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Taking a year off, diseases, what to do?
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songbird wrote: Steve Peek wrote: ... Spray with copper, start early and spray often. I've had very good success on my heirloom tomatoes with this method. copper is a poison to many creatures. i would not advise this at all. fungal problems can be controlled in many other ways that don't involve poisons. songbird I'd echo The Cook's advice. http://www.csrees.usda.gov/Extension/index.html http://aggie-horticulture.tamu.edu/p...problemsolver/ Additionally I'd suggest that you do rotate the beds in which you plant your crops. Because you said that the problems developed slowly (over several seasons), soil pests would seem to be a reasonable guess. If it is a mold that is dedicated to one family of plants, it won't travel quickly. I replanted my plants in the same beds for years before my garden got bitten by soil problems (wilt). Since you haven't used copper before, you might try it, but it will upset the soil ecology. If you get a healthy ecology growing in your garden soil, it will make it difficult for pathogens to establish themselves. Fungi and mycorrhiza are important to healthy soils. http://www.extension.org/pages/18351...-late-blight-o f-potato-and-tomato-with-copper-products Copper does not degrade in soil and there are serious concerns about the cumulative effect of copper applications on soil copper contents and soil biology. In the European Union, copper fungicides have been banned completely in the Netherlands and Denmark, and use has been restricted to 6kg/ha/year (5.4 lbs/A) elemental copper in other EU countries since 2006. These regulations were directed at perennial cropping systems in which copper applications are made annually, resulting in a high likelihood of soil copper accumulation, but the regulations also apply to annual cropping systems. In annual rotational systems, where copper applications are only made every 4-6 years, copper accumulation is less of a concern, but nonetheless, copper use is regulated and certified organic farmers in the US are required to restrict their use of copper products. Copper fungicides are protectants, so they MUST be applied to the foliage before infection. The copper ion is absorbed by the germinating spore, and the copper denatures spore proteins. Once infection has occurred, copper has no effect on disease progress in the plant. Because there is no 'kick-back', coppers must be applied regularly throughout the potato production season, beginning when potato plants emerge. In some regions, this strategy can result in 8 or more sprays per season. In dry conditions, coppers stick well to plant surfaces without adding a sticker to the tank mix, so when plants are not growing, sprays could be less frequent. However, when the potato foliage is growing rapidly, applications are required more frequently in order to protect new foliage. In the European BlightMOP project, potato late blight was effectively controlled with as little as 6 sprays of 0.9 lbs elemental copper per acre each as oxychloride, and this total application rate (5.4 lbs Cu per A) fell within the EU guidelines (6 kg/ha, or 5.4 lbs/A). In a single season field trial at Oregon State University in 2008, four applications of 1.9 lbs elemental copper as cupric oxide (highest label rate, Nordox) (total Cu application: 7.6 lbs Cu/A) strongly suppressed disease development (Stone, 2007). It is possible that Nordox could be effective at 0.9 lbs elemental copper/A per spray. Monterey Chemical, the US distributor of Nordox, is currently investigating the efficacy of lower Nordox rates. Toxicity to plants (this section is excerpted from Resource Guide for Organic Insect and Disease Management) Copper is toxic to plants, particularly in large doses and at high temperatures. Symptoms of excess copper are reddish-brown leaves, followed by an uneven yellowing. These leaves will wilt and become dessicated. Leaves in this condition are also more susceptible to frost damage. Copper toxicity rates may result in reduced fruit set of tomatoes and in extreme conditions may even kill plants. Copper will be more toxic to plants in acidic conditions and more effective against disease under higher pH conditions, so a program to maintain soil pH is an important part of a strategy to maintain plant health. Soil accumulation (This section is excerpted from Resource Guide for Organic Insect and Disease Management.) Because copper accumulation is practically irreversible, limitations on copper use is a serious concern for organic farming. Copper is bound, or adsorbed, to organic materials, and to clay and mineral surfaces. The degree of adsorption to soils depends on the acidity or alkalinity of the soil. Because copper sulfate is highly water soluble, it is considered one of the more mobile metals in soils. However, because of its binding capacity, its leaching potential is low in all but sandy soils (Extoxnet 1996). Copper is a necessary plant and animal nutrient, but it is toxic to plants and other organisms at high levels. It is always present at a background level, but can be of concern in situations of heavy agronomic use of copper compounds. Agricultural soils are reported to have average background levels of 20-30 ppm (Baker 1990), with average overall US level found to be 15.5 ppm (Holmgren 1993). Some vineyard soils in Europe, which have seen intensive use of copper sulfate containing Bordeaux mixtures for 100 years, have soil Cu concentrations ranging from 100 - 1500 ppm (Besnard 2001). 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. Some certifiers recommend that growers include copper in their soil testing program in order to determine a background level and track any changes in that level as a consequence of repeated copper spraying. -- - Billy E pluribus unum http://www.rollingstone.com/politics/news/the-great-american-bubble-machine-20100405 |
#2
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Taking a year off, diseases, what to do?
Billy wrote:
about copper. thanks, useful information in there. songbird |
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