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Seed Treatments to Manage Maggots and Soilborne Diseases in Onion, 2026

Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program

Last Modified: October 1, 2025

Seed Treatments to Manage Maggots and Soilborne Diseases in Onion, 2026

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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NY Urban Farms Pest Management Fact Sheet Series

Cornell Cooperative Extension has partnered with dozens of urban farms across New York State to demonstrate and evaluate sustainable pest management strategies. Together with farmers, we found success using control methods that prevent or reduce crop losses through exclusion strategies, crop timing, host resistance, the introduction of beneficial organisms, and more. Regardless of management strategy used, common requirements for success include a knowledge of the pest and disease complex, preventative deployment and commitment to the process. The New York Urban Farms Sustainable Pest Management Fact Sheet Series includes case studies highlighting pest management techniques that New York urban farms have found valuable.

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