Onions
Onions are one of the most important vegetable crops in New York State with annual sales of approximately $52 million. New York accounts for 97% of the onion production in the North Eastern United States and ranks sixth in the nation. Approximately 12,000 acres of yellow pungent cooking onions are grown from direct seed, predominantly on organically rich muck soils. This crop is stored and marketed until April. Sweet and red varieties are also grown, mostly from transplants. Hundreds of small-scale diversified farms grow onions intensively on plastic beds on less than an acre. These onions can grow very large and be lucrative in the market place where they are sold through produce auctions, farmer's markets, roadside stands and CSAs.Continued intensive production of onions in New York has led to an array of perennial pest challenges, as well as the introduction of new pests, so that management of the onion complex in New York requires a very strategic research-based approach. Cornell Cooperative Educators and Cornell faculty work together to conduct research on many aspects of onion production in the state. Below you will find educational information and results of our research trials.
Relevant Events
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Ontario Produce Auction
July 15, 2025
Stanley, NY
Orleans Summer Vegetable Meeting, 2025
July 16, 2025
Waterport, NY
Lake Erie Region Summer Meeting
July 24, 2025
Brant, NY
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Seneca Produce Auction
July 30, 2025
Romulus, NY
Niagara Region Summer Meeting, 2025
August 7, 2025
Ransomville, NY
2025 Onion Fungicide Cheat Sheet for Control of Leaf Diseases
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
The 2025 Onion Fungicide Cheat Sheet for Control of Leaf Diseases in New York includes active ingredients, FRAC codes, rating for risk of fungicide resistance, activity on downy mildew, and maximum use rates.
Fungicide Sensitivity of SLB Isolates in Elba Onion Fungicide Trial, 2023
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
This table accompanies a research discussion and 2024 SLB recommendations article written by Christy Hoepting, CCE Cornell Vegetable Program, and Frank Hay, Cornell AgriTech appearing in VegEdge newsletter in July 2024.
Know the Difference: Botrytis Leaf Blight Halo Lesions vs BLB Necrotic Spots
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Through recent on-farm fungicide trials, we've determined that not all Botrytis leaf blight (BLB) lesions are controlled equally. There are two kinds of BLB lesions: BLB halo lesions and BLB necrotic spots and your best fungicide options for control of Botrytis leaf blight depends on what kind of spot you got!
Scouting Onions for Botrytis Leaf Blight Halo Lesions
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Botrytis Leaf Blight (BLB) halo lesions are the tiny pin-prick to pin-head sized yellow necrotic spots surrounded by silvery halos. The silvery halo is often blotchy in shape. Sometimes the necrotic spot is barely visible, which can make identification of such versions of these lesions tricky to identify. Here we show examples of BLB halo lesions and compare those to herbicide injury and various nicks.
A New Pest for the New Year in Western NY: Allium Leafminer is Here to Stay
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
In the fall of 2023, Allium leafminer (ALM) decimated leek crops in Orleans, Genesee, and Niagara Counties in New York. After its first detection in North America near Lancaster, PA in 2015, this invasive insect pest originating from Europe quickly established itself in southeastern New York, New Jersey, western Massachusetts, Delaware and Connecticut. It was only a matter of time that it would become established throughout New York. We are now assuming that ALM will occur throughout the 14-county Cornell Vegetable Program region in 2024. And, unfortunately, it is here to stay. Here is what Allium growers need to know.
Video: How to Identify Foliar Symptoms of Bacterial Disease in Onion
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
In this video, see the different forms of foliar symptoms of bacterial diseases of onion and how to distinguish bacterial diseases from other non-bacterial lookalikes.
Scouting Tips for Onion Thrips in Onions
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
To find the first thrips of the season, look deep into the leaf axils. Inspect 20 to 30 plants and count the total number of onion thrips (OT) per plant and divide by the average number of leaves per plant to get the number of OT per leaf. Thrips feeding causes silvery streaking along the leaves.
