Transcript Disease Cycle

6.2 Diseases of Stone Fruits
• PEACH AND NECTARINE
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ANTHRACNOSE
BACTERIAL SPOT Xanthomonas pruni
BROWN ROT Monilinia fructicola
FUSICOCCUM CANKER
LEAF CURL
LEUCOSTOMA CANKER
PLUM POX VIRUS (PPV)
POWDERY MILDEW
PRUNUS STEM PITTING VIRUS
RHIZOPUS FRUIT ROT
SCAB
VERTICILLIUM WILT
X-DISEASE
YELLOWS Witch's broom
CHERRY
•BACTERIAL CANKER
•BLACK KNOT
•BROWN ROT
•LEAF SPOT
•POWDERY MILDEW
•PRUNUS NECROTIC RINGSPOT VIRUS
•SILVER LEAF
PLUM
•BACTERIAL SPOT Xanthomonas pruni
•BLACK KNOT
•BROWN LINE or CONSTRICTION DISEASE
•BROWN ROT
•PLUM POX VIRUS (PPV)
•PRUNE DWARF VIRUS
6.2.1 Brown Rot of stone fruits
I. Introduction:
• Brown rot is one of the most important diseases of
stone fruits in the mid-Atlantic region.
• Field losses of nectarines can be extensive if
conditions favorable for disease development occur
during the blossoming or preharvest and harvest
periods. Losses of peach vary with susceptibility of
the cultivar.
Symptoms
• Typical disease symptoms include blossom and
twig blight, cankers, and a fruit rot. T
• he fungus often produces conidia profusely on
sporodochia 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(茶色) spore mass.
Symptoms
• 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.
Symptoms
• 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.
Symptoms
• On nectarines, brown rot sometimes occurs as
quiescent infections which can be detected as
small, circular, necrotic lesions on immature fruits.
• Immature or mature fruit with brown rot infections
will sporulate profusely, shrivel, and become tough
grayish-black mummies.
• Decaying fruit in cold storage or transit may
appear black with little or no sporulation.
Peach brown rot
(2005.06,Meixian,
Shaanxi )
Plum brown rot (2005.06,Meixian,Shaanxi )
Cup-like apothecia
which produce
ascospores formed on
fruit mummies
Twig blight
Disease Cycle
Monilinia 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 which produce
ascospores can be found on fruit mummies under
the tree, but they are not usually common in midAtlantic commercial orchards.
Disease Cycle
• In years when apothecia were common, severe
blossom blight was noted in peach and apricot
orchards, but severe blossom blight also can
occur in the absence of apothecia.
• 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 are generally formed during late spring
when temperatures range from 13-25 C.
Disease Cycle
• Conidia are disseminated by wind and rain and
germinate rapidly under favorable conditions.
• Optimum temperatures for blossom infection of
peach range from 22-25 C. Between 0-30 C,
temperatures above or below the optimum range
delay germination but do not inhibit it.
• Inoculum concentration also interacts with
temperature and wetness duration to influence
incubation period and disease incidence and
severity.
Disease Cycle
• Although blossom blight（花腐）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.
Disease Cycle
• Quiescent infections of peach and nectarine have
not been reported in the eastern U.S., perhaps
because blossom infection is less common here
than in other locations
• Under optimum temperature conditions, fruit
infections can occur with only 3 hours of wetness
when inoculum levels are high.
• Longer wet periods during infection result in
shorter incubation periods so symptoms develop
more rapidly.
Disease Cycle
• Large amounts of inoculum with highly favorable
environment produces a high potential for heavy
losses.
• 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.
Disease Cycle
• Insects (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, 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.
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.
Monitoring
• 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.
• 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.
Monitoring
• 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.
Monitoring
• 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.
Management
• Cultural practices.
• Sanitation is essential if your orchard is to be
considered a low risk for a brown rot epidemic.
