Anyone familiar with spraying copper on plants to control mildew/black spot?
Question:Because that's what I just did for my squash and tomatoes, which I read about in here, and was recommended by the organic gardening specialist at the nursery. I was wondering if you have to wait a certain amount of time before you harvest anymore vegetables, because I know you have to wait 7 days with certain other fungicides.
Answers:
Here is a excellent guide from Cornell University on Copper fungicides. You do need to wash your vegetables before consumption. Check the label for the specific wait time to harvest. It can vary from one product to the next.
http://www.nysaes.cornell.edu/pp/resourc...
Here are some interesting facts about copper based fungicides:
Some mixtures, such as oil and copper products, are strongly phytotoxic to some crops. For instance, citrus and apples have little tolerance, while this combination is sometimes used on tomatoes without damage.
Handle copper products with care.
The re-entry interval (REI) is 24 hours for Champion WP®. Re-entry intervals where created for farm worker safety, but they do give you a good indication of the danger a fungicide presents. This was also true for at least 3 other copper based fungicides I looked-up.
Copper is a necessary plant and animal nutrient, but it is toxic to plants and other organisms at high levels. Maximum soil concentration rates for copper in New York soils have been recommended based on soil type, from 40 ppm (sandy soils) to 60 ppm (silt loam) to 100 ppm (clay soils) in order to protect against phytotoxicity and negative impacts on soil life (Harrison et al. 1999). Typically, each spray with a copper-based fungicide results in an application of 1 to 4 lb. of copper per acre (raising the topsoil concentration from 0.5 to 2 ppm), and often several copper sprays are made per season. Thus, under a heavy copper spray program, toxic topsoil levels could be reached in a matter of decades.
Copper sulfate is practically nontoxic to birds.
Copper sulfate is highly toxic to fish. Even at recommended rates of application, this material may be poisonous to trout and other fish, especially in soft or acid waters.
Bees are endangered by Bordeaux mixture. Copper sulfate may be poisonous to sheep and chickens at normal application rates. In some orchards, most animal life in soil, including large earthworms, has been eliminated by the past extensive use of copper containing fungicides (Extoxnet 1996). Copper has been found to suppress rates of nitrogen fixation by the bacteria Rhizobium under some situations at relatively high copper levels of 235 ppm (OMRI 2001). Earthworms are sensitive to several heavy metals and may accumulate them in their tissues.
Ingestion of copper sulfate is often not toxic because vomiting is automatically triggered by its irritating effect on the gastrointestinal tract. Symptoms are severe, however, if copper sulfate is retained in the stomach, as in the unconscious victim. Injury to the brain, liver, kidneys, and stomach and intestinal linings may occur in copper sulfate poisoning. Copper sulfate can be corrosive to the skin and eyes. It is readily absorbed through the skin and can produce a burning pain, as well as the other symptoms of poisoning resulting from ingestion. Skin contact may result in itching or eczema. It is a skin sensitizer and can cause allergic reactions in some individuals. Eye contact with this material can cause conjunctivitis, inflammation of the eyelid lining, cornea tissue deterioration, and clouding of the cornea (Extoxnet 1996).
Vineyard sprayers experienced liver disease after 3 to 15 years of exposure to copper sulfate solution in Bordeaux mixture.
Copper sulfate has been shown to cause reproductive effects in test animals.
Long-term animal studies indicate that the testes and endocrine glands have been affected (Extoxnet 1996). Heart disease occurred in the surviving offspring of pregnant hamsters given intravenous copper salts on day 8 of gestation.
I am not fond of chemical fungicides due to all the warnings on them.
Milk and water will treat it. I've used it on Phlox and Roses with good results.
Read all about it:
http://www.pioneerthinking.com/tv-mildew...
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