of Rhode Island GreenShare Factsheets
Rot of Stone Fruits
Brown rot (Monilinia fructicola) is a common and
destructive disease of peach and other stone fruits (plum, nectarine,
apricot and cherry). The brown rot fungus may attack blossoms,
fruit, spurs (flower and fruit-bearing twigs) and small branches.
The disease is most important on fruits just before ripening
and during and after harvest. Under favorable conditions for
disease development, an entire crop can be completely rotted
on the tree. Peaches not kept in cool storage may be rotted in
two to three days by the fungus.
The symptoms of brown rot are very similar on all stone
fruit. Symptoms first appear in the spring as the blossoms open.
Diseased flowers wilt and turn brown, and are often covered with
masses of brownish-gray spores. The diseased flowers usually
remain attached into the summer.
Young fruits are normally resistant,
but may become infected through wounds. Fruits become more
susceptible to attack as they
mature, even in the absence of wounds. Fruit infections appear
as soft brown spots, which rapidly expand and produce a tan powdery
mass of conidia. The entire fruit rots rapidly, then dries and
shrinks into a wrinkled "mummy." Rotted fruit and mummies may
remain on the tree or fall to the ground. Fruit infection may
spread rapidly, especially if environmental conditions are favorable
and fruits are touching one another.
The fungus may move from diseased blossoms or fruit into
the spurs. The fungus may then invade and cause diseased areas
(cankers) on the twigs below. Succulent shoots are sometimes
infected by direct penetration near their tip. A canker may form
encircling the twig, causing death of the twig beyond the canker
The brown rot fungus survives the winter in mummified fruits
(either on the ground or still on the tree) and in twig and branch
cankers produced the preceding year. Both sources may produce
spores that can infect blossoms and young shoots. At about blossom
time, a mummified fruit that has fallen on the ground produces
up to 20 or more small, tan, cup-like structures on slender stalks
that are called apothecia. As an apothecium matures, it becomes
thicker and the cup opens to a bowl-like disc 3 to 12 mm (l/8
to l/2 inch) in diameter across the top. The inner surface of
each bowl is lined with thousands of spore-containing sacs (asci).
At this stage, the slightest disturbance or air movement will
cause an apothecium to forcibly discharge millions of spores.
These spores (ascospores) are carried by wind to the open
or unopened blossoms and young shoots. If a film of water (either
from dew or rain) is present for 5 hours or longer, the spores
can germinate and penetrate the plant. Infected blossoms soon
wilt and tan-gray tufts, composed of masses of another type of
spore (conidia), develop on the outside of the flower shuck.
If the infected blossom does not drop off, the fungus soon grows
through the pedicel to the twig and forms a canker.
Masses of conidia are soon produced on the newly cankered
twig surface during moist periods throughout May and June. These
summer spores are easily detached and, like the ascospores, are
mainly wind-borne. They are also splashed by rain or carried
by insects to the growing fruit. Brown rot conidia can germinate
and infect at temperatures of 32 to 90 degrees F. Wet weather
and temperatures ranging from 60 to 70 degrees F are most favorable
for disease development.
Following spring and summer rainy periods,
mummified fruit still hanging in the tree become covered with
masses of conidia
that may result in blossom blight or fruit rot. Mummies hanging
in the tree do not produce ascospores. Although the flesh of
young fruit is very susceptible to brown rot infection, the fruit
has such a tough skin that the germ tubes of the summer spores
do not normally penetrate. Young, uninjured fruits are thus fairly
safe from infection.
Any type of injury to the fruit, however,
will provide entry points for brown rot spores. Insect and hail
wounds, fruit cracking,
limb rubs, twig punctures and a variety of picking and packing
injuries greatly increase the losses due to brown rot. Growers
must realize that brown rot spores are practically everywhere
during the fruit-ripening period. Infection is almost certain
to occur if the weather is moist and if the fruit skin is broken
in some way.
1. Sanitation is very important in controlling brown rot.
All dropped and rotted fruit should be picked up and destroyed
promptly. At the same time, remove all mummies from the trees.
Prune out all cankers during the dormant season. Overripe or
rotting fruit in the packing shed should be removed and destroyed
2. Control of insects that feed on fruit is essential. Remember
that anything that causes wounding of the fruit will increase
the incidence of brown rot. Special care should be taken during
harvesting and packing to prevent puncturing or bruising of ripe
3. Remove wild or neglected stone fruit trees that serve
as reservoirs for the disease.
4. Fruit should be cooled and refrigerated (as close to
32 degrees F as possible) immediately after harvest.
5. The use of fungicide is an important part of the disease
management program for brown rot. Call the URI Cooperative Extension
Gardening Hotline for the most current recommendations.
Adapted from Michael
A. Ellis, Ohio State University Extension, 2001
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
of Rhode Island Cooperative Extension provides equal program