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  amorph tuber rot problems
From: "Scott Taylor" staylor at brevardparks.com> on 2004.01.02 at 13:46:13(10978)
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

From: rajshekhar misra rajshekharmisra at yahoo.com> on 2004.01.02 at 21:19:18(10979)
Dear Dr.Taylor
A very happy new year. Tuber rot in A.paeoniifolius is
a serious problem at times. I am sure you may be
starting with healthy planting material. The soil
should be certainly well drained. Please check for
nematode population in the potting mixture.
Meloidogyne incognita infests the roots and tubers
paving way for a lot of secondary pathogens. If you
can afford to discard the infected planting material
and start with fresh planting material providing
proper soil drainage, the problem could be controlled.
From: "Petra Schmidt" petra at plantdelights.com> on 2004.01.04 at 07:19:52(10981)
Hello Scott,
Are you letting the tubers dry off completely before placing them into cool
storage? And have you tried storing them in warmer temperatures (what is
your cool storage temp?). I've seen tuber rot become a real problem with
wet cold conditions during dormancy and even during the leaf collapsing
pre-dormancy stage; we're getting tubers out of ground beds or out of cool
wet growing conditions to let them dry off in dry warmth and light before
placing them into winter storage. Our winter storage is about 45 degrees F
and dry.
Have you tried using a powder fungicide, instead of a drench, after harvest?
Again, keeping the tubers as dry as possible once they're out of the
ground/pots is critical, in my growing experience here in North Carolina...a
liquid drench at the end of the growing season would not be a good idea here
but coating the suspected problem tubers in powdered fungicide and letting
them dry off is a better option here.
Keep us posted, please...

From: "Scott Taylor" staylor at brevardparks.com> on 2004.01.05 at 07:20:20(10986)
Dr. Misra: Thank you again for your kindly response. As you might recall,
you had sent me an extensive correspondence last year when I was researching
this problem. I have followed much of your advise, but think that I am
still making a mistake in trying to 'reuse' damaged tubers (which I hate to
discard!). I did not separate plantings from damaged material from 'good'
material, so it could be that the recurrent problems are from that diseased
material that was reused. I do not see the typical evidence of nematode
infections (blisters, etc.) but that is something I should check further. I
will try and keep better track of this next year. Thank you again!

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