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Copper Sprays: How they work and avoiding plant injury

Teresa Rusinek, Vegetable Specialist
Eastern New York Commercial Horticulture

June 7, 2018

You may be considering a copper spray to control or prevent certain diseases, particularly bacterial diseases in your crops.  Here's a quick review of 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., 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. 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.  A copper spray acts as a protectant fungicide/bactericide treatment, but lacks post-infection activity.

Because copper products come in different formulations and have different properties, it is important to read all the information on the labels. Besides rates, you will want to know about compatibility with other pesticides, adjuvants, and fertilizers.  Many growers are tank mixing biological fungicides and plant activators with coppers, while many are compatible, some are not, so make sure to check both labels for compatibility or call the manufacture/distributer for technical assistance.

The effectiveness of copper sprays has been correlated with the amount of elemental copper 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 Emeritus 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 phytotoxicity (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. Check the pH of your water source. 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 /solution in spray tank 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. Copper sprays generally cause more phytotoxicity when applied under slow drying conditions, such as when it's wet and cool.   Always read the label and follow copper tank mix partner label instructions.

For a comprehensive list of Copper Products Used for Vegetable Disease Control see:

http://vegetablemdonline.ppath.cornell.edu/NewsArticles/CopperFungicides2012.pdf

and for specific information on copper fungicides in organic disease management see:

http://vegetablemdonline.ppath...

Sources:  Dr. T. A. Zitter, Cornell University and  Dr. David A. Rosenberger, Cornell University

 

This article was published in the June 7th 2018, ENYCHP Vegetable News.  Click here to view the full newsletter.



 



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Upcoming Events

High Tech Precision Orchard Spraying

July 20, 2020

Join us the afternoon of July 20th to learn what's new in orchard precision spraying technology. We'll be joined by Dr. Jason Deveau, Dr. Heping Zhu, and Steve Booher.  After their presentations, we will open up the meeting for all three presenters to field questions and comments. 

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Announcements

U-Pick Farm Practices During Covid-19 Pandemic

U-Pick is a critical direct marketing approach for many of our farms and provides
customers with a unique connection to fresh produce grown close to home. In light
of what we understand about the spread of COVID-19, new management practices
will be needed to protect your farm team and your customers. This document
provides recommended practices and communication strategies for U-Pick
operations for the 2020 season.

https://rvpadmin.cce.cornell.edu/uploads/doc_864.pdf

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

2020 Biweekly Vegetable News Podcast - Episode 6 7/1/20

July 2, 2020
The July 1st, 2020 edition of the Eastern New York Vegetable News covers the following topics:

Cucurbit Downy Mildew Update (1:05)
Changes to the Paycheck Protection Program (9:10)
Managing Caterpillar Pests in Brassicas (12:53)
Strawberry Renovation (17:56)
Developing a Safety Plan to Comply with NY Forward Phased Re-Opening Requirements (24:12)

Here are links to additional resources mentioned in the episode:

NY Forward Safety Plans
Introductory “how to” video for writing your plan:
https://www.youtube.com/watch?v=V2PH3wCgdhc&feature=youtu.be

Cornell Agricultural Workforce Development NY Forward business safety plan support for farms
https://agworkforce.cals.cornell.edu/ny-forward-business-safety-plan/
• Plan templates
• Guidance and considerations for plan writing
• Links to “how to” videos
• Links to additional resources such as log templates, hand washing station plans, and more
• Webinar recordings

NYS Department of Agriculture and Markets novel coronavirus page: Guidance documents for farm businesses in multiple languages
https://agriculture.ny.gov/coronavirus

Strawberry Renovation
For more in-depth information re: strawberry renovation, visit http://www.hort.cornell.edu/fruit/nybn/newslettpdfs/2014/nybn1306.pdf.

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