The practices listed below, if followed, should
minimize brown rot spore populations and limit the
likelihood of an epidemic when conditions are
favorable for rapid disease development.
Management
 Remove all remaining fruit from the tree after the
final picking.
 This practice limits infection of fruit peduncles（梗）
and twigs thus reducing the number of brown rot
cankers.
 In addition, this practice prevents the situation
where overwintered mummies within the tree
would be immediately adjacent to susceptible
blossoms in the spring.
Management
• Furthermore, removal of remaining fruit after final
picking separates the practice of removing
mummies from spring pruning.
• Where these practices are separated, the grower
has more latitude to selectively prune (following a
severe winter with high bud mortality（死亡率）,
for example) without increased risk of blossom
infection.
Management
• Fruit thinning practices influence the carry over of
brown rot during the summer months and into the
fruit ripening season.
• In general, fruit thinned before pit hardening
decompose rapidly; whereas, fruit thinned after pit
hardening become infected on the orchard floor
and serve as spore sources for the disease.
Management
• In spring, monitor for blossom infection and prune
out any cankers and infected shoots.
• In spring, just prior to and during the blossom
period, examine the orchard floor for apothecia.
Their presence requires that blossoms be
thoroughly protected with fungicide sprays during
wet periods.
• Prune to avoid excessive overcrowding of
branches to increase air circulation, promote rapid
drying, and increase light and spray penetration.
Management
 Fertilize to maintain optimum nitrogen/ potassium
balance.
 Avoid dumping rotten fruit in one location, which
could become the starting point for disease and
insect outbreaks in the following season.
 Pick and handle fruit carefully to avoid injuries;
remove field heat from the fruit promptly after
harvest by hydrocooling or forced air cooling; use
clean containers; keep packing areas clean.
Chemical management
 Fungicides are recommended generally in a
protective program for a complex of diseases,
including brown rot, scab, and powdery mildew.
 Fungicides are to be applied prior to fungal
infection that occurs during rain periods.
 Blossom infections are controlled with two or
three fungicide sprays during the bloom period,
with the number of sprays often varying from year
to year depending upon the weather, the
susceptibility of the stone fruit species, the length
of the bloom period and the type of fungicide.
小结
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发生概况：分布？ 危害？经济损失
轻病害识别：为害部位？发病时期？症状特点？
病原：分类地位；形态特点
病害发生发展规律：越冬、传播、入侵
发病及其影响因素：寄主抗病性、气候、栽培管
理、
• 综合防治：清除越冬菌源；加强栽培管理，提高
树体得抗病能力；选用抗病品种；化学防治；加
强贮运管理
6.2.2 Peach leaf curl
Significance
• Peach leaf curl is a fungus disease that, under the
right conditions, can cause severe early defoliation
and crop loss on nearly all peach and nectarine
cultivars.
• Because of weather factors and good grower
management practices in most years, however, the
disease often causes little or no significant damage
or loss.
• For this reason, the destructive potential of leaf curl
is frequently underestimated to the point where
important control measures may be forgotten or
delayed.
Symptoms
• Infected leaves are severely deformed and often
display a variety of colors ranging from light
green and yellow to shades of red and purple.
• The fungus causes the meristematic cells at leaf
margins to proliferate quickly and randomly,
which results in the leaves becoming variously
wrinkled, puckered, and curled
Symptoms
• As these infected leaves mature, naked asci
containing ascospores of the pathogen are
produced on the surface giving them a dusty
appearance, after which the leaves turn brown,
shrivel, and drop from the tree.
• Many infected fruits drop early and go unnoticed;
those that remain may become crooked at the
stem end like a small yellow squash, while others
develop reddish to purple, wart-like deformities on
the fruit surface .
Pathogen
Taphrina deformans(Berk)Tul
Disease Cycle
 The pathogen occurs commonly almost wherever
peaches are grown, and overwinters as
blastospores in protected crevices in the bark and
around the buds.
