Identification and Management of Botrytis Blight

Botrytis Blight is a fungal disease that commonly affects both annual and perennial herbaceous plants. There are several species of Botrytis which cause blight, the most common being Botrytis Cinerea.

Botrytis Blight is commonly contracted in the spring and usually thrives in cool, damp weather. It is especially damaging after several days of rain. The disease can survive on crop stubble over the winter and then spread.

Commonly Affected Plants

Anemones, chrysanthemums, begonias, dahlias, geraniums, marigolds, pansies, petunias, roses and sunflowers are all susceptible to Botrytis Blight.

Fruit and vegetable plants that are susceptible the disease include beans, asparagus, carrots, grapes, lettuce, peppers, potatoes, raspberries, strawberries and tomatoes.

Botrytis Cinerea afflicts wine grapes, and Botrytis Fabae is often seen in faba bean plants.

Signs and Symptoms

Botrytis Blight is evidenced by brown spots on plant material. Botrytis Fabae, sometimes referred to as Chocolate Spot Disease, appears as reddish-brown spots on leaves, stems and flowers. It rapidly infects, grows and produces spores and thrives in warmer humid conditions.

Once “chocolate spots” appear on leaves, stems and flowers they enlarge and develop dead, gray centres. Botrytis Fabae can kill flowers and stems.

Botrytis Cinerea is a necrotrophic fungus that materializes as gray mold. Masses of gray spores may cling to dead or dying tissue. When the spores are liberated, they appear as dust coming off the plants. Occasionally, tiny black structures form later in the summer.

In wine grapes, Cinerea can result in two different infections; gray rot in humid conditions and noble rot when dry periods follow wet weather. Noble rot removes water from grapes, leaving a higher percentage of solids – sugars, fruit acids and minerals. Gray rot requires a wound from insects, wind or accidental damage in order to spread. The resulting bunch rot can cause major losses for the wine making industry.

Disease Management

Frequent inspection of at-risk crops and thorough sanitation are the two most important actions for controlling Botrytis, whether Cinerea or Fabae.

It is possible to prevent infection with blight by avoiding overhead watering, syringing and misting plants. Always promote rapid drying and leave a generous amount of space for air circulation.

If crops have been stricken with blight remove infected flowers, leaves or entire plants as necessary. Avoid removal when crops are wet as it can spread the spores.

Use of a fungicide spray such as OxiDate is highly recommended for both prevention and treatment. Apply it in spring when the weather is cool and wet, or if blight was a problem in the previous year.

Crop rotation and regular weeding are also important in the prevention and treatment of Botrytis.