In article ,
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
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