Re: molds
- Subject: Re: molds
- From: T* &* M* R*
- Date: Tue, 24 Apr 2001 15:38:39 +1200
Beverly Fizzell wrote
always thought mold was a bad thing. Not so? B
It is horrible if you have an allergy to it. Pharmaceutical
companies use it to make Penicillin. So, it
depends....
ann
"Mould" is just a popular general term for any growth of fungus over
other material, be it plant or animal tissues or merely your bathroom
tiles or shower curtain. Some moulds are good and others are not, each
needs to be examined in context. For instance, mould on a ripe fruit
indicates a fungus which is busy recycling it. Because it is digesting
the fruit tissues they will no longer be nice to eat, but the mould is
not intrinsically bad, just following natures's imperative to get the
organic material back into circulation (as of course you would encourage
in a
compost heap). Some of the group of moulds, which one finds for instance
on decaying citrus, are blue or green in colour and belong to the group
which Ann
mentions as causing allergies in susceptible people. These are bad for
sensitive
people like Ann, but mostly no trouble to the rest of us. They are
certainly
potentially useful, as she also says, to Pharmeceutical companies (and
as Jim has reminded us to the cheese makers!)
A generally "bad" type of mould is the thick white fluff one may
sometimes find on a bean pod or a carrot which has been stored in humid
conditions. This is the mycelium of a fungus (Sclerotinia sclerotiorum)
which is a definite pathogen of several different vegetables. Once
introduced to a garden it may live on in the soil and attack not only
beans and carrots, but tomatoes or potatoes also. Fortunately it is most
commonly deactivated in richly organic soils by the protective fungi
which police them.
Powdery Mildew I suppose might be called a mould, as it produces a web
of mycelium crawling over leaf surfaces and from this buds off huge
masses of rather floury-looking spores. Because it has the unique habit
of growing on the outside of leaves rather than inside, it is easy to
attack it, and the latest treatment of applying diluted low-fat milk
(one part milk to 2 parts water) seems to be best and easily controls
it.
Then there is black mould, which is unsightly but harmless to the shoots
of plants, on which it so often lives. This is a very lowly one-celled
organism, so lowly that there are arguments whether it is a fungus or an
alga (but this is of merely academic interest). What is interesting to
practical people is what it indicates, for it grows wherever there is
sugar availble to eat and wherever there are sucking insects operating
there will be sugary exudate spattering the leaves and stems below their
colonies. So to get rid of this unsightly mould one first needs to
remove whatever pest is providing it with a living. Once the pest is
gone the mouldy leaves can be gently wiped with a damp cloth or rubbed
with the fingers following a good hosing and abrecadabra! the undamaged
green surface will once more emerge.
As to the white mould Bev has found on her compost, many people do not
seem to be sure about the exact identity of the organisms which make raw
plant and animal remains into fine black compost. I think most are
probably vaguely aware that bacteria are involved, and indeed they are
largely responsible for the early part of the complicated process, at
least all the part which involves a noticeable rise in temperature. Once
this stage is over and the material cools the rest of the process
involves a variety of workers among which fungi are prominent, and also
a rather similar-looking group of organisms known as Actinomycetes.
Either of these can form white threads thick enough to be easily visible
to the naked eye, and that Bev is what I presume you are seeing in your
compost. By the time the process is completed these will have
disappeared and should not be noticeable in a mature sample. That they
_are_ present as you mention indicates a very healthy compost heap with
plenty of willing workers - there should be some good stuff available in
a month or two!
While most of these organisms are harmless, as Ann has aready said and
Sandra reiterated, the spores of certain moulds can be irritant or
positively dangerous and some of these can sometimes occur in a compost
heap. The one which springs to mind is the organism causing Legionnairs
disease. Following a case in Australia of a woman apparently contracting
this from inhaling dust from a bag of compost, all compost purchased
here (and no doubt in Oz) carries the warning to be careful not to
breath in the dust and to wash carefully after handling the product.
This problem seems to be very rare, but nevertheless one must be aware
that even natural materials are not necessarily wholly benign and should
be treated with respect.
As to the flooded building which gave you such a bad image of moulds,
unfortunately this sort, even small spots of black mould on walls or
tiles or furnishings, are indeed mostly manevolent and destroying to
property, and they are the ones most likely also to be resposible for
allergies and other human ills, so you are quite justified in having a
bad image of them. In some old woodwork one may find a type of mould
lacking the bright colours and instead just producing lots and lots of
white mycelium. This is the dreaded dry rot, which is as efficient as
termites in destroying wood. It is not however, as far as I know,
dangerous to humans.
Think that is most of 'em!
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata (near Wellington, capital city of New Zealand)
