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Viateur asks if I refer to plastic
pots. Wrong! When I write of clay pots, that is a defined
material. There are lots of plastics and I can't generalize for
all, although in my experience all the various plastic pots that I
have actually exposed to chlorine bleach have been chemically inert
towards it. I often clean my heavy plastic baskets with chlorine
and it works fine. I do not recall coming across specific comments in the
literature about the effectiveness of a water wash in removing residual bleach
chlorine and salts from [clay] pots well enough to prevent interference with
orchid growth. Has Viateur found any references to the contrary? I
have used this procedure for the past 20 years without problems. My good
friend Ray concurs with the effectiveness of the procedure [OGD V7 #245].
Perhaps I can use my post in the OGD as a future reference for those
who require them.
Plastic pots are permeated less well by
liquid and I would suppose they are even less injurious to plant growth after
chlorine treatment followed by a water rinse, provided the plastic is of a
type not affected by bleach.
As for the advantages of hose washing
the pots before soaking in chlorine, it would be prudent for keeping the soaking
bath from becoming laden with soil debris [chlorine does not react with silica],
but not absolutely necessary for viricidal effectiveness. What references
to the contrary are cited in AOS Bulletin
Dec 1972, p 1100?
As for trisodium phosphate [TSP] as a
viricide, this is ridiculous on its face. Despite the fact that it was suggested
in an old Orchid Bulletin, it does nothing that any other way of achieving a pH
of 13 would not accomplish, otherwise we would expect removing phosphate
from our fertilizers to promote orchid growth. For those who are
stubbornly inclined to go this route, I suggest a teaspoon of common lye to a
quart of water [more precisely 4 g lye/L] as a cheaper way of producing an
alkaline cauterizing solution, pH 13, without the bells and whistles. But it
would not solublize debris as does chlorine and it is so much slower in effect
that the danger of insufficient treatment becomes a factor. It would also
be more difficult to remove completely from porous clay pots
afterwards. Note that some chlorine gas is always in equilibrium with
bleach so that it would destroy infectious protein even across a gas barrier
such as an air bubble. Bert Pressman
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