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

From: Adam Black epiphyte1 at earthlink.net> on 2006.07.17 at 06:23:15(14431) 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 +More 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 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" 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 _______________________________________________ Aroid-l mailing list Aroid-l@gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l _______________________________________________ Aroid-l mailing list Aroid-l@gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l 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 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! 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