Transcript Disease Cycle

7-2 Solanceous Fruits Diseases
7.2.1 Tomoto Leaf Mould
 Leaf mould is a disease of tomatoes only.
 The disease is a common and destructive disease on
tomatoes worldwide grown under humid conditions.
 Leaf mold is primarily a problem on greenhouse tomatoes,
but occasionally develops on field and garden-grown
tomatoes if conditions are favorable.
 he disease is most destructive in the greenhouse during the
fall, early winter, and spring when the relative humidity is
most likely to be high, and air temperatures are such that
heating is not continuous.
Tomoto Leaf Mould
 When humidity is high, the fungus develops
rapidly on the foliage, usually starting on the lower
leaves and progressing upward.
 If the disease is not controlled, large portions of
the foliage can be killed, resulting in significant
yield reductions.
 Early infections are most threatening.
Symptoms
 Major symptoms occur on the foliage but they
may also occur on petioles（叶柄）, stems, and
fruit peduncles（果梗） (but not on the fruit itself).
 All stages of growth are attacked.
Symptoms
 The first leaf symptom is the appearance of small,
white, pale green, or yellowish spots with indefinite
margins on the upper leaf surface.
 On the corresponding areas of the lower leaf
surface the fungus begins to sporulate.
 The fungus appears as an olive green to grayish
purple velvety growth composed mostly of spores
(conidia) of the leaf mold fungus.
Symptoms
 Infected leaf tissue becomes yellowish brown, and
the leaf curls, withers, and drops prematurely.
 The withering and defoliation progress up the
plant until the entire plant may appear dry and
dead.
 Disease development is slow and severe
symptoms are usually present only late in the
season; however, major yield losses are possible
if infection occurs early.
 Seed-borne infection has not been reported.
Pathogen
Fulvia fulva，synonym Cladosporium fulvum
Spores germinate in water films or when
humidity levels are above 85 percent, at
temperatures between 4 and 34℃. The optimum
temperature for germination is between 24 and 26 ℃.
Disease Cycle
 The fungus survives between seasons as conidia
(spores), as sclerotia on plant debris, in seed, and
as a soil saprophyte.
 Conidia are resistant to drying, and may survive in
the greenhouse at least 1 year in the absence of a
susceptible host, and new conidia can be produced
from surviving sclerotia.
 The conidia act as primary inoculum to infect
plants when conditions become favorable.
Disease Cycle
 Leaves are infected through stomata when
humidity levels are 85 percent or higher.
 Infection occurs most rapidly when humidity
levels at the leaf surface fluctuate between 85
percent (day) and 100 percent (night).
 Symptoms usually begin to appear approximately
10 days after inoculation, with spore formation
beginning a few days later.
 Spore production is most abundant at relative
humidity between 78 and 92 percent, but can
occur at humidity as low as 58 percent.
Conditions for
Disease Development
 Many cycles of disease development are possible during the
growing season.
 Disease development is influenced by temperature, relative
humidity, and long periods of leaf wetness.
 The presence of moisture on the foliage from dew, rainfall
and fog provides good conditions for disease development.
 Increasing periods of leaf wetness are associated with
increasing disease severity; consequently, the disease may
become more serious during the rainy season when warm
temperatures prevail. I
 ts spores will not germinate if the relative humidity is less
than 85%.
CONTROL
1. Whenever possible, keep the relative humidity in
the greenhouse below 85 percent. This will inhibit
the development and spread of the leaf mold
fungus.
a. Provide good ventilation and as much light as
possible.
b. Attempt to avoid wetting the leaves when watering.
Water early in the day to allow leaves to dry by
mid-afternoon.
CONTROL
• c.Maintain a temperature of at least 16 to 18℃
throughout the season.
• d.Provide adequate plant and row spacing to
avoid excessive shading.
CONTROL
2. Leaf mold resistant varieties are available, but
because the fungus mutates readily (there are at
least 12 races of the pathogen) resistant varieties
are of limited use. Because new virulent races
can develop in only a few years, a tomato variety
which is resistant one year may be very
susceptible the next. If available, grow varieties
with more than one leaf mold resistance gene.
CONTROL
3. A fungicide spray program may help control the
disease, but should be considered secondary to
environmental control measures.
