Thursday, May 31, 2012

Botrytis Blight in the Landscape

A couple of weeks ago, we told you that Botrytis blight was especially active in greenhouses around North Carolina. Botrytis blight is a common problem in greenhouses and can be very destructive if allowed to go unchecked. Now that the weather outdoors feels a lot like a greenhouse – warm and humid – Botrytis blight will be popping up in home landscapes everywhere. 
Botrytis blight (Photo: D. Shew)
Another name for this disease is gray mold, which perfectly describes the appearance of the pathogen, Botrytis cinerea. Most of you have probably witnessed gray fuzzy “whiskers” of Botrytis as it eats up strawberries left on the counter too long! This fungus can be particularly problematic after several days of rainy, drizzly weather or in shaded areas of dense vegetation and high humidity. Botrytis cinerea infects a wide range of ornamental hosts including petunias, pansies, geraniums, snapdragons, begonias, periwinkles, roses, and zinnia. Botrytis cinerea can also infect a variety of fruits and vegetables including beans, carrots, grapes, peppers, and tomatoes. Areas with dense plantings of bedding plants, like petunias or pansies, are good spots to find active Botrytis infections. 
Botrytis blight in bed (Photo: D. Shew)
Botrytis usually infects tender tissue like flower petals, buds, and seedlings, damaged tissue, and dying or aging tissue. Infections begin as small tan to brown spots. Over time, prolific gray spore masses are produced on dying tissue. In severe cases, Botrytis infections can cause stem cankers or even kill plants. 
Botrytis blight: Early symptoms (Photo: D. Shew)
Botrytis blight on dogwood (Photo: D. Shew)
Botrytis stem canker (Photo: D. Shew)
The best way to control Botrytis blight in the home landscape is sanitation. Inspect plants regularly and deadhead spent flowers. Be sure to carry a paper bag with you to avoid dusting spores to healthy plants. Clip or prune cankers and remove plants with severe infections. Avoid picking off infected tissue when plants are moist so you don’t spread spores around during optimal infection conditions.
Strawberry loaded with Botrytis spores (Photo: Meagan Iott)