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)

Upcoming Events
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Chautauqua
July 14, 2026
Panama, NY
A field walk will demonstrate pest management in fresh market vegetables in both field and greenhouse (high tunnel) vegetables, primarily for those growing for wholesale auction. CCE Cornell Vegetable Program Specialist Judson Reid will identify weeds, insects and diseases in vegetables and will go over management options such as inter-row cover crops, grafting, and where appropriate, spray options.
DEC recertification credits will be offered.
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Allegany
July 15, 2026
Fillmore, NY
A field walk will demonstrate pest management in fresh market vegetables in both field and greenhouse (high tunnel) vegetables, primarily for those growing for wholesale auction. CCE Cornell Vegetable Program Specialist Judson Reid will identify weeds, insects and diseases in vegetables and will go over management options such as inter-row cover crops, grafting, and where appropriate, spray options.
DEC recertification credits will be offered.
Pest Management for Small-Scale Growers
July 23, 2026
Rochester, NY
Join us for a hands-on field day exploring integrated pest management tools for small-scale growing spaces and the opportunity to build community with local growers! Learn the best practices for using row covers, biocontrols, trapping, and more.