Insecticide Programs to Consider for Onion Thrips Control in Onion in 2023
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Guidelines for using insecticides to manage onion thrips in onion fields in the Great Lakes region continue to evolve as we gain more experience using them under various situations. The following guidelines provide multiple scenarios for managing onion thrips over the season in New York. The major factors used to create these guidelines are efficacy of products under varying levels of thrips pressure and the desire to follow insecticide resistance management principles.
2023 Guidelines for Onion Thrips Management for Onion
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
New York has a variety of registered insecticide products that can successfully control onion thrips in onion. This flowchart provides several different insecticide sequence options for controlling onion thrips in 2023.
Seed Treatments and In-Furrow Drenches in Muck-Grown Direct-Seeded Onion, 2022
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Between seed treatments and in-furrow drenches, there are many options for control of onion smut, damping off, and maggots in direct-seeded onions. This cheat sheet breaks down the active ingredients and their activity on the target pests.
2022 Cornell Onion Fungicide Cheat Sheets for Control of Leaf Diseases
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
These cheat sheets provide 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.
Video: How to Diagnose Onion Bacterial Bulb Rot
Bulb rot caused by bacterial pathogens can be confused with bulb rots caused by fungal pathogens as well as physiological disorders. It is important to accurately diagnose the cause of bulb rot/internal disorder in order to determine future effective preventative management strategies. In this simple 4 minute video, accurate identification of bulb rot caused by bacterial pathogens is distinguished from look-alikes caused by fungal pathogens Botrytis neck rot, Fusarium basal rot, black mold and blue mold and physiological disorders dry scale and translucent scale. Available in both English and Spanish.
Be on the Lookout for Southern Blight
Ethan Grundberg, Vegetable Specialist
Eastern New York Commercial Horticulture
Southern Blight (Sclerotium rolfsii) was found on golden storage beets this winter in Dutchess County. The fungal pathogen is fairly new to New York and poses a threat to a wide range of vegetable crops. Early detection and proper diagnosis are key to managing this disease.
Cold Storage Chart and Reference Guide to Commercial Vegetable Storage
Robert Hadad, Extension Vegetable Specialist
Cornell Vegetable Program
Commercial vegetable growers will find a Cold Storage Chart by crop type with temperature and relative humidity recommendations. The maximum number of weeks that the crop can be held under ideal conditions is provided as well.
Adapted from the USDA Bulletin #66, The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stock, growers will find information on quality, grading, sizes, and packaging, chilling and storage, and post-harvest pathology of vegetables.
Crop Cooling and Storage
Robert Hadad, Extension Vegetable Specialist
Cornell Vegetable Program
On-Farm Cold Storage of Fall-Harvested Fruit and Vegetable Crops is an in-depth look at the planning and designing cooling for late season and winter storage but it also is useful for general cooling as well. This was written by Scott Sanford, Distinguished Outreach Specialist, UW-Extension, and John Hendrickson, Outreach Program Manager, Center for Integrated Agricultural Systems, University of Wisconsin-Madison.
Fall Chemical Burn Down of Perennial Sow Thistle in Onions, 2013 Trial Results
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Perennial sow thistle has increased in economic importance and has become a serious weed problem for muck onion growers in the Western region on New York. In this project, we investigated fall chemical burn down strategies to manage this weed, as well as the use of a synthetic auxin growth regulator type herbicide, trade name Stinger to manage this weed in-season within an onion crop. Crop tolerance to Stinger was also studied.
Following is the first of three reports from 2013 Trials: Report No. 1. Simulated Fall Chemical Burn Down of Perennial Sow Thistle
In-Season Management of Perennial Sow Thistle in Onions, 2013 Trial Results
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Perennial sow thistle has increased in economic importance and has become a serious weed problem for muck onion growers in the Western region on New York. In this project, we investigated fall chemical burn down strategies to manage this weed, as well as the use of a synthetic auxin growth regulator type herbicide, trade name Stinger to manage this weed in-season within an onion crop. Crop tolerance to Stinger was also studied.
