Asian Cymbidium Orchids, traditional Chinese, Korean and Japanese Orchid Containers

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Prevention and Control of Plant Diseases and Elimination of Pests

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Cymbidium Sinense Ta Ming, "Bright Light" shows its deep red flowers during the Chinese New Year in February.

Prevention and Control of Plant Diseases and Elimination of Pests

I come from the school that hates to use chemical insecticides unless absolutely necessary. Serious growers and collectors need to practice good growing practices to eliminate potential problems before they cause damage to the plants. Keeping the greenhouse or growing area clean and free of spend media, old leaves, and sick plants is key to maintaining a good environment. Healthy plants are much less prone to insects and diseases. In the case of Asian Cymbidiums, the pots can be hung from racks to maintain better ventilation around the bottom of the pot, and reduce chances of insect infestation in the bottom of the pot.

Plant Diseases

Anthracnose

Symptoms include the appearance of disease spots with oval shapes on the surfaces of leaves. The spots will grow from small to large and from yellow to black. At the worst case, the whole leaves will turn black. This disease is caused by high humidity with lack of air circulation. It spreads by spores and easily infects other leaves nearby. To control and eliminate this disease, clean up any debris or spent leaves, increase ventilation and avoid misting water directly onto leaves. Plants can be treated with Zyban or Chloroneb, follow directions carefully for proper dilutions. Repeat the process every 10-15 days for at least 2-3 applications. Symptoms should disappear. Remember damaged leaves on Asian Cymbidiums do not grow away.

Brown Spotting in Fresh Blooms

In China they call It Brown Spot Bacteria, but is probably Boyteritus. It often happens between April and May. When bacteria are brought into the young buds by rainwater and small spots like water stains appear inside the buds and turn from yellow brown to black. The buds will smell and turn brown. When the disease is found, the plants need to be move to places with more ventilation and less humidity. A fungicide, such as Zyban with zinc at a 600 dilution should be applied three times, with 10-15 days between applications. Use of RD-20 as a general disinfectant can help prevent brown spotting, by keeping the background levels of bacteria low.

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.