| Gray mold of strawberries is caused by a fungus,
Botrytis cinerea, which infects both the flowers and
fruits. Because of this, Botrytis can greatly reduce
fruit yields and is considered one of the most
damaging diseases of strawberry. Botrytis is most
prevalent during prolonged cool, wet weather
during bloom and near harvest.
Symptoms and Diagnosis
Blossoms commonly turn brown and die. A soft,
light brown rot may appear on any part of the berry,
but generally occurs first in the area of the cap,
destroying the berry within 48 hours. The infected
fruit spot is at first a light brown color and
somewhat soft in texture. As the entire berry
becomes infected, the rotted area becomes firm and
turns a darker brown color. Fruits soon "mummify"
and, like the blossoms, become covered with a gray,
dusty powder which are the spores of the Botrytis
fungus. Berries resting on damp soil or touching
infected plant parts are most commonly infected.
Life Cycle
Botrytis fungi overwinter as dark-colored, resting
bodies (sclerotia) on dead tissue. In the spring
during cool humid weather, spores form and spread
by wind or water to wounded or extremely soft plant
tissues. Infection can also occur from growth of
fungal mycelium from previously infected plant
parts. The fungus can survive on decaying vegetation
so it can infect healthy plants throughout the
growing season.
Integrated Pest Management Strategies
1. Remove infected plant parts. Collecting and
removing infected plant parts can slow the spread
of the disease. This should be done frequently
especially during fruit bearing time.
2. Improve air circulation around the plants. Space
plants widely and prune leaves so that adequate
air flow may speed drying of the vegetation. Work
with plants when they are dry.
3. Avoid spring applications of nitrogen fertilizer.
High nitrogen levels promote excessive leaf
growth and available surfaces for infection.
4. Harvest regularly. Remove and dispose of rotten
or severely damaged fruit throughout the season.
5. Move plants to a better location.Select sites for
planting that have good air circulation, are not
shaded, and not subject to frost injury.
6. Use fungicide sprays, if necessary. Apply a
fungicide at 5–10% bloom and at full bloom.
Fungicides may be reapplied every 7–10 days
during wet seasons. Pesticides registered for use
include captan, chlorothalonil (Daconil), copper,
iprodione (Chipco), mancozeb, sulphur, thiram,
and ziram. | 
