Botrytis Blight or Gray Mold

Problem type: Disease

Name of problem: Botrytis blight or gray mold

Plant name(s): House plant hosts include African violet, rubber plant, pothos, dracaena, philodendron, ferns and palms

Symptoms / Characteristics:
Infected tissues initially exhibit gray-brown, water-soaked lesions that blacken with age. A fuzzy, grayish mold develops on the surface of infected blossoms and leaves. Infected buds may blacken and rot and sunken cankers may form on infected stems. Stem and crown rot may also occur. Round, black fungal bodies are often visible on dead tissue. Botrytis blight fungi will attack almost any plant organ, though tender or weak tissues tend to be most susceptible. Leaf and blossom blight are the most common symptoms of the disease.

There are many species of Botrytis fungi with a vast collective host range. These devastating fungi are known to attack an array of house plants, bulbs, woody and herbaceous ornamentals, fruits and vegetables. Botrytis cinerea is perhaps the most destructive species. Prolonged periods of cool, moist conditions facilitate the development and spread of Botrytis blight.

Control / Preventions:

The immediate removal and disposal of infected tissues may not necessarily eradicate the disease but will effectively slow its spread. Infected plants should be completely isolated until an appropriate control has been administered. The plants must not be returned to their original location until symptom development has ceased.

Because high moisture facilitates the development and spread of the disease, it is a good idea to water plants at the soil surface instead of overhead. Overhead watering promotes leaf wetness thus aiding in the creation of a high moisture microclimate ideal for Botrytis fungi. Allow the soil to dry slightly between waterings. Ensuring adequate spacing between plants/pots will also improve air circulation and promote leaf dryness.

If chemical control is warranted, use a fungicide that is registered for controlling Botrytis blight in house plants. Botrytis blight is easily prevented by employing proper sanitation and effective cultural practices. Remember that the fungi tend to thrive on weakened or injured tissue. For African violets and other flowering house plants, remove spent flowers on a regular basis, as these senesced tissues make an ideal host for Botrytis fungi. Keep the plants as healthy and vigorous as possible by implementing a balanced fertilizer program and an effective watering plan. Avoid any unnecessary stress and injury that might render a plant particularly susceptible to Botrytis fungi.