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Winterview Orchids & Supplies Asian Cymbidium Orchids, traditional Chinese, Korean and Japanese Orchid Containers View Favorites | Home Page | Search Page | View Cart | Checkout |
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Root Rot |
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Root Rot Root rot is actually a disease caused by bacteria that thrive in high temperature and high humidity. The most common contributions to the disease are water logging of the media, compacted media with poor ventilation, higher acidity of decomposed media, and too strong fertilizer. Once root rot has set in the tips of the leaves will turn yellow and eventually the plant will perish for lack of nutrients. If detected early enough the condition can be reversed. The pot needs to be sanitized or changed, dump all of the media, cut off the rotted roots and leaves and dip the whole Cymbidium in the solution of 1% of potassium permanganate for about 15 minutes. And then take the plant out, wash it clean and dry it (overnight), the plant can be dipped into a greenhouse disinfectant like RD-20 as a second treatment (dilute it to instructions). The plant should be reset in fresh media and moved to a place that has high humidity and good ventilation. Avoid watering the plant for three to four weeks, while new roots begin to form. Recovery is gradual, and during this period fertilizer should be cut back severely. Resume the watering program cautiously and in moderation. Virus Asian Cymbidiums are susceptible to more than 10 types of known virus. The most common are Cymbidium mosaic virus (CMV) and the Ring Spot Virus. CMV looks like a mottled pattern that appears light green or yellow when viewed from the top of the leave, and seems to block the light and look like a darker shadow from the underside of the leaf. Ring spot virus appears as a yellow or black depression in the leaf. The ring size may grow over time. Viruses have no known cure. They are often regarded as a form of cancer of the plant. They will only get worse and may consume the entire plant turning it black. Increasing fertilizer will typically increase the rate that the virus spreads and manifests itself. If you suspect a plant of carrying a virus isolate it immediately. (Virus' are spread by insect vectors, human vectors and can even be spread by the plants rubbing against each other). Typically the virus will be worse in new growths. If the disease does not reverse then discard them. Throwaway or burn infected plants. The media or pots should also be disposed and thoroughly disinfect all tools used. Sunburn When Cymbidium is exposed to strong sunlight in summer, some chloroplast within the leaf tissues is damaged. Bacteria invade the weakened spot on the leaf, causing a black or dark brown spot. This is recognizable from other diseases because it is not accompanied by a depression on the surface of the leaf. While the damage will remain on the leaves that have been affected. Further damage can be avoided by increasing the shading, particularly avoiding the midday sun. Yellowing of Leaves Back bulbs or old growth are susceptible to their leaves turning yellow or browning at the tip. This may not be a result of disease or virus. Instead it may be the physiology of the plant. Make sure that you are not over watering, check fertilizer strengths and application frequency increase humidity in the space and maintain ventilation. Yellowing of Leaves Back bulbs or old growth are susceptible to their leaves turning yellow or browning at the tip. This may not be a result of disease or virus. Instead it may be the physiology of the plant. Make sure that you are not over watering, check fertilizer strengths and application frequency increase humidity in the space and maintain ventilation. This two-part article appeared in the American Orchid Society Magazine "Orchids" in July 1999 and August 1999. All photographs are copyright of Charles Marden Fitch 1999 and cannot be used without permission of him or the author. |
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