Seed Treatments to Manage Maggots and Soilborne Diseases in Onion, 2026
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program

Because onions are attacked by the onion maggot (Delia antiqua) and seedcorn maggot (D. platura), determining which insecticide seed treatments to use for managing both is important. Our recent research has shown that seedcorn maggot may kill onion seedlings before and shortly after emergence, while onion maggot is the dominant species that kills onions after emergence (80-90% of infested plants), and seedcorn maggot is less prevalent (10-20% of plants).
The "Cheat Sheet" for Seed Treatment and In-Furrow Treatments for Managing Maggots and Soilborne Diseases in Direct-Seeded Onion in New York, 2026 provides an update on insecticide options for managing both maggot species using seed treatments based on results from multiple Cornell field trials in Oswego County from 2023 to 2025.
Cheat Sheet for Seed Treatments to Manage Maggots and Soilborne Diseases in Onion, 2026 (pdf; 259KB)

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2026 Muck Onion Growers Twilight Meeting in Oswego
June 18, 2026
Oswego, NY
Open to all Onion Enthusiasts, the Muck Onion Growers Twilight Meeting will include an onion disease research update from 2025, new fungicide recommendations for 2026, an onion maggot seed treatment update, herbicide demonstration tour, and more. This educational event is immediately followed by a catered dinner; both are FREE thanks to generous sponsors!
2.25 DEC recertification credits available in categories 1a, 10 and 23. CCA credits will be offered too.