Black cutworm adults were caught in pheromone traps across Iowa in April and early May. From these collections, we can project the likely first cutting dates of seedling corn across Iowa. As reported  in last week's ICM Newsletter, black cutworms could be large enough to cut corn now in the southern three tiers of counties. In addition, cutting could occur by May 8 in west central Iowa and by May 11 in central and east central Iowa. Farmers in the northernmost three tiers of counties could have larvae large enough to cut corn starting May 15.
This year, there have been several successive moth flights, so once scouting starts there could be feeding activity by caterpillars of several sizes over an extended period of time. Before cutting occurs, small cutworms often eat pin-sized holes in the leaves. Some producers may decide to mix an insecticide with a herbicide application when they see this injury. Before the insecticide is included in the application, confirm that black cutworms are the insects in the field that are responsible for the leaf-feeding injury. There are no economic thresholds for pin-hole feeding, only cutting, so a treatment based only on these small holes may not be the most judicious and economical decision. Use insecticides wisely.
This article originally appeared on pages 74-75 of the IC-486 (9) -- May 14, 2001 issue.