Smithsonian Gardens Orchid Collection: Orchids get Sick Too
Orchids in our greenhouses aren’t immune to disease (unfortunately), and when virus symptoms appear, steps must be taken to remove any infected plant to prevent viruses from spreading and to preserve the overall health of the collection. Cymbidium mosaic virus and Odontoglossum ringspot virus are the most common orchid viruses, and symptoms include black spots on flowers, general discoloration, and decreased flower production. For orchid growers, these symptoms are a nightmare, since their job is to grow display worthy orchids with “wow” factor.
Rucha Shevade, a former collection intern, has been diligently virus testing numerous orchids in the collection for both viruses using the Agdia Orchid ImmunoStrip test. To test a plant, Rucha will crush a small piece of orchid tissue in a buffer solution to create a liquid test sample, and then insert an ImmunoStrip into the sample for 2-4 minutes. Each strip has a colored control line which must appear for the test to be valid, and a colored line for each of the viruses that are being tested for in the event they are positive. If a plant tests negative for both viruses, it is given a tag that is labeled “VIRUS FREE.” Ideally, every plant in the collection would receive a virus free tag, but many orchids have to be thrown out.
Luckily there are several ways to prevent and limit virus infection and transmission in the collection. Orchid curator Sarah Hedean is a stickler for “good culture,” which she says is the key to maintaining a healthy collection of beautiful plants. Good culture starts with choosing virus free plants. This means looking for symptoms and testing plant tissue for viruses before an orchid is even brought into the collection. The next step to good culture is to have high housekeeping standards, which can limit pest presence in the greenhouse. This includes things like having good air circulation, keeping benches and floors clean and removing dead leaves from plants. Finally, good culture involves limiting contact between plants, and ultimately limiting potential virus transmission. This means spacing plants evenly along benches, and disinfecting tools such as scissors after they have been used on a single orchid.
Check out the AOS page about orchid viruses and virus testing for more information.
Julie Rotramel, Orchids Intern