2026 Onion Fungicide Cheat Sheet for Control of Leaf Diseases
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program

The 2026 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.

Upcoming Events
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Ontario
July 28, 2026
Canandaigua, 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 available: 2.0 in categories 10, 1a, 23 and 24.
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Seneca
July 29, 2026
Romulus, 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 available: 2.0 in categories 10, 1a, 23 and 24.
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Yates
July 31, 2026
Himrod, 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 available: 2.0 in categories 10, 1a, 23 and 24.