Following is the FINAL report and the first of 3 complimentary power point presentation files.
In-Season Management of Perennial Sow Thistle, 2013 Results (Part II)
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Perennial sow thistle has increased in economic importance and has become a serious weed problem for muck onion growers in the Western region on New York. In this project, we investigated fall chemical burn down strategies to manage this weed, as well as the use of a synthetic auxin growth regulator type herbicide, trade name Stinger to manage this weed in-season within an onion crop. Crop tolerance to Stinger was also studied.
Following are the second and third parts of the complimentary power point presentation.
Onion Crop Tolerance to Stinger (a.i. clopyralid)
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Perennial sow thistle has increased in economic importance and has become a serious weed problem for muck onion growers in the Western region on New York. In this project, we investigated fall chemical burn down strategies to manage this weed, as well as the use of a synthetic auxin growth regulator type herbicide, trade name Stinger to manage this weed in-season within an onion crop. Crop tolerance to Stinger was also studied.
Following is the final report:
Report No. 3: Onion Crop Tolerance to Stinger (a.i. clopyralid)
Responding to Hailstorms
Crystal Stewart-Courtens, Extension Vegetable Specialist
Eastern New York Commercial Horticulture
While no one wants to think about the possibility of hail hitting their beautiful crops just as they start to respond to the heat and take off, the likelihood that we will see more hail seems pretty high. So let's talk about it.
Exploring the Relationship Between Nitrogen, Plant Spacing and Bacterial Disease
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
It is important to emphasize that "exploring" is in the present tense. In New York, we are just beginning to delve into the fascinating relationship between nitrogen, plant spacing and bacterial diseases of onions. Our preliminary results suggest that reduced soil nitrogen and tighter plant spacing results in less bacterial decay. In this article, we report preliminary findings from exploratory studies and the observations that lead to these trials. We stress that we are not making recommendations at this time. However, we are hopeful that further studies will lead to specific recommendations.
Preventing Muck Soil Erosion by Reducing Tillage in Onion Production
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
The problem with using conventional tillage practices for onion production on muck soils is that it results in the subsidence of muck via wind and water erosion and oxidation of organic matter at a rate of one foot every 10 years, which is not sustainable for preserving these non-renewable natural resources for long-term productivity. Onions are one of the most valuable vegetable crops produced in New York State with the majority of the 13,000 acres being grown on muck soil. Producing onions using conventional tillage practices results in degradation of soil health and increased subsidence.
O-zone Injury on Vegetables
Crystal Stewart-Courtens, Extension Vegetable Specialist
Eastern New York Commercial Horticulture
Hot, humid weather with stagnant air masses may lead to ozone damage on crops. Ozone warnings were recently issued for much of New York. These warnings are intended for people with respiratory problems and let them know they should limit their outdoor activity and try to stay as much as possible in air-conditioned locations. These warning are also a good indicator that ozone damage may occur in plants.
Leek Moth Control and Information
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Leek Moth was detected in four home gardens in Plattsburg, NY in 2009. It was first detected in Ontario, Canada in 1997 where it has become problematic especially to small-scale, organic growers in eastern Ontario and to commercial producers in western Quebec, who have limited insecticides available to them.
Leek Moth continues its spread to more farms and gardens across the U.S., a new comprehensive website is available to aid in the identification and management of this pest. This Cornell website features maps of the distribution of leek moth, protocols on insect monitoring and identification, best management practices for farms and home gardens, a photo gallery of damage symptoms and a comprehensive resource section.
Visit the Leek Moth website.
