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  • Plant Pathology and Plant-Microbe Biology Section
  • Viticulture and Enology
  • Crops

The U.S. Environmental Protection Agency (EPA) is currently reviewing the registration of the fungicide Mancozeb, with proposed changes that may impact its use in grapes nationwide. This includes the potential removal of grapes from the approved label due to concerns about post-application worker exposure during activities such as hand-harvesting, leaf pulling, and tying. This article summarizes recent data from a 2024 Cornell-led survey and outlines what the proposed changes may mean for vineyards in New York and other Eastern states.

Why is Mancozeb under review? 

Mancozeb is a multi-site, broad-spectrum fungicide long used by grape growers across the U.S., especially in the humid climates of the East where fungal and oomycete diseases are a major concern. As part of its FIFRA-mandated re-registration process, the U.S. Environmental Protection Agency (EPA) has proposed cancelling grapevine as an approved use site for Mancozeb by 2027 (Docket EPA-HQ-OPP-2015-0291 and supporting document EPA-HQ-OPP-2015-0291-0094). This proposal is based on concerns about post-application worker exposure to residues during certain vineyard activities. For more information about this PID, please see Cornell Grape Pathology’s August 2024 article

The EPA identified specific tasks such as hand-harvesting, leaf pulling, and tying/training as high-risk if performed within 45 days of a Mancozeb application. These health concerns are considered as very serious by the EPA, and as such, they do warrant review and mitigation consideration. However, viticultural practices can vary significantly based on region, variety, and market segment. In response to the EPA’s proposed interim decision, Cornell Grape Pathology conducted a survey of 331 total grape growers, with 285 of whom self-identified as “Eastern grape growers,” which we defined as east of the Rocky Mountains. A full report of our survey data can be found here. The rest of this article will summarize and synthesize its findings. 

Why Mancozeb Matters in Eastern Vineyards

Eastern Vitis vinifera (European winegrape) vineyards face persistent pressure from Phomopsis cane and leaf spot, black rot, ripe rot, and downy mildew, especially in the early part of the season. Though this article mainly addresses vinifera grape concerns, there are numerous other diseases of vinifera, hybrids, and native grapes for which Mancozeb is a primary or critical fungicide for disease management. Mancozeb is:

  • A very effective product for control of Phomopsis, downy mildew, black rot, ripe rot, and numerous other diseases of grapes.
  • A low-cost, low-resistance-risk option for downy mildew.
  • A key rotation partner in resistance management programs.

Without Mancozeb, growers would likely need to rely more on single-site fungicides, which are often more expensive and at higher risk of resistance development. In New York, resistance in Plasmopara viticola (downy mildew) to multiple fungicide classes (FRAC 11, 40, and phosphonates) has already been documented.

Cornell Grower Survey: Key Findings

Our survey data found that many of the EPA identified post-application worker exposure risks may already be well managed in this region due to mechanization and viticultural habits. Our 2024 survey of 285 Eastern grape growers (including 188 from New York) revealed several important trends. While 96% of Eastern grape growers self-reported having used Mancozeb in 2024, 81% made their last application at or before bloom—typically by June. This means that later season high risk activities, such as hand harvest, would not occur within a 45-day hazard window. That said, some activities such as thinning and leaf pulling may still occur within a 45-day hazard window, warranting further consideration. 

Viticultural Habits Overview

Our survey finds that Eastern grape growers have predominantly mechanized viticultural management practices. Most of the grapevine grown in New York, including native varieties like Concord, Niagara, Catawba, and Diamond, as well as hybrids like Cayuga White, Marquette, Aravelle, Valvin Muscat, and Noiret, are typically managed mechanically. These varieties are grown widely in other grape-producing regions East of the Rocky Mountains. Additionally, grapevine production can be highly specialized to geographic region and varietal. For example, Muscadines and Norton, grapevine varieties grown widely throughout the Southeastern United States, are not thinned and are rarely leaf pulled. 

What the Survey Tells Us

The EPA's concern is grounded in health and safety—a priority shared by growers and researchers alike. However, region-specific production practices such as mechanization can reduce this risk. Our survey data found that most Eastern grape growers:

  • Apply Mancozeb only early in the season (until bloom), often more than 45 days before some high contact viticultural tasks occur.
  • Use mechanization for many vineyard operations that could occur within the 45 day hazard window (e.g., harvest, leaf pulling).
  • Most importantly, are willing to adapt where feasible to meet worker protection goals. 

Looking Ahead: Supporting a Managed Transition

If Mancozeb is eventually phased out, growers will need time, support, and proven alternatives. This includes:

  • Education on how to adjust management programs safely.
  • Access to effective replacements, including biofungicides and new chemistries.
  • Increased support for resistance monitoring and research on alternative strategies.

The EPA’s proposed Mancozeb decision reflects valid concerns that the grape growing community shares. Grape growers are open and willing to transition away from Mancozeb, if affordable and effective replacements are available. Recent trials by Cornell and partners have shown that rotations between conventional and biofungicides can achieve comparable control to full conventional programs, particularly for powdery and downy mildew. However, much is still yet unknown about how best to integrate biological products with fundamentally different modes of action from traditional chemistries into season-long disease control programs

In Eastern vineyards, where disease pressure is high and production is highly mechanized, Mancozeb continues to serve a valuable role. A one-size-fits-all approach to Mancozeb registration for grapevine may not reflect this reality. By integrating grower input, university research, and real-world data, we can move toward policies that protect both workers and crop sustainability.

For more detailed information, you can read Cornell Grape Pathology’s letter of commentary to EPA on behalf of the Eastern grape growing community, here: https://drive.google.com/file/d/1m17AFagIeB8MmsD3EGEg6k9nkNXQQys9/view?usp=sharing

About the author: Dr. Katie Gold is an Assistant Professor of Grape Pathology, and Susan Eckert Lynch Faculty Fellow, in the Plant Pathology and Plant-Microbe Biology Section of the School of Integrative Plant Science at Cornell University where she holds primary research and extension responsibilities for grape disease management in New York State. Dr. Gold’s Grape Sensing, Pathology, and Extension Lab at Cornell (GrapeSPEC) studies grape disease detection and management. The author thanks Dr. Phil Brannen for his thoughtful comments and feedback on this article.

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