Gray-mold rot or Botrytis blight, caused by the widespread fungus Botrytis cinerea, affects most vegetable and fruit crops, as well as a large number of shrubs, trees, flowers, and weeds.
RPD No. 942 May 2000
DEPARTMENT OF CROP SCIENCES
UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
GRAY-MOLD ROT OR BOTRYTIS BLIGHT OF VEGETABLES
The disease is favored by coolmoist conditions and little or no wind. Cool, damp, poorly ventilated greenhouses are ideal for the disease, and Botrytis blights are probably the most common diseases of greenhouse-grown crops, especially in the spring and fall when the vents of greenhouses are closed at night to prevent heat loss. In the greenhouse, gray mold is Figure 1. Botrytis fruit rot of pepper. Note the typical often saidto be a disease of bad management. Gray- dense gray mold on the decayed area (courtesy Dr. A.O. mold losses in the field are severe following Paulus). prolonged periods of overcast skies, fogs, heavy dews, or light drizzly rains. The fungus causes primarily blossom blights and fruit rots, but can also cause damping-off, bud rot, stem cankers or rots, leaf spots or blights, bulb rots, and tuber orroot rots. Botrytis is also a problem on fruits and vegetables in cold storage and subsequent shipment because the fungus is able to function at temperatures just above freezing. With some possible exceptions, Botrytis mainly attacks tender tissues (flower petals, buds, or seedlings), weakened or injured tissues, and aging (senescent) and dead tissues. Actively growing tissues, other than flowerpetals, are seldom invaded directly.
Symptoms of Botrytis diseases vary greatly depending on the host and plant part attacked. Generalized symptoms include a gray to brown discoloration, water soaking, and a fuzzy whitish gray to tan mold (mycelium and spores) growing on the surface of affected areas.
Blossom Blights and Fruit Rots
Blossom blights often precede and lead to fruit andstem rots. Aging flower petals of beans, carrot, celery, eggplant, onion, pepper, squash, and tomato are particularly susceptible to colonization by Botrytis species, and under cool, humid conditions abundant mycelium and conidia (spores) are produced on colonized petals. The fungus often grows from the fading flower petals into the rest of the inflorescence,
Further information on vegetablediseases can be obtained by contacting Mohammad Babadoost, Extension Specialist in Plant Pathology, Vegetable and Fruit Diseases, Department of Crop Sciences, University of Illinois, Urbana-Champaign.
University of Illinois Extension provides equal opportunities in programs and employment.
-2or into developing fruit where it causes a blossom-end rot. From there it can spread and destroy part orall of the fruit. Fruit can also be infected by conidia entering through growth cracks, cuts, stem scars, insect wounds, or lesions made by other pathogens. Infected fruit develop watersoaked, yellowish green or grayish brown irregular lesions which can be somewhat soft and spongy in texture. When conditions are favorable, mycelium and conidia are produced on the lesion surface. The fungus caninfect the Figure 2. Gray mold lesions on the pods of snap fruit of cucumber; squash; eggplant; pepper (Figure 1); snap (Figure 2), kidney, and Lima beans; lentils; and beans. tomato (Figure 3) to name a few.
Leaf and Head Rots
Botrytis leaf infections can develop on some crops. Leaf symptoms first appear as small, soft, yellowish or tan spots. Later the spots become whitish gray or tan, and mayenlarge and coalesce to the point where they can involve the entire leaf. Lettuce (Figure 4), escarole, endive, onion, and cabbage may be damaged severely. Botrytis first infects the lower, older leaves, often those in contact with the soil. Diseased areas become yellow and support a heavy growth of gray mold. Under cool, moist conditions, lettuce heads may be covered with fuzzy gray Figure 3....