Botrytis (Gray Mold): A Disease
for Many Plants
Botrytis is a fungus. This fungus can attack a wide range of plant
parts. It can attack buds, flowers, and leaves, stems and fruit.
However, botrytis can be confused with other diseases that cause
similar damage. There are more than one species of botrytis and
many different strains of each.
Botrytis may attack the foliage of nursery stock stored over winter
in damp conditions. Botrytis may attack greenhouse crops where humidity
is kept on the high side and then condensation forms at night as
temperatures cool off. Free moisture allows botrytis to grow even
better. Cool temperatures may slow the disease down but as long
as it is moist the disease continues to infect and spread. Botrytis
is active from 32 degrees Fahrenheit to about 80 degrees. Hot dry
weather shuts the disease down.
Botrytis often lives on dead plant material and from there, spreads
into weakened living plant material. It can also infect through
wounds or healthy tissue without going though dead or dying tissue.
This fungus disease can cause twig blights on stems, buds, flowers,
fruit and leaves. It can cause gummosis, fruit rot and damping off.
Spores spread from infected tissue to none infected tissue via wind
and water. Spores are released with rapidly decreasing or rising
humidity levels as well as rain drops hitting the spore structures.
Under the right conditions, any disturbance of the air around the
spore structures can cause hundreds of thousands of spores to be
released. When humidity is high, a thin to thick web of mycelium
develops on diseased tissue. This mycelium is grayish in color,
hence the name gray mold.
Botrytis produces conidia for adverse conditions such as low moisture
and a resting body for the winter. On dead plant material, the disease
can over winter as mycelium (fungal growth). Botrytis does not need
to attack living plant material since it can live on dead plant
material very well as a saprophytic fungus.
There are no known resistant plants. Control of this disease is
to control the environment. Keep plants healthy avoiding any stresses
such as too wet, too dry, chemical or mechanical injury, and too
little or too much fertilizer. Improve air circulation and sunlight.
Avoid over head watering. Especially keep open flowers with many
petals dry. There are some fungicides to help prevent or reduce
leaf, fruit and stem infections.
December 2000 - January 2001: Winter
Gardening Tips | Plants and Light |
Botrytis (Gray Mold): A Disease for Many Plants | Choosng
a Christmas Tree Variety | Key Questions
for Garden Catalogs