Virus in Slipper Orchids by Bob Wellenstein

Is it true that orchid viruses do not infect Paphs?

        This is a common misconception. Paphs are capable of hosting virus infections. In the past we have isolated ORSV (Odontoglossum Ringspot Virus), CyMV (Cymbidium Mosaic Virus) and BYMV (Bean Yellow Mosaic Virus) from different clones, and there are other reports in the literature. What is true is that infection rates tend to be low, probably because Paphs are rarely divided by cutting with a sharp instrument, but are simply broken apart, or allowed to fall apart on their own. The only symptoms we have seen occasionally in those Paphs that were positive was a general unthriftiness in the plants that were infected with BYMV. Rates of virus infection in Phrags tend to be a bit higher than in Paphs, but still lower than with other commonly cultivated orchids. The most likely to be infected are the clones that have been around for a very long time and in mixed orchid collections, resulting in an increased chance of being exposed, again usually via cutting tools.

How can I tell if my plant is virused?

        You need to send a leaf sample to a laboratory that does plant virus testing, and even with testing you can only be reasonably sure it's okay for those viruses expressing epitopes the antibodies used in the assay were created against (assuming some sort of serologic assay is used, the most common type), or if it tests positive. The most commonly encountered viruses, and therefore those which are tested for most frequently, are CyMV, ORSV and BYMV. BYMV can be tested for using a Potyvirus specific monoclonal antibody, so this assay would potentially pick up any other Potyviruses present (several have been uncommonly isolated from orchids). If you suspect your plant is virused, but are unable to have it tested, it is advisable to place this plant where its run off water will not fall into another plant below it. If you handle the plant, do so as the last item on your days' agenda, and wash your hands thoroughly after handling it. If you need to pot this plant into a bigger pot, wash and then disinfect the old pot with a 10% Clorox bleach solution, or discard it. There is also some question about whether using pollen from virused plants onto uninfected plants will cause transmission of the virus; if you are in doubt about the quality of the pollen, find different pollen to use. Lastly, infected plants may show no symptoms whatsoever, and may grow and flower as well as uninfected plants, so always sterilize any cutting tools you use on your plants in between cuts. Never reuse old mix even if it looks fine, disinfect old pots before reuse, and don't allow runoff water to go from pot to pot. Control of sucking insects, particularly aphids, is also of utmost importance in minimizing risk of spread of viruses in a collection.

 
Bob & Lynn Wellenstein
AnTec Laboratory
PO Box 65
Candor, NY 13743 USA