Arisaema Rust

Paul Christian paul at RAREPLANTS.CO.UK
Sat Aug 9 20:14:47 CEST 1997

Hi All,

As far as I am aware, rusts are host specific.  We are not talking of just
rust, we are as an example, talking of Hollyhock Rust, Arisaema rust etc. If
your Hollyhocks are 'rusty' your Arisaemas will not fall to it, as it is
Hollyhock rust.

The second thing about (?most/all?) rusts is that they actually need TWO
hosts to complete their life cycle, they have a phase on each host
alternately.  If one host is missing then the other will not fall to rust.
To take this further eliminate one host and the infection on the second will
not come about. This was the thinking behind the attempt in the US to
eliminate berberis as it is a secondary host of a rust that afflicts one of
the major food crops, wheat I think, but it is perhaps not important.  The
attempt failed but it was politically inspired and half-baked, rather than
powered by a full scientific study.

It may be that in parts of the US or Canada, that the other host for the
Arisaema rust is missing, so Rand could find that his Areisaemas appeared to
immune to rust, Jim's might not be.

This by the way is old back of the brain botany, I hope I am not wildly out
with modern thinking !

Treatment, don't know BUT. I have annual infections here on Dactylorhiza
incarnata (an marsh orchid), the secondary host is willow, normally I guess
Salix repens, with which it is usually associated in the wild strange to
say. I treated this year by hand picking of obvious infection as soon as
some was noticed, and then dunking of the living plants in a x4 strength
solution of Benlate (Benomyl), mixed with x4 strength Supercarb
(carnbendazim plus activator).  2 hours at room temperature.

I have dead areas of leaves but NO infection, not a trace. I put the dead
leaf areas down to areas infected and perhaps killed, but in which the
infection itself has vanished.  This may be Doc Christians coloured Medicine
Water, I dont know.  I would stress that this may not be a cure, I have only
one year's results, but at the same time I have no rust at all whatsoever -
period. full stop.

my intended two pennyworth (2c) must be at least a pound now ($1.63 !) I
will shut up

Paul :-))

Paul Christian   - Rare Plants
Internet Site    -
e-mail           - paul at  (or bulbs at
Telephone        - (+44) 01978 366399
Fax              - (+44) 01978 366399
Snail Mail to    - Dr. P.J.Christian,
LL13 9XR, UK

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