Bordeaux Mixture
Bill Robinson
The question was raised about Bordeaux Mixture. It is
a mix that has been around for many, many years and
it has a reputation of being both effective and
environmentally friendly. It is a slury of "bluestone" (copper
sulfate) and lime although there are some variations
based on lime and copper hydroxide.
Bordeaux is an effective fungicide and works both as a
material to prevent infections from happening and as a
control material to treat established infections. It is also a
pretty fair miticide. It is used on fruit trees, grapes and
some truck crops. "Pests of the Garden and Small Farm"
by Mary Louise Flint says,
". . .Controls brown rot and shot hole diseases in tree fruit.
Controls some grape diseases. Also controls apple scab,
blotch, apple black rot, melanose, anthacnose, early and
late blight of potatoes and tomatoes, downey mildew, fire
blight, leaf spot, peach leaf curl and many other fungal diseaases".
The problem with Bordeaux is that it can burn if applied when
there are high temperatures and there is some threat of loading
the soil with toxic copper if you use too much, too often.
Bordeaux has been used for so long and by so many people
without problem to the environment that it is considered O.K. in
most organic programs. It is allowed for use on certified organic
crops by most certification agencies. The LD50 is 300 which is
the same as diazinon so it does warrent some caution in the use.
The question was also raised as to whether it is possible to grow
a fruit orchard organically when the orchard is surounded by
orchards using synthetic pesticides. I think that at bottom line you
can get as good a level of control with "organic" materials" ,which
would include Bordeaux, as you can with synthetic pesticides but it
may take a bit more labor and may carry a bit more blemish. The
flip side is that fruit from an organic orchard will usually be of a
better quality with a better flavor and, if marketed, getting a
better price.
Bill
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