It's possible to become very philosophical about virus testing in
orchids. There isn't a lot of good literature on them, a lot of bad
literature, and a bunch of stuff that nobody can (or wants to) believe.
It's a minefield.

Visual tests: The ol' EBT (eyeball test) doesn't measure up.
"Looks like virus" flat-out doesn't cut it.

Lab tests: The standard ELISA test has some problems to it. The
first thing is that orchids *may* have a propensity to give false
positives (as related to me by a PhD in plant pathology from a leading
school). The other problem is that there are a number of viruses that
afflict orchids, and the big two are the only ones people test for.
ImmunoStrips may be better, or may not. Agdia now sells twin tests for
CyMV and ORSV- two tests on one strip. The price drops to $5/test in
quantity.

The only test that seems to meet the criterion for low false
positive, low false negatives, detection of multiple viruses- and has the
benefit of being inexpensive- is the ol' indicator plant. Plants are grown
from seed, the leaves are scarred with some sandpaper, and plant juice is
dripped into the wound. Some indicator plants fail to undergo systemic
infection, meaning multiple leaves can be tested and "read." It also may
be useful for some (not all) viruses that we normally don't test for-
impatiens necrotic spot virus (INSV), turnip mosaic potyvirus, orchid
fleck rabdovirus, vanilla mosaic potyvirus, etc.

Northen's "Home Orchid Growing" has a good section on use of
indicator plants. I understand some species of Oxalis are useful, as is
Cassia occidentalis. I also understand some cultivars of what used to be
very useful indicator plants have been selectively bred for their
*resistance* to viruses, so when possible wild strains should be selected.

The address in the header is not valid. Send no email there.

-AJHicks
Chandler, AZ