[aroid-l] amorph tuber rot problems

Hello:  The best of the New Year to everyone and I enjoy the list immensely.
I have discussed this problem with a few of you already, off list, but
thought that I would bring it up again, as it is continuing to plague me:  I
am trying to raise Am. paeoniifolius in some quantity for a few years now.
I have been growing in containers, and I am having a continuing problem with
a 'soft-rot' of tubers after harvest.  I had some pathology work done on
some of infected tubers last year and both Rhizopus and Verticillium spp.
were found (fungi).   The problem typically appears a week or two after
harvest, mostly afflicting larger tubers (> 10 cm dia).  I find it mostly
ineffective to try and 'salvage' infected tubers: if I drastically cut away
the infected portion and coat with fungicide, the lesions continue to
spread.  I altered my growing strategy in several ways this year: 1) brand
new  potting soil (no more 'reuse' of soil), 2) regular soil drenches with
fungicide (Mancozeb)- 4-5 times during the growing season, 3) drench tuber
in fungicide after harvest.  I am growing to dormancy and handle the tubers
with the greatest care during and after harvest (stored cool and dry).
However, the problem continues, to a lesser degree perhaps, but still very
disconcerting. I suspect that one error I am making is using a soil mixture
that is not well enough drained, but I can't believe that with all of the
fungicide that I am still experiencing this.  Of course, here in Florida
where 10 cm of rain may fall on a July afternoon, a 'well-drained' mixture
may not apply!   Any and all ideas welcome!  Many thanks!

D. Scott Taylor, Ph.D.
Brevard County Environmentally Endangered Lands (EEL) Program
Central Region Land Manager
5560 North US Highway 1
Melbourne, FL 32940
tel: 321.255.4466
FAX: 321.255.4499
email: staylor@brevardparks.com
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