A weekly spray program may be necessary. For
current recommendations refer to the above
mentioned circular. Be sure to thoroughly cover
all aboveground parts of every plant, especially
the lower surface of the foliage, with each spray.
CONTROL
4. Reduce primary inoculum levels through sanitation, steam
treatment of greenhouses, and seed treatment.
a. After harvest, carefully remove and destroy (burn) all plant
debris.
b. Where possible, steam entire greenhouse sections between
crops, preferably on a bright, hot day when little steam will
be needed. Close all ventilators, and maintain the
temperature at 57℃ for at least six hours.
c. Where necessary, use hot water treated seed. Treat seed for
25 minutes at exactly 50℃.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：发病时期？症状特点？
• 病原：分类地位；生物学特性
• 病害发生发展规律：越冬、传播、入侵方式
• 发病及其影响因素：气象因素（温暖、高湿）；
栽培管理；寄主抗病性
• 综合防治：选用抗病品种；种子消毒；加强栽培
管理；合理生态管理；消灭菌源；化学防治
7.2.2 Early blight of tomato
Significance
• Early blight of tomato, caused by the fungus
Alternaria solani, is perhaps the most common
foliar disease of tomatoes in the Northeast and
is also common on potatoes. This disease
causes direct losses by the infection of fruits and
indirect losses by reducing plant vigor. Fruit from
defoliated plants are also subject to sunscald.
Symptoms
• Early blight produces a wide range of symptoms at
all stages of plant growth. It can cause dampingoff, collar rot, stem cankers, leaf blight, and fruit rot.
The classic symptoms occur on the leaves where
circular lesions up to 1/2" in diameter are
produced. Within these lesions dark, concentric
circles can be seen. The leaf blight phase usually
begins on the lower, older leaves and progresses
up the plant. Infected leaves eventually wither, die,
and fall from the plant.
Pathogen
• Alternaria solani
(Ellis et Martin)
Jones et Grout.
Disease Cycle
• Environmental Conditions
• Alternaria spores germinate within 2 hours over a
wide range of temperatures but at 80 to 85oF may
only take 1/2 hour. Another 3 to 12 hours are
required for the fungus to penetrate the plant
depending on temperature. After penetration,
lesions may form within 2-3 days or the infection
can remain dormant awaiting proper conditions
(60oF and extended periods of wetness).
Disease Cycle
• Alternaria sporulates best at about 80oF when
abundant moisture (as provided by rain, mist,
fog, dew, irrigation) is present. Infections are
most prevalent on poorly nourished or otherwise
stressed plants.
Disease Cycle
• Survival and Dispersal
• The fungus spends the winter in infected plant
debris in or on the soil where it can survive at least
one and perhaps several years. It can also be
seed borne. New spores are produced the
following season. The spores are transported by
water, wind, insects, other animals including man,
and machinery. Once the initial infections have
occurred, they become the most important source
of new spore production and are responsible for
rapid disease spread
CONTROL
• Use only clean seed saved from disease-free
plants.
• Remove and destroy crop residue at the end of
the season. Where this is not practical, plow
residue into the soil to promote breakdown by soil
microorganisms and to physically remove the
spore source from the soil surface.
CONTROL
• Practice crop rotation to non-susceptible crops
(3 years). Be sure to control volunteers and
susceptible weeds.
• Promote good air circulation by proper spacing
of plants.
• Orient rows in the direction of prevailing winds,
avoid shaded areas, and avoid wind barriers.
• Irrigate early in the day to promote rapid drying
of foliage.
CONTROL
• Healthy plants with adequate nutrition are less
susceptible to the disease.
• Minimize plant injury and the spread of spores by
controlling insect feeding.
• Hand picking diseased foliage may slow the rate
of disease spread but should not be relied on for
control. Do not work in a wet garden.
• Use resistant or tolerant varieties.
• The preventative fungicide used on a seven to ten
day schedule gives effective control.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：为害？发病时期？症状特点？
• 病原：分类地位；生物学特性
• 病害发生发展规律：越冬、传播、入侵方式
• 发病及其影响因素：气象因素（高温、高湿）；
寄主的生育期和长势；寄主抗病性
• 综合防治：选用抗病品种；选用无病种子；加强
栽培管理；化学防治
7.2.3 Botrytis blight
 Botrytis blight, or gray mold, as it is commonly known, has
an exceptionally wide host range with well over 200
reported hosts.
