What to Do When an Orchid Gets Soft Rot? Causes and Control Methods

After an orchid contracts soft rot, water-soaked round or oval dirty-white small spots appear in the early stage. Within one or two days the lesions expand rapidly and turn brown; at this point the leaf surface loses its luster and becomes slightly wrinkled, and the diseased tissue is slightly sunken. Water-soaked areas or wounds rot very quickly. The lesions are mostly at the base of new shoots; once rotted, the shoots can be easily pulled up, or break off and topple over. A yellow-brown sticky fluid oozes from the diseased part, accompanied by a foul odor. This seriously harms the growth and development of the orchid.

Causes of Orchid Soft Rot

1. The garden soil used for growing orchids was not sterilized, or pond mud was used directly;

2. Water contaminated with bacteria from lake water was used for watering;

3. Excessive nitrogen fertilizer applied during the new shoot growth period makes the leaves grow plump and tender with a dark green color, making them highly susceptible to bacterial invasion;

4. The potting soil stays overly wet for a long time, so bacteria in the soil multiply in large numbers and produce toxic gases and substances, which lowers the plant's resistance and ultimately triggers soft rot.

Control Methods for Orchid Soft Rot

1. The garden soil and pond mud used for cultivating orchids must be exposed to high temperature in the sun and treated with a fungicide for disinfection, first ensuring that the soil contains no pathogenic bacteria;

2. Liquid nitrogen fertilizer should be applied from before the new shoots sprout until the new shoots have emerged but have not yet unfolded their leaves. Applying additional phosphorus and potassium fertilizer helps the leaves strengthen their disease resistance.

3. Diseased leaves found should be removed promptly and either burned in a centralized manner or buried deep to prevent re-infection, and care should be taken not to cause artificial mechanical damage, so as to prevent bacteria from entering.

4. It is best to choose water with a temperature close to that of the soil for watering, and the water used should be clean. When watering, do not pour water directly into the new shoots or the heart leaves.

5. In the early stage of the disease, a 160-fold Bordeaux mixture spray can be used for protection, spraying once every 5-6 days; spraying two or three times in succession gives better results. During seasons when the disease is prevalent, frequently use a 4000-fold solution of new plantmycin or agricultural streptomycin for control, once every 5-7 days, spraying two or three times in succession.