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Re: [Aroid-l] - Serious spreading Amorph disease-Collar rot

  • Subject: Re: [Aroid-l] - Serious spreading Amorph disease-Collar rot
  • From: bonaventure@optonline.net
  • Date: Sat, 22 Jul 2006 21:59:40 -0400
  • Content-language: en
  • Priority: normal

Adam,

Do you mean you grow your paeoniifolius in the ground outdoors? What hardiness zone are you? I pot mine and bring them inside in late October before our first expected frost, along with mossambicensis, and immature lewelii and henryii, and Taccarum wendelianum, and now also Amorph. bulbifer, which I almost lost completely. They then are not watered until May, and the petioles undergo a long and gruesome collapse and drying off before they can be plucked off. Only my konjacs, yunnanensis, dunnii, and of course Typhonium venosum winter over outdoors and are permanently planted in the soil.

Bonaventure Magrys

Cliffwood Beach, NJ USA zone 7

 

Hi everybody,

I am a little late in thanking eveyone for their input on our diseased Amorphophallus. Seemed like the consensus was either an Erwinia bacterial infection or Sclerotium (Collar Rot) fungal infection, the latter suggested by Dr. Misra and detailed in his excellent article in Aroideana vol 26. The symptoms on our plants seem to match the Sclerotium more closely.

To those of you that requested photos of the infected plants,  I had planned to do so, but after my original posting to the list on this subject, I went back to work and could not find a single plant infected, and still have yet to see any more diseased plants. I am hopeful it has run its course. The symptoms appeared as we began receiving more regular rains after being in drought conditions for months here in north Florida, which correspond to Dr. Misra's description of changing environmental factors causing these outbreaks.

Though we weren't keeping track of numbers of casualties, our A. konjacs were hit the hardest, followed by A. bulbifer, but none of our A. paeoniifolius showed any symptoms. I had mentioned that most of our A. paeoniifolius were showing early signs of the disease, but upon closer examination, I figured out that the lawn service that maintains the grassy areas of the gardens had gone through with a weed-eater and trimmed the grass growing at the base of the petioles, whipping gashes in the base of the petioles. These injuries don't seem to be getting infected, and hopefully since the supposed Sclerotium outbreak has settled down, we won't see any more, for now at least. I still plan do do a soil drench with a systemic fungicide as Dr. Misra recommended just in case. And I have explained to the lawn service to keep their weed eaters away from the "giant celery lookin' things" as they called them.

Thanks again for everyone's help in this matter.

Adam

rajshekhar misra wrote:
Dear Adams,
The symptoms described by you are typical symptoms of
Collar rot disease of Amorphophallus caused by
Sclerotium rolfsii. We frequently observe this disease
in India. The Fungus is seed borne and also soil
borne. You might have seen white fungal mycelial
growth and mustard like structures called Sclerotia on
the infected surface. You can use systemic fungicides
like Carbendazim (0.1%) as soil drench to prevent the
disease.
For details, kindly go through my article in Aroideana
vol.26 on Field and Storage diseases of
Amorphophallus.
Sincerely
RSMisra

--- Peter Matthews <pjm@gol.com> wrote:

  
Dear Adam,

Did your garden recenty import Amorphophallus
specimens from SE Asia or
other places where the genus is native? If you could
identify possible
geographical sources, this might help narrow down
the search for a cause.

Also, I wonder if there are any insects that lay
their eggs in the lower
petiole area? In theory, a newly spreading insect
might spread a new or
existing fungus. I do not know of such happening in
Araceae, but it is
conceivable. Taro has taro-specific planthoppers
(Delphacidae) that lay
eggs in the lower petiole, and they are spread with
planting materials
when the petioles are kept attached to the corm.
There might be
planthoppers that are specific to Amorphophallus
(this is speculation).

If  you want, I could try to contacting konyakku
researchers here in
Japan. There would certainly be interested in the
outbreak you describe,
even if it is something new for them. Or they might
immediately
recognise what is happening to your plants. There is
a lot of experience
with intensive production of Amorphophallus here in
Japan.

Good luck...

Peter Matthews



On 8/7/2006, "Adam Black" <epiphyte1@earthlink.net>
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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Dr.Raj Shekhar Misra
Principal Scientist & Head 
Crop Protection Division
Central Tuber Crops Research Institute
Sreekariyam, Trivandrum-695017(India)
Mobile Phone No. 91-9446557657
Fax-0471-2590063
Phone-0471-2598551 to 2598554

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