Primarily Cymbidiums: June NCOS: Virus testing

An esteemed member of our club, Joe Francis, led a discussion at today's meeting on orchid viruses. Joe has an extensive collection of 1,500+ orchids, and began virus testing in early 2009. Presently, his data comprises about 760 tests from his own collection, from hobbyiest colleagues, and from demonstrations at the talks he's given at our regional sister orchid societies.

Joe brought in two demonstration Cattleyas: one showing virus-infection symptoms (CymMV/ORSV double positive) and one that had no visible blemishes (ORSV positive). The bottom line--you can't tell whether an orchid is virused just by looking at it.

I performed 11 on-site tests at today's meeting. Some members brought in leaf samples for testing, but I also asked those who brought in plants for the show table if I they would volunteer a plant to be tested.

Laelia purpurata var. carnea 'Lady Godiva', exhibited by Jeff Johnson. (tested clean)

With the Agdia test strips, Joe's data indicates an overall infection rate of 29%: 16% CymMV, 11% ORSV, and 2% CymMV/ORSV double positive. Presently, the overall Cymbidiums infection rate is 52%, and the overall Cattleya Alliance infection rate is 22%.

Joe then discussed cultural practices to reduce mechanical transmission of virus, e.g. using clean, sanitized and sterilized tools with each plant, using clean, fresh gloves when handling plants for re-potting, using a fresh layer of newspaper as a surface cover when re-potting orchids, cleaning the grow benches, and avoiding water drip from a first plant onto a second plant.

There was also a discussion of how one may clean plastic and clay pots for re-use. It quickly became clear that each person had his/her own way of cleaning pots prior to re-use. I also know of other growers who only use brand new pots. I can see the advantages of this latter strategy, but I haven't yet performed a cost/benefit analysis to decide which solution to practice. I really prefer to minimize the amount of trash I contribute to the landfill. But, if the plastic is recyclable and I can find a source of plastic pots for a reasonably cheap price, then I may switch over to this strategy altogether to eliminate a variable.

All in all, the members appreciated hearing about orchid viruses and how to avoid them. They also wanted to know how to access the testing kits. Joe provided the contact information, and our club will begin providing a testing service and/or virus testing workshops.

Cattleya Marjorie Hausermann 'York', AM/AOS, exhibited by Gene Schurg. The green lip is visible via camera flash, but appears white to my eyes.