Re: Dormant oil spray??/

K1MIZE@aol.com wrote:
> 
> Nan:
> 
> Dormant oil spray smothers insect eggs and overwintering insects, such as
> aphids.  Copper spray is primarily a fungicide.  I don't either one are in
> line with organic gardening principles.

 Kurt
I am not sure why you think these materials are "not in line with
organic principles" as most texts on organic growing approve of both as
being minimally disruptive to the environment.

However it is not organically correct just to make routine applications
without good reason.

Dormant oil spray is applied to deciduous fruit trees, as its name
suggests, only when they are leafless, as the oil can damage the
foliage. At one time some pretty fierce materials were used under the
name winter oil, but in recent years the main practice has been to apply
a material which is a straight paraffin oil. This is far less damaging
to vegetation and if suitably diluted can even be applied to trees in
leaf, making it useful for summer applications and for evergreens like
citrus.

Oil is used against insects and mites and acts purely mechanically by
smothering them. On fruit trees in winter it is mainly useful against
scale insects and the eggs of sucking mites and some insects which
overwinter on fruit tree bark. It is seldom necessary in an organic
orchard, but may occasionally be used if there are scales on the bark.
As to the eggs I mentioned, one is more likely to do harm than good if
the trees are under  an organic regime, as many of the eggs present will
not be of pests but of the useful creatueres which control them.

Copper, used in the form of Bordeaux mixture, copper oxychloride or
coppper hydroxide, has no effect on insects, but is used against fungus
and bacterial diseases. It is sometimes applied as a "cleanup" spray in
winter to kill spores of fungi on the bark, but once again organic
gardeners tend to keep off such spraying unless there is a specific
problem to deal with.

As to the different forms of copper, Bordeaux mixture, which has to be
specially prepared before use, is recommended in many treatises on
organic gardening, for no good reason hat I can see, except that making
up something seems more "natural" than getting it straight out of a
container. In my opinion copper hydroxide (sometimes sold as "kocide" or
supercopper") is the best form to use. Chemically it consists  merely of
copper, oxygen and hydrogen. Copper is a necessary element for plant
growth, but organic gardeners should use it sparingly, as in high
concentrations it can kill worms.

Regarding the possibility of worms being killed, spraying a tree results
in a surprising amount of the spray falling on the ground. It is very
instructive to spread a plastic under the tree being sprayed and observe
what it collects.

Moira



Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand
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