ORCHID PESTS & DISEASES
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Healthy orchid plants are less likely to have problems with pests, fungal or bacterial infections or indeed viruses. Always ensure your plant receives the best care. Water, wherever possible, with rain water at the same temperature as your plant; feed regularly with a good quality orchid fertiliser supplied by an Orchid Nursery; re-pot at least every two years using a good quality compost supplied by an Orchid Nursery; maintain a good level of humidity as most pests are more active when the atmosphere is warm and dry and if you are growing plants in the home spray them every morning with tepid water and/or stand them on a tray of moisture retaining clay balls eg. Hydroleca. If you can, ensure there is good air movement around your plants as fungal problems are far less prevalent where there is a buoyant atmosphere.
The main pests you are likely to encounter are aphids, spider mites, scale insect and mealy bug.
Thin leaf plants such as Cymbidiums or Oncidium type can suffer from spider mites and aphids. You can check for spider mites by looking at the underside of the foliage which will appear to be silvery in colour as opposed to green. They are very small so difficult to see with the naked eye but a small magnifying glass will make these visible or a fine misting spray may show up their webs. Aphids are much more visible and familiar and secrete a sugary liquid which can turn into a black and unsightly fungus. You can treat bothspider mite and aphids by wiping the foliage with soapy water or special plant wipes, or spray with a systemic insecticide available from most Orchid Nurseries that sell accessories.
Fleshy leaf plants such as Phalaenopsis and Cattleyas can suffer from scale insects which can be either soft or hard shelled insects that are attached to the foliage or pseudobulbs. Mealy bug is a soft bodied insect which looks like a very small wood louse and usually is visible as a cotton wool like material on the underside of the leaf, stems, in the bracts or indeed in the compost. The best way to treat scale insect and mealy bugis by wiping the foliage with soapy water or special plants wipes, or spray with a systemic insecticide available from most Orchid Nurseries that sell accessories, much the same as with spider mites and aphids. If the extent of the mealy bug problem is small and localised you can use a paint brush or cotton bud soaked with some methylated spirits to wipe away the insect.
Most diseases are spread through insects so make sure your plant is pest free and when re-potting your plant always obtain your compost from an Orchid Nursery. You should always use new pots or clean old ones in a dilute solution of bleach and, if you use any cutting tools, make sure they as sterilised before and after use.
There are a number of diseases that affect orchids although in most cases the cause is as a result of unsatisfactory growing conditions. If you follow the guidance at the top of this page you should avoid most of the problems but if you are unfortunate to suffer any problems the removal of infected tissue may stop it from spreading. However, if your plant develops marks on the foliage and you do not know what they are you would be well advised to seek out an orchid expert (See the list of BOGA Members on pages 13 – 15) or join an orchid society near to you (See the list of Member Societies of the BOC on pages 3 – 7) to advise you and to ensure the plant is not suffering from a virus. In any case the plant should be segregated from any other orchids until the problem is identified and treated.
Information taken from the Growers and Buyers Guide to Orchids in the UK – (Golden Guide 2013)