Answer: There is a fungal disease called botrytis that causes brown spots on the leaves of African violets. High humidity, inadequate light levels, and poor air circulation contribute to the development of the disease. The best way to control it is to improve growing conditions and avoid overhead watering. Space plants so that the leaves of adjacent plants are not touching to minimize spread of the disease. Also, keep a close eye out for mites, because mite injuries are a common site for the fungus to enter the plant. Note that African violets are also very susceptible to root and crown rots, especially if they are overwatered.
There are several pests that regularly attack African violets in addition to mites, including thrips and mealybugs. Examine the plant frequently, checking the undersides of leaves for bumps or spots or webbing. Look also on the stems and in the crown of the plant.
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