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How Copper Sprays Work and Avoiding Phytotoxicity

June 26, 2013

How Copper Sprays Work and Avoiding Phytotoxicity
Copper has been widely used in both conventional and organic production for some time. Copper was one of the first elements used as a plant fungicide (the other was Sulfur). Its discovery can be traced back to the famous origin of Bordeaux mixture, containing a mixture of copper sulfate (CuSO4) and slaked lime, and used for downy mildew control in French vineyards.

Recently, growers have asked me questions regarding the mode of action of copper and had  concerns about phytotoxicity. First, let's begin with how copper controls pathogens. Copper is usually applied in the fixed form which lowers its solubility in water. Fixed coppers include basic copper sulfate (e.g., Cuprofix Ultra Disperss), copper oxide (e.g., Nordox), copper hydroxide (e.g., Kocide, Champ), copper oxychloride sulfate (e.g., COCS), and copper ions linked to fatty acids or other organic molecules (e.g., TennCop, Cueva). The spray solution is actually a suspension of copper particles, and those particles persist on plant surfaces after the spray dries. Copper ions are gradually released from these copper deposits each time the plant surface becomes wet. The gradual release of copper ions from the copper deposits provides residual protection against plant pathogens. At the same time, the slow release of copper ions from these relatively insoluble copper deposits reduces risks of phytotoxicity to plant tissues. Copper ions denature proteins, thereby destroying enzymes that are critical for cell functioning. Copper can kill pathogen cells on plant surfaces, but once a pathogen enters host tissue, it will no longer be susceptible to copper treatments. Thus, copper sprays act as protectant fungicide/bactericide treatments, but lack post-infection activity.

Because different formulations have different properties when used as spray materials, growers need to learn how to read and interpret labels. The effectiveness of copper sprays is highly correlated with the amount of elemental copper that is applied. The metallic copper content varies widely by product. Potency also varies by how the product is prepared. Finely ground copper products are more active than coarsely ground ones. Professor Tom Zitter of Cornell University suggests that for vegetable crops. Begin by choosing a copper product with at least 20% or more copper as the active ingredient to insure the greatest release of copper ions.

There are several suggestions for avoiding phytoxicity (or plant injury) with copper sprays. Limit the copper ion concentration on plant surfaces by using copper products that are relatively insoluble in water, i.e. fixed copper. Copper can accumulate to high levels on plant tissue when sprayed repeatedly to cover new growth and there is no rain. In this situation, after a rain event, a large amount of copper ions may be released leading to phytotoxicity. Solubility of fixed coppers increases under acidic conditions. Copper sprays will become more phytotoxic if they are applied in an acidic solution. Most copper products are formulated to be almost insoluble in water at pH 7.0. As the pH of water decreases the solubility of the copper fungicides increases and more copper ions are released. If the water used is too acidic (below pH 6.0-7.0 depending on the copper formulation) excessive amounts of copper ions could be produced which may cause damage to fruit and foliage. Formulations vary in solubility hydroxides are more soluble than oxychlorides which are more soluble than tribasic copper sulphates and cuprous. Less soluble formulations are usually more persistent. Check the pH of your water source. Copper sprays generally cause more phytotoxicity when applied under slow drying conditions, such as when it's wet and cool.  Always read the label instructions follow the Copper and tank mix partner labels.
For a comprehensive list of Copper Products Used for Vegetable Disease Control see
http://vegetablemdonline.ppath.cornell.edu/NewsArticles/CopperFungicides2012.pdf


Sources: T. A. Zitter, Cornell University Department of Plant Pathology & Plant-Micrbiology and David A. Rosenberger, Professor of Plant Pathology, Cornell University's Hudson Valley Lab


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Ethnic Vegetables

Ethnic Vegetables

Garlic

Garlic

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Horseradish

Horseradish

Kohlrabi

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Leeks

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Lettuce / Leafy Greens

Lettuce / Leafy Greens

Melons

Melons

Nectarines

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Onions

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Parsnips

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Peaches

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Pears

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Peas

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Plums

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Potatoes

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Pumpkins / Gourds

Pumpkins / Gourds

Radishes

Radishes

Raspberries / Blackberries

Raspberries / Blackberries

Rhubarb

Rhubarb

Rutabaga

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Snap Beans

Snap Beans

Squash - Summer

Squash - Summer

Squash- Winter

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Upcoming Events

Champlain Valley Fruit Set Thinning Meeting

May 28, 2024 : Champlain Valley Fruit Set Thinning Meeting

Mike will review his observations from the field, and we will then hear from Dr. Robinson about his thinning suggestions for the 10-12mm thinning window. We will then hear from Dr. Anna Wallis, Dr. Andres Antolinez, and Dr. Scott Cosseboom for pest management updates.  

