Brown rot and white rot

1. Man, Microbes and
Environment

2. Brown rots & White rots

3. BROWN ROTS

4. Introduction
● Brown rot is one of the most important diseases of Stone fruit
(summer fruit).
● Stone fruits such as apricot and peaches originated in China and
spread through old trade routes 3–4000 years ago. Nectarines
are more recent (at least 2000 years). Cherries and European
plums originated in Europe, although the Japanese plum
originated in China.
● Field losses can be extensive if conditions favorable for disease
development occur during the blossoming or preharvest and
harvest periods.
Causitive agent
● Monilinia fructicola is a species of fungus in the order
Helotiales.

5. Symptoms
● Typical disease symptoms induced by M. fructicola include blossom
and twig blight, cankers, and a fruit rot.
● The fungus often produces conidia profusely on sporodochia(A small,
compact stroma, having conidiophores on which the asexual
spores or conidia are formed) on infected areas.
● The first indication of the disease in the spring is
■ the rapid death of blossoms which, as they turn brown, often
become affixed to the twig in a gummy mass, later becoming
covered with a grayish to tan spore mass.
● Frequently, following colonization of the blossom, the fungus enters
the shoot where it causes a canker on which spores are also produced.
Shoot blight symptoms will occur if the fungus girdles the shoot.
● Leaves on such shoots turn tan to brown and may remain attached for
several weeks.
● Cankers formed following blossom or fruit infection appear as brownish,
sunken areas, that are often covered with gum. These cankers support
the formation of conidia in wet weather and harbor the fungus over the
winter.

6. ● Usually, the tree is able to restrict cankers to small oval areas at the
junction of the shoot and the infected blossom or fruit. Cankers and
killed shoots may be colonized by other aggressive canker-causing
fungi such as Leucostoma spp.
● Brown rot on ripening or mature fruit typically develops as a
rapidly spreading brown necrosis. Under optimum conditions for the
fungus, entire fruit may be rotted within 48 hours of infection. The
infection produces a soft dry rot, although occasionally the skin
remains firm.
■ On nectarines, brown rot sometimes occurs as quiescent
infections which can be detected as small, circular, necrotic
lesions on immature fruits. As fruits mature, decay spreads
from the lesion throughout the entire fruit.
● Immature or mature fruit with brown rot infections will sporulate
profusely, shrivel, and become tough grayish-black mummies. These
mummies may drop to the ground, where apothecia may develop,
or remain attached to the tree through the winter. Decaying fruit
in cold storage or transit may appear black with little or no
sporulation.

7. Disease Cycle
● M. fructicola overwinters in orchards as mycelium on mummies, fruit
stems, blighted blossoms and twigs, and cankers. Sporodochia
develop under cool, wet conditions during the winter and early
spring.
● Occasionally, cup-like apothecia of M. fructicola which produce
ascospores can be found on fruit mummies under the tree.
● Generally, conidia from mummies and cankers on stone fruit trees
and other sources (for example, flowering ornamental plants of plum
or quince, or wild plantings of plum) are believed to be the primary
inoculum sources.
● Conidia of M. fructicola are generally formed during late spring when
temperatures range from 55 to 77 F (13-25 C). Conidia are
disseminated by wind and rain and germinate rapidly under
favorable conditions.
● Optimum temperatures for blossom infection of peach range from 72
to 77 F (22-25 C). Between 32 to 86 F (0-30 C), temperatures above
or below the optimum range delay germination but do not inhibit it.

8. ● Under optimum temperature conditions, fruit infections can occur
with only three hours of wetness when inoculum levels are high.
Longer wet periods during infection result in shorter incubation
periods so symptoms develop more rapidly. Large amounts of
inoculum with highly favorable environment produces a high
potential for heavy losses.
● Although blossom blight can be severe enough to reduce the crop,
early sporulation on even a few infected blossoms provides more
inoculum for later fruit infections.
● The subsequent invasion of shoots also enables the pathogen to
survive in the host for long periods. In some areas, infections of
flowers may result in active or quiescent infections that either cause
decay of green fruit or become active prior to harvest.
● Sporodochia of M. fructicola on infected blossoms and shoots may
produce viable conidia throughout the remainder of the growing
season, although sporulation from infected blossoms tends to
decline over the summer.

9. ● Infection may occur by direct penetration of the germinating spore
through the cuticle or lenticels in the fruit.
● Insects (nitidulid beetles and honey bees) also can be important as
vectors of the fungus during fruit ripening, carrying conidia to injury
sites produced by oriental fruit moth,
● Japanese beetle, green June beetle, and other insects that injure
fruit. Wounded fruit are infected much more readily than
nonwounded fruit.
● At harvest, apparently healthy fruit usually are contaminated with
spores which, under favorable conditions, may later decay during
storage and marketing.

