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Botrytis
Botrytis is a fungus (Botrytis cinerea), sometimes
known as gray mold, that infects tender, fleshy portions of plants
especially flowers and fruits. It thrives in humid, cool conditions
and and in standing water on plants. Botrytis spreads by spores
that are released into the air or splashed onto plants.
Pathogen:
Botrytis cinerea is the fungal pathogen that causes gray
mold. The fungus lives on plant debris and attacks tender, fleshy
portions of plants. Damaged areas of plants are also susceptible
to Botrytis. Prevent the introduction of Botrytis into your garden
by examining all plants before you purchase them. Do not buy plants
with mold on them. Examine the flowers, leaves, and stems for
dark, mushy areas.
Keeping dead leaves and debris picked up from beneath plants will
help prevent Botrytis. Also, remove dead flower heads, especially
from plants with large flower clusters like geraniums. Prevent
the spread of the fungus by cleaning your pruners before moving
to the next plant. Dip the blades in a bleach solution (1 part
bleach to 6 parts water.) Do not add debris to compost.
Environment:
Botrytis loves cool wet areas with poor air circulation. To eliminate
these conditions space plants apart enough for good air circulation.
A good rule of thumb is to install plants no closer than their
mature width. Measure from the center of each plant. If you want
an instantly full area and are planting slow growing, young plants,
you may install more plants closer together. Only be certain to
thin them out, i.e. transplant every other one, when they begin
to get crowded.
Do not allow the foliage of plants to stay wet, especially over
night. The best way to accomplish this is to avoid overhead watering
and water early in the morning instead of in the evening.
Hosts:
Botrytis will attack almost any annual, perennial, or fruit. Notable
plants are geraniums, begonias, peonies, grapes and strawberries.
Resistant varieties are available for some of these plants and
research is still underway to improve resistance.
Management:
Before treating with a fungicide remove any dead plants and infected
plant parts. Do not add to compost. For annuals and perennials,
apply chlorothalonil (Daconil). Grapes, strawberries and other
fruits require a fungicide labeled for edible plants, i.e. captan.
Apply fungicides according to label directions.
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| Controlling Existing Pathogenic Diseases
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