Unpredictable pests devastate stands.
Agronomy Bulletin 32 ─ Managing Black Cutworm
A high rate of black cutworm (BCW) moth catches, green fields and late planting dates are the perfect recipe for significant damage from black cutworm. Damage can range from very little to almost 100 percent stand loss. To give late-planted corn the best yield potential, make controlling this pest a high priority.
Factors to Consider
- Life cycle
- Scout for the pest. Timely detection of BCW infestations requires periodic inspection, at least once per week, starting with the first emergence of the corn stand to the V6 leaf stage. Look for wilted or cut plants, always being aware that cutworms sometimes cut off the plant below the soil surface.
- Recognize the pest. Larvae of the BCW vary in color from light gray to black. They have four dark tubercles on top of each abdominal segment, and mature larvae can be up to 1½ inches long. Total feeding time for the larvae ranges from 20 to 30 days, and those in the fourth to fifth instar stage cause the most damage.
- Understand the life cycle. BCW adults do not overwinter in Northern states but rather migrate from the South in April and May. Female moths will lay eggs in fencerows, pastures, plant debris and fields with weedy vegetation — especially those with winter annuals. Larvae go through seven stages and are most damaging during the third and fourth stages, when they are ½ to ¾ inch long.
- Know when treatment is necessary. Select a rescue treatment if 3 percent or more of the plants have been damaged, corn plants are in the V2 to V6 stage of development and larvae are still 1 inch or less. Reference Table 1 to predict the development of BCW larvae based on accumulating degree-days (warmer than 50 F).
When every extra bushel of yield pays, don’t ignore the agronomic factors that can affect a crop. Although small, black cutworms can cause big losses. To prevent yield loss, select hybrids with in-plant insect protection from SmartStax® or Herculex® Insect Protection and work with a Mycogen Seeds representative to pick the hybrid that will perform the best in your area. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.
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