10. Monitoring
● During or after pruning (before the pink 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 more than
ten mummies and/or cankers represents levels of moderate and
high risk, respectively, for blossom infection under the
appropriate environmental conditions.
● Before 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.
Monitoring for and removal of cankers is best done at the same time.
● At shuck fall(falling of. Floral. Parts. For. Fruit formation) , 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.

11. ● 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
● An estimate of the potential for postharvest rot to develop can be
determined by harvesting 10 mature, healthy fruit from each sample
tree.
Brown rot may develop during storage and shipment if fruit are not
handled properly during and after harvest. Monitor daily for developing
decay in packed fruit being temporarily stored by checking fruit
throughout a minimum of containers

12. Management
● Cultural practices
● Chemical management

16. WHITE ROTS

17. Introduction
The fungus causing white rot is ubiquitous in nature, occurring on
a wide variety of woody plants including birch, chestnut, peach,
and blueberry.
White rot is often referred to as Botryosphaeria rot or Bot rot
and is a serious pathogen of apple fruit and wood. The canker
phase of the pathogen can also cause considerable loss in many
regions of the south, midwest, and northeast. Drought stress and
winter injury have also been associated with an increase in
infection and canker expansion.
Causative agent
● Caused by Botryosphaeria dothidea

18. Symptoms
● The white rot fungus only infects fruit and wood. New infections on
twigs and limbs become evident in early summer and originate
around lenticels, appearing as small, circular spots or blisters.
● As the lesions expand, the area becomes depressed and a watery
exudate may appear on the bark around the blisters.
● In four to eight weeks, black fruiting structures can be observed
within cankers
● Cankers stop enlarging by late fall and are indistinguishable from
black rot cankers (caused by B. obtusa), making isolation of the
pathogen necessary for the correct identification of the causal
organism.
● As the cankers progress, they exhibit a scaly, papery outer bark that
is orange in color and often sloughs off.
● Under favorable conditions for disease development, cankers will
fuse and the girdling of large limbs can occur. The sudden
appearance of bright yellow foliage on some apple limbs in late May
to early June is one of the more striking symptoms of white rot and
occurs when a canker associated with a wound girdles the limb.

19. ● Symptoms of fruit rot infection can be seen four to six weeks before
harvest and depend on the developmental stage of the fruit.
● Lesions begin as small, slightly sunken brown spots that may be
surrounded by a red halo. As the decayed area expands, the core
becomes rotten and eventually the entire fruit rots.
● Black fruiting structures may be observed on the surface of the rotted
fruit in advanced stages. Red-skinned apple cultivars may "bleach"
during the decay process and become light brown in color.
Because of this characteristic, the disease is sometimes referred to as
"white rot."
● Decayed flesh associated with white rot is very soft and watery
under warm conditions.
● When fruit rot develops under cool conditions, however, the rotted
area is much firmer and is very similar to black rot infection
On certain apple cultivars, even with these criteria, it is difficult to determine
which fungus initiated the infection.
● Rotted fruit usually drop from the tree, but some will mummify and
remain attached.

20. Disease Cycle
● The disease cycle for white rot is almost identical to that of black
rot. The host range of white rot is broad, but the role these other
hosts play in the development of the disease in apples is not known
● The white rot fungus overwinters in cankered wood, wood that
had been previously killed by fire blight, dead bark, and in
mummified fruit.
● Ascospores and conidia are produced on these structures
throughout the growing season.
■ The optimum temperature for germination of both spore
types is 82 to 90 F (28-32 C), which can occur in as little as
90 minutes at 82 F (28 C).
● During wet periods, spores ooze out of fruiting structures and are
dispersed by rainfall.
● Infection of wood can occur through lenticels and wounds. It
has also been observed that moisture stress (drought) and winter
injury facilitate canker development, especially on older limbs.

21. ● It is not known exactly when fruit infection occurs.
● Some theories propose that
■ infection can occur anytime from the bloom period to harvest,
● while other theories state that
■ fruit infection only occurs during the last six to eight weeks of
the growing season, and that the degree of infection is
dependent on the sugar content of fruit of individual cultivars.
● There are also differences in cultivar susceptibility to white rot
infection.
● For fruit infection to occur, wounding is not necessary; however,
when wounds are present, they are colonized rapidly by the fungus.
● Infection of wounded fruit can occur in as little as two hours at 82 F
(28 C); however, 16 hours of a wetting period is necessary for
infection to occur at 46 F (8 C)

22. Monitoring
● Monitor each tree for cankers. Remove cankered wood from the
orchard or mulch the brush so that it decays over the period of a
year.
● Inspect trees for apple mummies and remove them from the orchard
if possible, since mummies remaining in the trees from the previous
season can also serve as a source of inoculum.
● During early midseason, observe 25 fruit on each sample tree. Fruit
is most commonly infected at an injury, but infection can occur
without the fruit being injured.
● Where white rot has been a problem, observe 'Golden Delicious'
trees for an early indication of the disease.
● Record the location of trees with an abundance of dead wood and
cankers so these can be scheduled for intensive pruning during the
dormant period.