To join, simply click on the zoom link at 3PM on Tuesday: https://cornell.zoom.us/j/93411218328?pwd=RUpFNlY3Nm5nS0tkUjdDWEU0cklCdz09

View Champlain Valley Fruit Set Thinning Meeting Details

June Produce Field Meeting

Event Offers DEC Credits

June 5, 2024 : June Produce Field Meeting
Fort Plain, NY

Come join us for a discussion on greenhouse production, IPM techniques in the greenhouse, and a discussion of IPM strategies for tomatoes, cole crops and cucurbits. 

Meeting is free and open to the public.

2 DEC credits in categories 1A and 23 are available. 

View June Produce Field Meeting Details

Weed Management in Perennial Fruit Crops - Field Workshop

Event Offers DEC Credits

June 20, 2024 : Weed Management in Perennial Fruit Crops - Field Workshop
Tivoli, NY

Join us on the morning of June 20th as we hear from Cornell University weed management specialists Dr. Lynn Sosnoskie and Dr. Yu Jiang, who will discuss their recent research on autonomous orchard weeding systems.  

We will also hear from Mike Basedow of CCE ENYCH and learn about the ongoing results of herbicide research trials he is conducting.  Bryan Brown of NYS IPM will discuss pre-plant preparations and mulches that could be useful for controlling weeds without herbicides.   

Identifying the differences between weed species and key differences between annuals and perennials that factor into management will also be covered.     

This workshop is FREE to attend, but we ask that you please register ahead 

View Weed Management in Perennial Fruit Crops - Field Workshop Details

Announcements

2023 Spotted Wing Drosophila Monitoring/Management

All berry farmers are watching for monitoring reports that indicate Spotted Wing Drosophila (SWD) adults are in their region. Mid-season berry crops should be sprayed as soon as berries begin to ripen unless you've elected to use insect exclusion netting.

- For general information about SWD, and to enroll for free monitoring reports, visit the Cornell SWD blog https://blogs.cornell.edu/swd1/.
- Click here for the 2023 Quick Guide for Pesticide Management. 
- For some great instructional videos and fact sheets on insect exclusion netting, visit the University of Vermont's Ag Engineering blog.


Resources from CCE ENYCHP!

We are developing new ways to connect with the CCE ENYCHP team this year! We have a Youtube page located at this link. Check out videos on Table Grape Production, Pest Updates and the 20 Minute Ag Manager - in 4 Minutes series

We have a Facebook Page here as well as an Instagram page. We keep these places updated with current projects, events, and other interesting articles and deadlines.

There are also text alerts available. Fruit and vegetable farmers in 17 Eastern NY counties can now receive real time alerts on high risk disease and pest outbreaks texted directly to their cell phone. The Eastern NY Commercial Horticulture program, which is supported by local Cornell Cooperative Extension associations, will now offer text alerts to those that enroll in our program in 2019. 

The text alerts will be reserved for important crop alerts that could impact management decisions immediately. For instance, if there were an outbreak of Late Blight in the area, this would be transmitted to vegetable growers.

Farmers can choose the crop for which they wish to receive updates. Additionally they can request that Ag Business Alerts be sent to them. These alerts might include due dates for crop insurance deadlines, market opportunities etc.

If you have questions, please contact enychp@cornell.edu


Podcasts

Winter Greens Grower Interviews in Northern New York

October 22, 2022
In this episode, vegetable specialist Elisabeth Hodgdon interviews Lindsey Pashow, ag business development and marketing specialist with the Cornell Cooperative Extension Harvest New York team. They discuss findings from a series of interviews with winter greens producers in northern New York. Lindsey shares production and marketing challenges associated with growing winter greens in this cold and rural part of the state, success stories and advice from growers, and tips for those interested in adding new crop enterprises to their operation.

Funding for this project was provided by the Northern New York Agricultural Development Program. The episode was edited by Miles Todaro of the ENYCHP team.

Resources:
• Crop enterprise budget resources available from Penn State Extension (field and tunnel vegetables: https://extension.psu.edu/small-scale-field-grown-and-season-extension-budgets), UMass Extension (winter spinach budgets: https://ag.umass.edu/vegetable/outreach-project/improving-production-yield-of-winter-greens-in-northeast and field vegetables: https://ag.umass.edu/vegetable/fact-sheets/crop-production-budgets), and Cornell Cooperative Extension (high tunnel vegetables: https://blogs.cornell.edu/hightunnels/economics/sample-budgets-spreadsheets/). Use these budgets as templates when developing your own crop enterprise budget.
• The Organic Farmer’s Business Handbook, by Richard Wiswall
• The Winter Harvest Handbook, by Eliot Coleman

For questions about the winter greens project discussed in this podcast, reach out to Lindsey Pashow (lep67@cornell.edu) or Elisabeth Hodgdon(eh528@cornell.edu).

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