I. Introduction: Brown rot is one
of the most important diseases of plums in the mid-Atlantic region. Field losses of
European and Japanese plums can be extensive if conditions favorable for disease
development occur during the blossom period, following shuck fall, or during the
preharvest and harvest period.
II. Symptoms: Brown rot on ripening fruit may not
occur as distinct spreading lesions as seen on other stone fruits. Instead, infected fruit
appear covered with tufts of grayish to tan fungal spores. See the
peach and nectarine section for additional information.
III. Disease Cycle: See the peach and nectarine
IV. Monitoring: During or after pruning (before the
white bud stage), monitor a minimum of 20 sample trees per block for the presence of fruit
mummies and cankers. A total of one to ten mummies and/or cankers, and greater than ten
mummies and/or cankers represents levels of moderate and high risk, respectively, for
blossom infection under the appropriate environmental conditions.
At bloom, monitor the orchard floor under sample trees for
the presence of apothecia of the brown rot fungus. These are more likely to occur in the
wettest areas of the orchard on mummies partially buried in soil and/or among weeds.
Finding any apothecia represents a potential high risk for blossom infection. Remove
cankers surgically if possible or prune out the entire diseased area. Monitoring for and
removal of cankers is best done at the same time.
At shuck fall, examine ten shoots on each sample tree for
the presence of blossom infection. A total of one to ten blossom infections and greater
than ten blossom infections represents moderate and high risk, respectively, for fruit
infection during the preharvest and harvest periods.
During the preharvest period, fruit susceptibility to brown
rot increases rapidly as fruit begin to color. Monitor ten fruit on each sample tree for
disease incidence. Greater than two infected fruit per ten acres (eight trees sampled)
represents a high risk for a brown rot outbreak at this time. Monitor approximately every
three to five days during the preharvest period. Insect, bird and hail damage to ripening
fruit can result in wounds which can be quickly colonized by the rot fungus. Brown rot
will show up first in areas near sources of inoculum and where fruit may be physically
Brown rot may develop during storage and shipment if fruit
are not handled properly during and after harvest. Monitor daily for developing decay in
fruit being temporarily stored by checking fruit throughout a minimum of containers.
V. Management: See the peach and nectarine section for suggested management practices
for brown rot.
Chemical control -
Chemical control - home
orchardists (pdf file - Acrobat Reader required)
Text prepared by A.R. Biggs, K.D. Hickey,
and K.S. Yoder
Download this file in pdf format (Acrobat Reader required)