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Permalink What can you tell me about liquid copper as an organic fungicide?

Answer: Copper fungicides can be highly effective against disease and can extend the growing period, especially if applied before plants are infected with pathogen spores. However, copper fungicides can accumulate in the soil and cause health-related issues to plants and animals, including humans. Due to the effectiveness of cooper fungicides, in addition to the limited alternatives for specific diseases targeted by copper fungicides, such as Late Blight, copper fungicides are allowed for use in organic production systems.

Copper fungicides are classified as a synthetic on the National Organic Program National List. According to the National List (Subpart G), copper-based materials used as plant disease control must be used in a manner that minimizes accumulation in the soil and shall not be used as an herbicide. As a result of this classification, it is required by the certification process that before a copper fungicide is applied, farmers must first implement all available preventative and alternative practices and must show that such practices are ineffective. For many diseases, alternative practices include planting disease-resistant cultivars, destroying infected plants, managing irrigation, and implementing wide-row plant spacing.

If it is shown that all alternative practices prove ineffective, the use of any copper fungicide must be listed in the Organic System Plan and approved by the certifier. It is also recommended that frequent soil tests be performed to monitor cooper concentrations in the soil.

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