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The fungus that causes botrytis gray mold, Botrytis cinerea, invades weak and damaged plant tissue. Flowers are very susceptible during bloom, while berries are attacked at all stages of development. Gray mold spores survive in plant debris and are spread through the air during the whole growing season. Spores may also spread by splashing water or contact with infected plant parts. Cool temperatures, high humidity, and standing water on plants favor the disease, as do close plant spacing and overhead watering. Gray mold is more severe if crops are not rotated.
TARGET: Flowers, vegetables, and fruits, including peony, blueberry, grape, strawberry, bean, ageratum, begonia, dogwood, Gerbera daisy, geranium, and zinnia.
SYMPTOMS: Water-soaked lesions appear on leaves, stems, blossoms, or fruit. In advanced stages of the disease, lesions may be covered with gray spore masses. On peonies young flower buds turn black and wither; older buds turn soft and brown; and stems wilt and die.
PREVENTION Create good air circulation by spacing plants properly. If possible, orient crop plants in the same direction as the prevailing winds. Mulch with pine needles, straw, or plastic to keep fruit off the ground. Harvest small fruits every few days when ripe. remove faded flowers from annuals and perennials.
CONTROL: remove and discard all dead or infected plant parts. to control gray mold on peonies, spray with mancozeb. For grapes, strawberries, and other fruits, use captan. for annuals and perennials, apply chlorothalonil (Daconil). Apply all fungicides according to label directions.
References:
1. Garden Problem Solver by Steve Bender
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