Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
4/25/00
Contacts:
Marlin Rice, Department of Entomology, (515) 294-1101
Rich Pope, Department of Entomology, (515) 294-1101
Julie Todd, Extension Communication Systems, (515)
294-2405
Avoid Preplanting-Time Insecticide Treatments For Black Cutworm
AMES, Iowa -- Black cutworm pheromone (insect attractant) traps that are monitored by Iowa State University Extension cooperators across Iowa captured large numbers of moths the third week in April. These trap captures resulted in some insecticide dealerships and companies promoting their insecticides as preplant treatments to prevent black cutworm injury to corn. However, preplanting-time insecticide treatments for black cutworms are not a good idea.
Rich Pope, ISU Extension program specialist coordinates a network of traps in more than 75 Iowa counties to monitor when black cutworms arrive and potentially lay eggs. "Trap capture information is valuable because it allows scientists to predict when crop damage may occur. Farmers can scout and treat only fields that are being damaged," Pope said.
Marlin Rice, ISU professor of entomology, said, "Preplant treatment is not a good integrated pest management practice. The trap capture data do not indicate where the females lay their eggs, how many eggs they lay, what the cutting potential is, or even whether moths stay within the area where they were trapped. Moths may depart the next night and continue their migration northward to Minnesota or eastward to Illinois. Trap captures alone do not mean the females have laid eggs in a field."
Rice suggests an integrated pest management strategy for control of black cutworms. "Delaying treatment until a black cutworm problem develops in the field makes economic sense. Early treatments add expense, but with no benefit if no cutworms show up," Rice said.
Companies may guarantee preemergence-applied insecticides for black cutworm control. Insecticide performance guarantees should not lull farmers into a false sense of security. "Just because the field was sprayed early in the season does not preclude the possibility of crop injury by insects later in the season. To use the guarantee, a field must be scouted to confirm that the field is either being protected (or not) against stand loss," Rice said.
In addition, the scouting-based treatment may do double duty in controlling corn flea beetles, a secondary benefit missing from the early treatment strategy. When scouting, look for early signs of injury, positively identify the insect and determine whether the economic threshold has been reached. That way, an insecticide treatment can pay off.
If you have questions about black cutworm management, contact your ISU Extension county office.
ml: isufarm
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