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Closely monitor sunflower fields for cutworm outbreak.

Agronomy Bulletin 78 ─ Managing Cutworms

Cutworms feast on previously damaged plants near the soil surface as well as a sunflower's cotyledons and subsequent early leaves.

Situation

Cutworms can devastate sunflower plant stands if left unchecked and untreated. Perhaps their biggest asset is grower underestimation of the damage that can occur. Before planting, consider best practices for protecting your crop.

Factors to Consider

  • Cutworm life cycle
  • Potential damage
  • Scouting and action threshold
  • Management options

Action Plan

  1. Know cutworms' life cycle. Cutworms lay eggs in the late summer rather than spring. Since eggs overwinter before emerging as larva in the warmer soils of spring, they are ready to attack as large, voracious pests by mid-May. Cutworms then feed on weeds and crop until mid-June before retreating back into the soil to pupate. They return as moths to lay several hundred eggs before dying off in the fall.
  2. Recognize the costly risks. Cutworms can completely destroy sunflower yield potential if the pest is left unchecked. Cutworms feast on previously damaged plants near the soil surface as well as a sunflower’s cotyledons and subsequent early leaves. Fields planted in populations lower than 15,000 plants per acre face a greater risk to cutworm outbreaks.
  3. Carefully inspect your fields. Since most cutworm damage occurs at night, rendering daytime detection difficult, growers need to be particularly watchful. Beginning at crop emergence, check sunflower fields twice per week through mid-June. Cutworms will first appear in areas where soils warm fastest, such as hilltops and lighter soils. Upon finding a clipped plant, dig down a few inches to find cutworm larva. If there is more than one larva per square foot or if there is a 25 percent stand reduction, take action.
  4. Defend your crop with the right insecticide. Farmers with a history of cutworms often spray in early spring to prevent outbreaks. Those producers should still check each week for an outbreak. More aggressive action should be taken between May and mid-June, when cutworms are more problematic (after June, the threat of cutworms is relatively remote). There are numerous labeled commercial insecticide options for controlling cutworms in sunflowers, including Lorsban®-4E insecticide. Because of cutworms’ evening activity, nighttime application of insecticide is most effective. Note that insecticide seed treatments are not labeled to control cutworms.

Summary

Cutworms can destroy entire fields. Scout your fields twice each week between crop emergence and mid-June. If cutworm damage reaches economic thresholds, insecticides will help you regain control. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Resources

Published on Wednesday, July 31, 2013