Botrytis Blight
Friday, 08 April 2011 13:45
When weather is cloudy and cold for extended periods of time, be sure to monitor plants for Botrytis which can cause leaf and flower blight, cankers, damping off and root rot. Manage the greenhouse environment to reduce humidity, make sure plants are adequately spaced to allow for good air circulation and remove dead flowers as an infection source. Some growers are hanging fish netting under flowering hanging baskets to collect spent blooms, keeping them from susceptible crops below.
Apply preventative fungicides before cutting back plants so the fungal spores are not released onto open wounds as workers handle plants. On ornamental crops, a number of fungicides are labeled for use against Botrytis blight including Decree (fenhexamid), Daconil (chlorothalonil) Chipco, 26 GT (iprodione) and Protect T/O (mancozeb). Growers often rely on fenhexamid (Decree) which is a non-systemic fungicide with both protective and curative activity. Rotate among mode of action groups to delay the buildup of resistant strains. Decree (fenhexamid) resistant Botrytis were recently found in Pennsylvania greenhouses. See related message.
Basil and other tender herbs are especially susceptible to Botrytis Blight. On Basil, you will often see Botrytis Stem Canker. Botrytis lesions on the leaves lead to tan, stem cankers. See “Herb Bedding Plants Grown in Greenhouses” - for a listing of selected insecticides and fungicides labeled for use on herbs grown in the greenhouse.
Some preventive biological fungicides labeled for use on herbs include Cease, Companion, Mycostop, Actinovate (suppression). Some contact fungicides include Milstop (suppression) and Oxidate. Decree is labeled for cilantro, and leafy greens including chervil and parsley.
Photos
Botrytis (Fuschia stem cankers)
Fact Sheet
Botryis Blight on Greenhouse Crops
Leanne Pundt, University of Connecticut
Tina Smith, University of Massachusetts
