth (Figure 1.) catches in our pheromone traps. Black cutworm moths typically lay their eggs on winter annual weeds growing in un-tilled fields. When the eggs hatch, the larvae will begin feeding on the weeds. Then, when you kill the weeds with either tillage or a burndown herbicide, the larvae are left there with nothing to eat. If you wait a couple of weeks to plant, they will probably starve to death. If you plant sooner than that, they will just be really hungry and will readily attack a variety of crops. The pyrethroid insecticides provide good, economical control.
Figure 1. Black cutworm larva (Photo by John Obermeyer)