 Primary infections are the most damaging and
occur during the early spring from bud swell,
when the bud scales loosen, until the first young
leaves are fully emerged from the bud.
 Infections on young peach leaves occur at
temperatures of 50 to 70 F (10-21 C). Little
infection occurs below 45 F (7 C).
Disease Cycle
 The incidence of infection is greatest when rains
wash the overwintered spores into the bud and
cool temperatures lengthen the time that the
emerging leaves are exposed to the pathogen,
before they are fully expanded and can resist
penetration by the fungus.
 When temperatures following bud swell are
warm and early leaf development is rapid,
infections rarely become established, even when
spring rains occur.
Management
• Non-chemical control
 Collect and dispose of infected leaves before the
bloom of spores appears. This is useful because it
limits the number of spores overwintering on the
plant.
Management
 Erect a polythene or glass structure to cover the
top and front of the tree between January and
mid-May.
 Trees so sheltered from rain and dew show only
very mild symptoms in comparison with
unprotected trees.
 Ensure the sides are left open so that pollinating
insects can enter. You should also carry out
hand pollination.
 If a tree suffers leaf loss, boost its vigour with an
application of fertiliser and make sure it is kept
well watered and mulched.
Management
• Chemical control
 Applications of fungicide must be timed carefully.
A copper fungicide (Vitax Bordeaux Mixture,
Murphy Traditional Copper Fungicide) or
mancozeb (Dithane) should be applied as the
buds begin to swell and then repeated 14 days
later.
 Bud swelling normally occurs in late January or
early February but may be delayed in colder
districts.
 Spraying must be completed before flower buds
open. Another application at leaf fall may also be
beneficial.
小结
• 发生概况：分布？ 危害？经济损失
• 轻病害识别：为害？发病时期？症状特点？
• 病原：形态特点
• 病害发生发展规律：越冬、传播、入侵
• 发病及其影响因素：寄主抗病性、早春的气候条
件
• 综合防治：加强果园管理；药剂防治
6.2.3 Peach scab
Symptoms
• The most notable symptoms of peach scab occur
on the fruit, where small, greenish, circular spots
gradually enlarge and deepen in color to black as
spore production begins.
• Fruit lesions are most common on the shoulders
of the fruit, but can occur anywhere on the surface.
Where numerous, they often coalesce and may
lead to cracking of the skin as the fruit enlarges,
allowing rot organisms to enter.
• The overwintering twig lesions are clearly visible
during the early season as small, grayish, more or
less circular, slightly sunken lesions on the
previous season's shoot growth.
Symptoms
Pathogen
• Fusicladium carpophilum，also
called :Cladosporium carpophilum，
• Sexual: (Venturia carpophilum).
• Peach scab is caused by a fungus which can be
extremely damaging to trees throughout the midAtlantic region because of the typically warm, wet
weather during the day through the mid-season
period. The disease appears to affect all cultivars
of peach and is known to occur on nectarines and
apricots as well.
Disease Cycle
• The fungus overwinters in twig lesions.
• In the spring, spores are produced on the lesion
surface (primary inoculum) and are washed or
splashed primarily by wind-blown rain to fruit, leaves,
or new growing twigs.
• On peaches, fruit are first susceptible starting 5-7
days after shuck split.
Disease Cycle
• Periods of rainfall with temperatures of 65-75 F are
optimal conditions for infection.
• Although fruit remains susceptible until harvest, the
4-week period following start of shuck split is the
most critical period for infection to occur.
• The time from infection until lesions are visible may
be 4-6 weeks. Thus, infections occuring within 4
weeks of harvest do not result in visible lesions.
Management
 All varieties are susceptible to scab, with some
being more severely effected than others.
 Generally, scab is most severe the first year the
trees bear fruit (usually 3rd growing season).
 This results from the large numbers of twig
lesions that develop during the first two growing
seasons.
