Diagnosing

• Botrytis cinerea causes small black spots to appear on the flower of the white cattleya orchid. If the fungal infection is severe, these small black spots can merge to become large black areas. The plant will not die from the fungal infection, but the black spots detract from the beauty of the flower.
  
  

Causes

• Infection with Botrytis is caused by too much moisture on the plant. Excessive humidity or water on the petals and leaves of the plant create a moist environment in which fungi thrive. Having dead plant material around the plant can also cause conditions in which Botrytis can proliferate.
  
  

Effects

• Botrytis fungus itself will not kill the plant. However, any fungal infection can cause the resistance of the plant to decrease, increasing the likelihood that the plant will contract a more serious infection. The black spots caused by the Botrytis fungus can be more serious for other plants such as strawberries.
  
  

Treatment

• Remove the affected areas of the plant immediately. Track down the source of excess moisture. This may be a humidity level that is too high, a source of standing water near the plant or improper watering technique. Commercial fungicides will often kill the fungus, but once the discoloration has occurred it is too late to save the bloom. Altering the conditions of the plant to ensure optimum airflow is the most effective means of treating the plant.
  
  

Prevention

• The most important way to prevent Botrytis infection in your white cattleya orchids is to make sure that air flow around the plant is sufficient. Leaves should be completely dry by nightfall, and air should be allowed to flow around all parts of the plant to help ensure the plant dries out. Botrytis fungus thrives in moist conditions, so dry leaves will help arrest its development. Avoid watering the flowers or leaves directly; instead, water only the soil around the plant.