Soybeans: Seedcorn Maggot

Excerpt from Agronomy Guide for Field Crops (Chapter 4)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Description
2. Life History
3. Damage
4. Scouting Techniques
5. Action Threshold
6. Management Strategies
7. Updates on Soybeans: Seedcorn Maggot
8. Related links...

Description

The seedcorn maggot is a small, yellowish-white, headless, legless larva. The body tapers to the front with two small mouth hooks protracting. The maggots burrow into germinating seeds and the below-ground parts of emerging seedlings, producing weak seedlings. The adults resemble a small housefly that is slender, light grey and approximately 5 mm in length.

Plate 53. Seedcorn maggots are small, headless, legless larvae that burrow into germinating seeds and weaken the seedling.

Life History

Seedcorn maggot adults (flies) will mate, and the female will search for an egg-laying site from April until the middle of June. The females are attracted to moist soils that give off an odour of decaying organic matter such as crop residues, areas where manure has been applied or freshly tilled soil. Weeds are also attractive to females. The adults lay their eggs in the soil. The larvae then develop in the soil and organic residue, feeding on germinating seeds.

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Damage

Seedcorn maggot is usually a problem during cool, wet springs when germination is delayed. The maggots feed on the swollen, ungerminated seed. They can be found in the cotyledon, embryo and hypocotyl. Slow emergence and or reduced stand establishment can occur. Seedlings that escape and germinate often die or lag behind.

Scouting Technique

Unlike wireworm, seedcorn maggot damage is usually found over a generalized, large portion of the field. Nothing can be done to rescue a damaged field except replanting if necessary. High-risk factors include freshly tilled soil with heavy crop residue, recently applied manure, recently tilled green manure and deep planting, along with cool, backwards emergence conditions in the forecast.

Action Threshold

No threshold is available at this time.

Management Strategies

Consider insecticide seed treatments in early-planted fields where large amounts of manure or residue have been recently incorporated or primary tillage has recently occurred. Use good-quality seed that will emerge quickly. See OMAFRA Publication 812, Field Crop Protection Guide, for recommended registered products. There are no rescue treatments available. (Order OMAFRA Publication 812)

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Updates on Soybeans: Seedcorn Maggot

• Field Crop Protection Guide - Publication 812
  • Soybeans: Seedcorn Maggot

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Related links...

• Insects
• Soybeans

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