Botrytis Blight in Vegetable Greenhouse and Plant Beds
Plant Pathology Information Note 118 (PPIN-118)
Charles W Averre, Extension Plant Pathologist
Botrytis blight is caused by a fungus (Botrytis cinerea) that attacks many succulent plants. In most years it causes considerable damage in a few operations to seedlings in plant beds and producing tomatoes in greenhouses. This disease usually affects plants at the tip of the younger leaves, causing a water-soaked area. The infected areas of the leaves enlarge and the fungus appears to grow down the leaf petiole into the main stem. The diseased area becomes covered with a fluffy, brownish-gray mold. The disease has not been observed as a problem in the field in Eastern North Carolina. On producing tomatoes it causes foliar blight, stem rot, and fruit spotting and rot.
Botrytis blight is associated with excessive moisture and high humidity as a result of poor ventilation in covered plant beds and greenhouses. Growers are urged to take every precaution to provide adequate and continuous ventilation, especially during periods of cool, cloudy and wet weather. Most growers are able to avoid serious Botrytis blight problems without the use of fungicides by keeping humidity low in the structure. Specific steps include: (1) wider plant spacing, (2) continuous introduction of some cold air when house is closed, (3) continuous forced air movement with fans when house is closed, (4) use of "speeding trays" in racks above ground or placed on rocks or plastic ground sheets on the ground, (5) good soil drainage, (6) covering ground with plastic sheets, and (7) not using sprinkler irrigation.
There are few registered fungicides for use in covered plant beds and greenhouses. Fungicides must be used with caution in order to avoid health hazards during application, illegal residues on commodities, and buildup of Botrytis resistance to the fungicide. Be sure to read the label carefully, and be sure that the fungicide selected is registered for the intended crop.
occasionally used to control Botrytis blight on vegetables in covered
plant beds and greenhouses. Read the label carefully and be sure the fungicides
is labeled for the specific, intended crop. Follow all precautions on
North Carolina Cooperative Extension Service
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of specific chemicals are based upon information on the manufacturer's
label and performance in a limited number of trials. Because environmental
conditions and methods of application by growers may vary widely, performance
of the chemical will not always conform to the safety and pest control
standards indicated by experimental data. All recommendations for pesticide
use were legal at the time of publication, but the status of registration
and use patterns are subject to change by actions of state and federal
regulatory agencies. Last printed 02/91