Key points
- The blight fungus Botrytis species attacks plants in landscapes, especially under cool, wet, overcast, or very humid conditions, which cause plant parts to remain wet for extended periods.
- In all species of Botrytis, the first symptom is a small tan spot or spots that may rapidly enlarge.
- If the stem is infected, girdling the stem, the shoot will wilt.
- Botrytis is easily diagnosed by the fluffy gray mold produced on blighted plant parts under moist conditions. Botrytis can rapidly blight flowers.
- Infected petals that fall onto foliage or stems can cause additional blighting and dieback.
Other species of the Botrytis fungus are specialized to attack a more narrow range of plants. B. elliptica attacks lilies, causing leaf spotting that progresses up the plant, blighting leaves, stems and flowers. B. paeoniae causes bud and shoot blight of herbaceous and tree peonies. B. tulipae causes the disease "tulip fire," characterized by a rapid spotting and blighting of tulip petals and foliage.
Management
- Prevention of Botrytis diseases can be very difficult when the weather conditions are overcast, cool and very moist.
- The basis for control is sanitation and prevention of extended periods of leaf wetness.
- Remove blighted plant parts from the garden.
- Space plants to allow rapid drying after rains or irrigation. Avoid overhead irrigation and water early in the day.
- The cornerstone for control of all blight diseases is sanitation both during the growing season and in the fall.
- Wilted and blighted plants and plant parts should be promptly removed from the garden.
- In the fall, all plant debris should routinely be cut at ground level and removed. This material may be composted.
Rev. 2020