 The fungus can occur as both a parasite and a saprophyte
on the same wide range of hosts.
 This fungus disease is intriguing in that it can cause a
variety of plant diseases including damping-off and blights
of flowers, fruits, stems, and foliage of many vegetables
and ornamentals.
Botrytis blight
It is a major cause of postharvest rot of
perishable plant produce, including tomatoes at
harvest and in storage. The disease can occur both
in the greenhouse and in the field.
Besides tomato, gray mold is of concern to
other vegetables including snap and lima beans(菜
豆), cabbage, lettuce and endive, muskmelon（香
瓜）, pea, pepper, and potato.
Symptoms
 “Ghost spots” appear on fruits after periods of
prolonged high humidity.
 These superficial spots have a pale halo with a
brown to black pinpoint spot in the center.
 On unripe fruit, the halo is pale green or silvery, and
generally the tissue inside the halo is paler green.
 On ripe fruit, the halo is pale yellow. If warm and
sunny weather occurs, then ghost spot symptoms
usually do not develop further, although the
marketability of the fruit may be affected. Fruit rot
does not develop under these specific conditions.
Symptoms
Botrytis may develop on dying flowers and
subsequently infect the fruit calyx. The lesions on
fruit appear as light brown to gray spots, up to 3 cm
in diameter, and irregular in shape. Later, a dark gray,
velvety growth develops on the fruit surface, followed
by a watery, soft rot.
Symptoms
 Foliar symptoms are more common under humid
greenhouse conditions.
 Affected leaves show light tan or gray spots, and
the infected areas become covered by a brown
fungal growth.
 The leaves wither and collapse. The fungus
proceeds into the stem producing tan, elliptical
cankers with concentric rings. Invasion of lesions
by secondary fungi occurs. Stem cankers cause
wilting of vines.
Pathogen
Gray mold is caused by the fungus Botrytis cinerea.
One-celled spores are borne on branched
conidiophores, and the arrangement of the spores
gives the fungus its name, from the Greek botrys,
meaning a bunch of grapes. Use of a hand lens may
reveal the characteristic grape-cluster arrangement
of spores. As the conidiophores dry out, they gently
move and liberate the spores: usually air movements
are sufficient to get the spores airborne.
Pathogen
The fungus often establishes itself on injured
tissues and can persist as a saprophyte for long
periods. Upon occasion, black sclerotia of variable
size form on or just below, the host surface. The
sclerotia have a black rind and a light interior
composed of a dense mass of hyphae, or threads,
of the fungus. Sclerotia measure up to 3 mm
(occasionally 5 mm) in length and are usually
smaller and thinner than those of the white mold
fungus Sclerotinia sclerotiorum.
Pathogen
The
sclerotia
germinate
to
produce
conidiophores or, rarely, give rise to small cupshaped structures (apothecia), which are the sexual
stage of the fungus. Sclerotia are resistant to
environmental extremes and act as overwintering
resting bodies.
Disease Cycle
 The fungus overwinters as sclerotia or as
mycelium in plant debris and may be seedborne
as spores or mycelium in a few crops.
 Other crops may also serve as sources of the
pathogen and are likely to cross-infect.
 The fungus is easily dispersed large distances by
wind. Small pieces of infected plant tissue or
fungal spores from infected plant debris are also
disseminated shorter distances by splashing and
windblown rain. High relative humidities are
necessary for prolific spore production.
Disease Cycle
In the field, spores landing on tomato plants
germinate and produce an infection when free water
from rain, dew, fog, or irrigation occurs on the plant
surface. Optimum temperatures for infection are
between 18 and 24℃, and infection can occur within
5 hours. High temperatures, above 28℃, suppress
growth and spore production.
Disease Cycle
Dying flowers are a favorable site for infection,
but infections can also result from direct contact with
moist infested soil or plant debris.
In the greenhouse, stem lesions develop either
by direct colonization of wounds or through infected
leaves. The presence of external nutrients, such as
pollen grains in the infection droplet, can markedly
increase infection.
Disease Cycle
The type of wound is said to influence stem lesion
development; breaking off leaves is reported to
give a lower incidence of stem lesions than cutting
off leaves with a knife, leaving a stub.
Conditions for
Disease Development
 The fungus has a very wide host range that
includes many vegetable crops.
