Control Plant Diseases
for better farming and better living
Mimeo BP 3-5 REV Jan 1950

PEACH AND PLUM BROWN ROT

One of the questions most commonly asked by amateur fruit
growers is, "Why do my plums and peaches rot and dry up just as
they are getting ripe?” The brown rot disease that is responsi-
ble for this condition will cause some loss every year in the
home peach and plum orchard, and in some years when humid, rainy
weather occurs, the disease may virtually destroy the crop just
as it ripens.

The Story of Plum and Peach Brown Rot

In home orchards where brown rot has been a problem, the ob-
servant gardener will notice an unnatural browning and wilting of
blossoms just before the petals fall. This is the beginning of
the brown rot story and is related to the later destruction of
fruit at harvest time. Brown rot spores from old peach and plum
mummies, left over from last year's rotten fruits, can infect the
peach or plum flower at blooming time, causing the petals to turn
brown prematurely and the blossom to fall off. About two weeks
after blossom time, the infection will have progressed down the
flower stalk into the twigs and branches of the tree. Twigs in-
fected in this way quickly wither causing a die-back of the young
terminal shoots. In seasons with wet springs and early summers,
these blighted twigs will produce thousands of brown rot spores
throughout the summer months.

As the young green plums or peaches develop, they are attack-
ed by the plum curculio insect, which causes the familiar moon-
shaped scars on the fruit. These fruit later become wormy at har-
vest time. The plum curculio works as a partner with brown rot
since spores produced from blighted twigs enter green fruits
through curculio wounds to cause a few, unnoticed, rotted fruits
early in the season.	1

Approximately three weeks before harvest time, the fruit be-
comes naturally susceptible to brown rot and can become infected
without help from the curculio and other insects. Wounds, such
as limb bruising and hail damage, greatly increase the dangers of
brown rot losses at harvest time. Spores for infection of fruit
at harvest are carried by winds, rain and insects from blighted
twigs and from green fruits that become infected through curculio
wounds. Once brown rot starts on mature fruit, it quickly spreads
to other fruits. Invisible brown rot infections on mature fruit
may be present at harvest time, in which case, the fruit will rot
within a day or two after being picked.

PURDUE UNIVERSITY Agricultural Extension Service, Lafayette, Indiana
Department of Botany and Plant Pathology, Life Science Building