"Mr Richard Thomson" <[EMAIL PROTECTED]> spaketh thusly: > Hi all, I am seeking a better understanding of some > aspects of virus that effect orchids. I understand that > the virus can remain as a protein type material in dead > plant tissue indefinitely. And also, perhaps in potting > media. And reactivates when it comes in contact with > plant material. > Perhaps my understandings are not correct.
I think you'd have to specify which virus or viruses concern you. Some plant viruses are remarkably stable; one strain of a tobacco tobamovirus demonstrated infectivity from pressed herbarium specimens that were 45 years old (Randles, Search 2: 30, 1971). On the other hand, cymbidium mosaic potexvirus live no more than 25 days without a host (Brunt, A.A., Crabtree, K., Dallwitz, M.J., Gibbs, A.J., Watson, L. and Zurcher, E.J. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 20th August 1996). But cymbidium ringspot tombusvirus can live as long as 300 days (ibid). There are no data on the LIV (longevity of infectivity) for odontoglossum ringspot tobamovirus, at least as I can find. Given the longevity of other tobamoviruses, it could be infective for years as the stability of this family of viruses is remarkable. Others are quite short-lived; vanilla necrosis potyvirus has an LIV of 1-2 days (ibid). Look at it this way: common cold viruses are relatively short-lived outside the host, with rhinoviruses lasting on the order of minutes. Hepatitis, on the other hand, can last 14 days on a clean, dry surface with nothing more than old back issues of "People" magazine to read. Given the number of viruses that infect orchids at least occasionally, and that at least some of these viruses are particularly long-lived in the absence of a living host, there are certain precautions that should be taken. I recommend burning your collection annually, and start with new plants at least once a year. Fire is strong medicine, but it cures all ills. Except maybe prions. Cheers, -AJHicks Chandler, AZ _______________________________________________ the OrchidGuide Digest (OGD) orchids@orchidguide.com http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
