I wondered about how we judge 'by sight' if a plant has a virus. I know about color break in a bloom. I know about a trapeziodal mark on a leaf of a cymbidium. I know about longitudinal streaks in a leaf.
Of these 3 the only one I believe to be pathognomonic is the trapezoidal mark on a cymbidium leaf. Color break can come from a variety of sources, heat, pesticides are two that come to mind. Streaked leaves from heat or other poor culture.
In the back of my mind I recall that old cut-flower houses didn't really care about virused plants as long as the virus didn't affect the bloom, therefore there are several viruses housed in orchids, but since they don't affect the blooms they aren't considered a problem. Also in the back of my mind I recall that labs only test for a few viruses and you have to know which is virus a problem for your plant; like should you care about odont ring spot or cymbidium virus if you only grow cattleyas? Which brings up another possible myth: not all orchids are 'susceptible' to virus (Paphs aren't?? something like that.)
Any information would be a help. Obviously I've got a lot to learn
K Barrett
N Calif, USA
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