From: Tony Avent tony at plantdelights.com> on 2006.07.09 at 14:53:28(14397)
Adam:
I'd venture a guess that your culprit is a bacterial soft rot, Erwinia.
If so, fungicides are useless. I have seen this devastate collections
of certain amorphophallus species under certain conditions. It seems to
be worse when there is little air movement, lots of moisture, and high
humidity. I have even heard theories that it can be spread by the hands
of those who have handled tobacco or tobacco products. You will find
many references by using a Google search.
Tony Avent
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Plant Delights Nursery @
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9241 Sauls Road
Raleigh, North Carolina 27603 USA
Minimum Winter Temps 0-5 F
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email tony@plantdelights.com
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phone 919 772-4794
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"I consider every plant hardy until I have killed it myself...at least three times" - Avent
Adam Black wrote:
We are suddenly having a severe problem with the Amorphophallus
species at the botanical gardens where I work. We are seeing a
localized rotting of the base of the petiole an inch or two above the
soil line that turns the petiole base to jelly and topples the leaf.
It is affecting all three species we have - A. konjac, A. bulbifer,
and A. paeoniifolius, and is occurring in various areas of the gardens
that are seperated by a considerable distance and have been otherwise
healthy in thier locations in the ground for years. I started noticing
it in the konjacs and the bulbifers a month or so ago shortly after
they put up thier leaves, and the rate of loss has escalated from
there. I just now noticed on the late emerging paeoniifolius that most
of them have early signs of this infection. I am by no means an expert
on fungi, but there are several different colors of fungus on the
affected areas, but I am not sure if this is secondary or not. The
infection starts out as a brown patch on the base of the petiole a few
inches above the soil/leaf litter line, and this progresses around the
petiole and inward, but does not spread up or down the petiole from
that point. I dug up one corm from an infected A. bulbifer and it
appeared shrunken in and clearly unhealthy, felt softer than a healthy
corm but no external evidence of rot was evident. I did not cut it
open to see what it looked like inside, but plan to on another
specimen this week.The base of the petiole below where the leaf had
rotted off was still healthy in appearance and firmly connected to the
corm.
Curiously, I have yet to see it affect any similar aroids growing
side-by-side with affected Amorphs in the gardens including Typhonium
venosum (of which we have many plants), Gonatopus bovinii, Remusatia
vivipera, and our native Arisaema triphyllum and jillions of Arisaema
dracontium. The Amorphs affected include both potted specimens and
those situated in the ground for years, and among the potted specimens
some affected plants are in a greenhouse with controlled watering,
while other potted plants are exposed to the weather in addition to
supplemental irrigation. I am keeping a closer eye on it now, but the
infection appears to spread and rot through the petiole relatively
quickly, so that the leaf itself still looks unstressed and perfectly
healthy after it has rotted off. I have only worked here since this
past winter, but the gardens director remembers a few Amorphs having
this problem last year but didn't think much of it, as the hundreds of
others in our mass plantings looked fine. If I had to guess now, I
would say we have lost about 60 or so plants with about as many
showing the early stages of the infection. It also seems to affect our
mid to largest size specimens rather than the smaller plants.
Has anybody seen this before? Any recommendations? I am going to try a
fungicide this week, but with the huge number of plants we have spread
out all over our 60+ acre gardens, I am worried about how effective
any methods will be in controlling this. If anyone is interested I can
email photos of affected plants in various stages of infection.
Thanks
Adam
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