Orchid diseases are usually caused by poor culture (no, not ballet) and growing environment. The best way to tackle orchid diseases is to prevent them in the first place by providing a clean environment with good watering practices and good air movement. However, just like humans, prevention does not always work and they do get sick once in a while. Since orchids cannot tell you that they are feeling sick, you will need to check on them before the diseases become incurable.
Types of Diseases
Orchid diseases can be fungal, bacterial or viral. The common fungal diseases you see on your orchids are sooty mold, petal blight, rust and black rot. They are usually caused by high humidity without sufficient air movement. Insects and pests also spread the fungus. The honeydew produced by aphids also promotes fungus growth.
Bacterial diseases like brown rot are usually caused by being too cold and/or too humid. The bacteria can also be carried by insects or pests crawling from an infected plant to another plant. The bacteria easily contaminate healthy plant tissues, pots, potting material, clothes and other supplies.
If your orchid plant has virus, you should immediately throw it out. (Burn it, quick!) Viruses are spread by pests or infected tissues of another plant. Even though they are usually not fatal immediately, they are pretty much incurable. Your poor plant will just get weaker and weaker over time, and the flowers might be deformed. Not pulling the plug on your diseased plant could mean spreading the virus to your entire collection.
Use of Chemicals
Growers usually use chemicals to treat fungal and bacterial diseases. Common fungicides and bactericides are Physan 20, Phyton 27, Diconal, Thioml. You might be able to find some in your local hardware store, or you can find them online. Fungicides and bactericides can be lethal to people and pets if they are not used correctly. Here are some tips for you:
- Don't put any in your coffee. Trust me on this one.
- Follow manufacturers' instructions. Don't use more than directed; not only is more not better, it might even be harmful to you and your plant.
- Test the chemicals on just one plant first.
- Make sure the chemicals are suitable for orchids. They should also be safe for indoor and greenhouse use.
- Don't mix two or more chemicals together.
- Keep the chemicals and the treated plants away from pets, children and food. It may take weeks for the treated plant to be safe again.
- Wear gloves and protective gear when you apply the chemicals.
General cleanliness of the growing area is extremely important to prevent diseases. Clear plant debris and make sure the area is not constantly wet. It's not a bad idea to use a one-percent bleach solution to clean the growing area periodically. Some people like to “rescue” less-than-healthy looking plant from nurseries. Well, don't. Buy healthy-looking plants and be absolutely sure they are disease-free before bringing them to your regular growing area.