Stop the Rot! - Using Cultural Practices to Manage Bacterial Diseases of Onion
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Narrow plant spacing reduced bacterial bulb decay by 53 to 64%
Do you know how easy this is? A simple modification to adjust your planting configuration is all it would take to drastically reduce losses from bacterial bulb decay. Our studies showed that when plant spacing was reduced from 6 or 8 inches to 4 inches with 3 or 4 rows per 3-foot plastic mulch bed (row spacing: 4 rows = 6 inch; 3 rows = 8 inch), this provided 53 to 64% control of bacterial bulb decay at harvest (Table 1). Marketable yield also increased by 1.4 to 2.4 times, representing an increased net economic return of $43 to $258 per 100 feet of bed, due to increased weight of marketable jumbo-sized bulbs (Table 1). We learned that wide plant spacing produces big bushy plants with more leaves, thicker necks, delayed maturity and bigger bulbs. Unfortunately, it was these bigger bulbs that rotted! By narrowing plant spacing, we got fewer colossal-sized bulbs, which we more than made up for by having significantly more healthy jumbo-sized bulbs to market (Table 1).
Alternatives to black plastic reduced bacterial bulb decay by 59 to 75%
This is also a very simple and easy modification for small-scale growers producing onions on plastic mulch to make to their cultural practices that could go a very long way towards reducing bacterial bulb decay. Our studies showed that reflective silver mulch, biodegradable black plastic and bare ground had significantly 1.8 to 2.8 times higher marketable yield than black plastic (Table 2). Reflective silver and biodegradable black plastics had significantly 3.7 and 3.6 times, respectively, higher jumbo weight than black plastic, which resulted in an increased net return of $96 to $215 per 100 feet of bed compared to black plastic (Table 2). All of the alternatives to black plastic had significantly lower soil temperatures compared to the black plastic; we suspect that the higher temperatures of the black plastic are more favorable for development of bacterial diseases.
Fall Application of Dual Magnum for Yellow Nutsedge Control in Muck Onions
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Yellow nutsedge (Cyperus esculentus L.) pressure is very high in certain muck areas where onions are grown. It appears to have become more of a problem in recent years. Onion growers and chemical company representatives believe that applying Dual Magnum, active ingredient metalochlor, in the fall can significantly reduce nutsedge pressure the following spring. However, weed scientists across the country do not believe that fall applications of metalochlor would have any effect on nutsedge populations the following spring, because the dissipation of metolachlor, is relatively rapid, 4-7 weeks in the northern United States. Dual Magnum is labeled as a fall application in field corn and soybeans only in Iowa, Minnesota, Minnesota, North Dakota, South Dakota and Wisconsin. For this use, there are restrictions on the label that state the date after which Dual Magnum may be applied, that soil temperature in the top 4 inches must consistently be 55°F and lower, and that tillage following incorporation must not exceed the 2-3 inch depth of incorporation.
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Upcoming Events
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Ontario Produce Auction
July 15, 2025
Stanley, NY
This evening meeting will demonstrate pest management in fresh market vegetables in both field and greenhouse (high tunnel) vegetables, primarily for those growing for wholesale auction. A hands-on demonstration of weed, insect and disease identification in vegetables including management options. Details on each topic will focus on field observations at the farm.
Orleans Summer Vegetable Meeting, 2025
July 16, 2025
Waterport, NY
Meeting themes are pest management in a wide array of produce and best practices for pesticide use. Professor Brian Nault will cover allium leaf miner and thrips in onions, garlic, and leeks, and discuss insect challenges in other crops. Bring your questions! We'll also have a field walk that includes high tunnel tomato and cucumber.
DEC credits available: 0.5 in CORE plus either 1.25 in 1a and 23, or 0.75 in 24.
Vegetable Pest and Cultural Management Field Meeting for Auction Growers -- Finger Lakes Produce Auction
July 18, 2025
Penn Yan, NY
This evening meeting will demonstrate pest management in fresh market vegetables in both field and greenhouse (high tunnel) vegetables, primarily for those growing for wholesale auction. A hands-on demonstration of weed, insect and disease identification in vegetables including management options. Details on each topic will focus on field observations at the farm.