Diseases
Botrytis - greenhouse tomato
Petiole stems on greenhouse tomatoes may become infected with Botrytis blight. As the disease progresses, main stems can become infected so that the plants may be girdled and die. The fuzzy grayish-brown spores, seen in this photo, are easily spread on air currents and by water splash.
Botrytis leaf spot, stem canker, blight, and ghost spot is caused by Botrytis cinera. This pathogen is very important on greenhouse tomatoes or hydroponic systems. This pathogen is ubiquitous in the environment, has an extremely wide host range, and prefers to attack senescent and/or injured tissue. Botrytis can be controlled by management of environmental conditions, sound cultural practices, and fungicide applications. Control weeds and remove plant debris. Space plants to allow good air circulation, reduce humidity within the canopy, and minimize leaf wetness. Improve horizontal air flow with fans. Reduce humidity by a combination of heating and venting in the evening, particularly when warm days are followed by cool nights. Water in the morning if practical. Fungicides appropriate for Botrytis include 26 GT, 26/36, Compass, Cleary's 3336, Botran, Decree, Daconil, Dithane, Heritage, Exotherm Termil, Sextant, Protect DF, and Medallion. Check label for host appropriateness. Resistance to Cleary's 3336, 26 GT, and Sextant has been reported in Botrytis populations. Always alternate fungicide applications between materials with different modes of action to prevent resistance development.
Fact Sheet: Botrytis Diseases of Greenhouse Crops
Fact Sheet: Reducing Humidity in the Greenhouse
For more information about Botrytis see: New England Recommendation Guide
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