2025 Onion Fungicide Cheat Sheet for Control of Leaf Diseases
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program

The 2025 Cornell Onion (Dry Bulb) Fungicide "Cheat Sheet" for Control of Leaf Diseases in New York provides relative performance rankings for Botrytis leaf blight and Stemphylium leaf blight of the main fungicide options that may be used in New York to control these diseases, based on recent on-farm fungicide trial results, which reflect reduced efficacy of SLB due to development of fungicide resistance. It includes active ingredients, FRAC codes, rating for risk of fungicide resistance, activity on downy mildew, maximum use rates, and photos.
2025 Onion Fungicide Cheat Sheet for Control of Leaf Diseases in New York (pdf; 352KB)

Upcoming Events
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.