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Beginner

Scientific Name
Delia platura

Identification

• Small (<5 mm or ¼ in.) translucent white maggots
  
• Legless and oblong-shaped with a pointed anterior
  
• Adult is a small (5 mm, ¼ in.) grey-black fly
  
• Infestations often result in un-emerged seedlings, wilted transplants and poor stand establishment

Often Confused With
Wireworm
Damping-off and root rots

Period of Activity
Maggots are usually a problem during cool, wet springs when germination is delayed. Adult flies lay their eggs from April until the middle of June.

Scouting Notes
While walking fields, look for wilted plants and/or gaps in the plant stand where the seedlings have failed to emerge. Dig around the seed trench to look for the cause of the damage. Seedcorn maggots are often found in the seed.  They will also tunnel up the stem of newly emerged seedlings and transplants.  Record the percentage of the field impacted by root insect damage.

Thresholds
None established.

Advanced

Scientific Name
Delia platura

Identification
The translucent white maggots are small (< 5 mm or ¼ in.), legless and oblong-shaped with a pointed anterior. The adult seedcorn maggot is a small (5 mm, ¼ in.) grey-black fly.

Seedcorn maggot feeding causes poor or uneven emergence. Un-emerged seeds often have small maggots feeding on the embryo. Maggots may also attack young seedlings, shortly after emergence. They burrow into the stem at ground level, causing the affected plants to wilt and die rapidly.

Often Confused With
Wireworm
Damping-off and root rots

Biology
Seedcorn maggots overwinter as pupae in the soil.  The adults emerge in early spring. Females often deposit their eggs on fresh manure applications or decomposing crop residue. Larvae hatch in 7- 10 days and remain in the field for 1- 3 weeks feeding on residue, seeds and young seedlings.  Larvae may be active at soil temperatures as low as 10°C (50°F). There are 3- 6 generations per year. Once the plants grow past the seedling stage, they are no longer susceptible to seedcorn maggot injury.

Period of Activity
Seedcorn maggots are commonly found during cool, wet springs when germination is delayed and early crop growth is slow.

Scouting Notes
While walking fields, look for wilted plants and/or gaps in the plant stand where the seedlings have failed to emerge. Dig around the seed trench to look for the cause of the damage. Seedcorn maggots are often found in the seed. They will also tunnel up the stem of newly emerged seedlings and transplants. Record the percentage of the field impacted by root insect damage.

Thresholds
None established.

Management Notes

• Plant into warm soils. 
  
• Cucurbits will not germinate until the soil temperature reaches a minimum of 16°C (60°F). 
  
• 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.