Writing from experience, I can say that many new growers have nasty experiences with orchid viruses in their early years. If the orchid ‘bug’ strikes them hard, they race around collecting cymbidiums willy-nilly, regardless of their source (family ‘heirlooms’ are worst). These plants often harbour a variety of pests and diseases, such as scale, red spider and, most serious of all (because they are incurable), viral infections. Virus-infected plants provide a source from which healthy plants may become infected unwittingly during re-potting and handling. Here are a few tips that can minimise the spread of pests and diseases throughout your collection.

When buying (or accepting gifts of) new orchids, look for strange leaf markings, particularly yellow streaks and small black patches of dead tissue, which are signs of virus infection. If in doubt, don’t buy, regardless of the price.

Having made your purchase, before adding the plant to your collection spray it with an insecticide to ensure that it doesn’t carry any hidden pests. You may also wish to spray the foliage with white oil (also known as summer oil) to kill any red spider present – heavy infestations reveal themselves as a whitish network on the under-side of the leaves. Please note, though, that white oil should not be used in hot weather, and that it may damage plants with thin, tender leaves (e.g. lycastes) at any time.

If you are one of the lucky ones with lots of bench space, set your new acquisitions apart from your other orchids for a few months, until you are sure that the new plants are quite healthy. The same applies to any suspect plants in your collection – set them apart until you receive advice from an experienced grower that your fears are groundless. If he or she confirms that your plant probably has a virus infection, dispose of it – don’t leave it around as a future source of infection.

To minimise the spread of virus, treat every plant in your collection as if it is infected with virus. When cutting old flower spikes or trimming damaged leaves etc., use sterile knives or scissors, and sterilise them again before using them on another plant. I have a set of eight pairs of stainless-steel scissors that I use on my orchids. After use I wash them along with our kitchen dishes, and then heat the blades to red heat over a gas flame; take care not to overdo it, or the plastic handles will melt! By having eight pairs of scissors I can handle eight orchids before I need to sterilise my scissors again. When dividing cymbidiums I use old stainless steel kitchen knives, sterilising them in the same way. As a further precaution it’s a good idea to wash your hands in hot soapy water after handling each plant.

A few other precautions to take when re-potting are:
• don’t re-use pots unless you have washed them well in hot soapy water and then sterilised them by soaking in strong Tricleanium® (trisodium phosphate) solution overnight – be warned that this solution is highly alkaline, so you should wear eye protection and rubber gloves.

• never re-use potting mix, which may carry virus-infected material.

• don’t re-use old stakes (some growers reverse them end for end and use them for a second season).