 Low-lying planting sites should be avoided and
trees should be properly pruned to allow good
air circulation, thus promoting rapid drying of
fruit, twigs and leaves.
Management
 Fungicides such as captan and wettable sulfur provide
adequate control of this disease if applications are
properly timed.
 On peaches, sprays should begin about 1 week after
petal-fall.
 Sprays on nectarines and apricots should begin at about
petal-fall.
 Subsequent sprays should be applied at 10-14 day
intervals until approximately 1 month before harvest.
 During the month before harvest, sprays applied for
brown rot control will help reduce late season scab
infections on the fruit, twigs and leaves.
小结
• 发生概况：危害？
• 轻病害识别：为害？发病时期？症状特点？
• 病原：种类
• 病害发生发展规律：越冬、传播、入侵
• 发病及其影响因素：寄主抗病性、早春的气候条
件
• 综合防治：加强果园管理；药剂防治
6.2.4 Crown gall
Significance
 Crown gall is worldwide in occurrence, attacking
140 plant genera in 60 different families.
 Plants most commonly damaged in Texas by
crown gall are pecan, peach, blackberry, grape,
apple, pear, willow, pyracantha, euonymus, rose, fig,
and crabapple.
Significance
 Damage to infected plants results from
interruption of water and nutrient movement up
the stem.
 Galls also interfere with normal growth and
development, therefore, infected plants may be
stunted and unthrifty.
 With many plants, the amount of damage
depends on where the gall or galls are located
and how many are present.
 Death can result if galls girdle the primary trunk
or stem. Infected plants are more sensitive to
winter injury and drought stress.
Symptoms
 Crown gall first appears as small round
overgrowths on stems and roots.
 As they enlarge, the galls become woody with a
rough and irregular surface.
 Aerial galls can develop but most are found at or
just below the soil line. Galls range from peasize to larger than 1 foot in diameter.
Pathogen
• Agrobacterium tumefaciens
Disease Cycle
 Crown gall bacteria infect plants through wounds,
such as those arising from cultivation,
transplanting, wind damage, insect injury, etc.
 Wounds that have healed beyond a certain point
are no longer susceptible to invasion.
 After establishing itself in the wound, the
bacterium transforms normal plant cells to tumor
cells.
Disease Cycle
 Once this has taken place, the tumor cells are
able to reproduce without the bacterium being
present.
 Although crown gall of plants is very much like
cancers in humans and other animals, there is
no relationship between crown gall and animal
cancers.
 Crown gall has been studied extensively by
scientists in their search to understand
cancerous growths.
Management
 Control is primarily dependent on prevention.
Pruning off galls is not effective since the
bacterium is systemic and gall tissue can
reproduce itself.
 Chemical control with antibiotic drenches has
shown promise; however, they are not practical
at this time.
 Inspect plants for crown gall before purchasing.
Plant only crown gall-free trees and shrubs.
 Remove and destroy heavily infected and
weakened plants. Dig up as many roots as
possible.
Management
 Replace with a more resistant type plant if
possible.
 Avoid wounding plants while mowing, cultivating,
etc.
 Keep plants in an active growing state with
proper fertility and watering.
 Heavily infected nursery fields should be planted
to a grass crop for three years before planting
susceptible nursery stock.
Management
 Control root feeding insects.
 Dip grafting and pruning tools regularly in a
disinfecting solution, such as 70 percent alcohol,
10 percent sodium hypochlorite (common bleach)
or potassium permanganate solution (1 ounce in
2 gallons of water).
小结
• 发生概况：分布？ 危害？
• 轻病害识别：发病时期？症状特点？
• 病原：细菌病害；生理特性（Ti-质粒）
• 病害发生发展规律：越冬越夏、入侵部位、传播、
• 发病及其影响因素：温湿度；土壤理化性质；嫁
接方式
• 综合防治：选用无病苗木；苗木消毒；处理土壤；
生物防治；及时防治地下害虫