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Seedcorn Maggot in Soybeans

Seedcorn maggots are a slowly increasing below-ground threat to soybean production. Changes in agronomic practices in recent years, including reduced tillage, cover crops and fresh manure applications, have contributed to the increasing prevalence of this pest in many areas. These practices leave residue on the field, creating enticing conditions.

Seedcorn maggot pupae

Seedcorn maggots overwinter as pupae and emerge as flies in the early spring. They can sense the degrading organic matter in the soil and will fly into those fields to lay their eggs. Larvae hatch in 7-10 days and begin feeding on seeds and young seedlings.

Seedcorn maggots cause damage by attacking the seed and tunneling through the shoot. As a result, some plants wilt and others never even emerge, leaving large gaps in the soybean stand. Nibbling of cotyledons is another symptom of seedcorn maggots.

Seedcorn maggot on soybean

What make seedcorn maggots so threatening is you can’t always predict when they will appear. You can scout for some pests more easily, like wireworms and white grubs, as they overwinter as larvae, but seedcorn maggots overwinter as pupae in the soil, which are very small in size – similar to a grain of wheat. This makes them difficult to locate.

Even if you don’t have residue in your soybean field, they could be attracted by a neighboring field that does. Seedcorn maggots can fly far distances and devastate whole fields when conditions are conducive. Insecticide seed treatments are the only option to protect against this particular pest.

Management Tips
  • Scout for pupae of seedcorn maggots in the fall.
  • Fields with a history of persistent seedcorn maggot pressure should consider late and shallow planting and higher seeding rates.
  • Plant only once the soil has reached an appropriate soil temperature.
  • Avoid heavy manure applications in the 3-4 weeks before planting.
  • Kill or plough down green manure or cover crops at least 3-4 weeks ahead of planting.

Seedcorn maggot Cotyledon damage​​​​​​​

Protection from Below-Ground Feeding
Early-season protection against pests like seedcorn maggot is critical to give your soybeans a strong start. Golden Harvest® Preferred Seed Treatment, powered by Cruiser® seed applied insecticide, offers good protection from seedcorn maggots and other soilborne pests. Not all seed treatment packages contain insecticides, so always make sure to ask specifically that a seed applied insecticide is included in your next treatment. 

Visit with your local Golden Harvest Seed Advisor or agronomist with questions or for help evaluating insect pest damage.

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Syngenta hereby disclaims liability for third-party websites.

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