 Gray mold development, particularly fungus
sporulation and infection, is favored by cool, wet and
humid weather.
 The fungus requires a water film of several hours
for spore germination, and a longer period of
surface wetness for symptom development.
Conditions for
Disease Development
 Optimum relative humidity for spore production is
about 90%, and most spores are produced during
the night when the temperature is lower and the
relative humidity is higher than during the day.
 Temperatures of 17–23℃ are ideal for disease
development. The length of the surface wetness
period needs to be longer at the lower
temperatures for disease development.
Conditions for
Disease Development
 The fungus generally infects plants through
wounds; for example, the rough handling of young
transplants. Penetration of intact tissue is rare.
 Fruit can be infected through the stem scar,
growth cracks, or other breaks in the skin.
 Plants approaching maturity are more susceptible.
The fungus can also penetrate dead flower tissue
or dying foliage.
Conditions for
Disease Development
Excessive application of nitrogen makes plants
such as young transplants more susceptible to gray
mold. Dense plant canopies will limit air movement
within the crop, thus creating
conditions for
extended surface wetness at night and subsequent
increased gray mold severity.
CONTROL
1. There is no known resistance to B. cinerea in
tomato cultivars.
2. In the field, incorporate Botrytis-affected debris
into the soil and allow it to decompose before
establishing a new tomato crop, or burn diseased
plant debris.
3. Plant in fields where good drainage is available
and maintain weed control to minimize periods
when plants are wet due to reduced air circulation.
4. In the greenhouse, maintain a relative humidity of
less than 80%, especially during the night.
CONTROL
5. Fungicide sprays help to control the disease. New
specific fungicides for Botrytis are available but they
should be rotated with general multi-site protectant
fungicides to prevent the development of resistance
in the fungus to the new chemical controls.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：为害？发病时期？症状特点？
• 病原：生物学特性；寄主范围
• 病害发生发展规律：越冬、传播、入侵方式
• 发病及其影响因素：气象因素（低温、高湿）；栽
培管理
• 综合防治：清除病残体；苗床处理；生态防治；加
强栽培管理；化学防治
7.2.4 Tomato Viral Diseases
Several virus diseases of tomato occur in Kansas,
although they generally are not as prevalent as the
wilt and foliar diseases. Three of the more common
virus diseases are tobacco mosaic, cucumber
mosaic, and tomato spotted wilt.
Tomato Viral Diseases
The tobacco mosaic virus can attack a wide range
of plants, including tomato, pepper, eggplant, tobacco,
spinach, petunia, and marigold.
On tomato, virus infection causes light and dark
green mottled areas on the leaves. Stunting of young
plants is common, and often is accompanied by a
distortion and fern(蕨类植物)-like appearance of the
leaves.
Tomato Viral Diseases
Older leaves curl downward and may be slightly
distorted. Certain strains of the virus can cause a
mottling, streaking, and necrosis of the fruits.
Infected plants are not killed, but they produce
poor quality fruit and low yields.
Tomato Viral Diseases
The cucumber mosaic virus has one of the
broadest host ranges of any of the viruses. The
disease affects a number of important vegetables
and ornamentals including tomato, pepper, cucumber,
melons, squash, spinach, celery, beets, and petunia.
Tomatoes infected with the cucumber mosaic virus
develop a slight yellowing and mottling of the older
leaves.
Tomato Viral Diseases
Expanding leaves typically become twisted, curl
downward, and develop a 'shoestring' appearance
as a result of a restriction of the leaf surface to a
narrow band around the midrib of the leaf.
Diseased plants are stunted and produce small
quantities of fruit.
Tomato Viral Diseases
The tomato spotted wilt virus also has a wide
host range and can affect a number of ornamental
plants as well as tomato. Early symptoms of spotted
wilt on tomato are difficult to diagnose. Young,
infected plants may show an inward cupping of
leaves, and the foliage may appear off-color or have
a slight bronze cast. In some cases, leaves with
exhibit dark purple flecks or small necrotic concentric
rings.
Development of Disease
The tobacco mosaic virus is very stable and can
persist in dry contaminated soil, in infected tomato
debris, on or in the seed coat. The virus is
transmitted readily from plant to plant by mechanical
means.
Development of Disease
This may simply involve picking up the virus while
working with infected plant material, then
inoculating healthy plants by rubbing or brushing
against them with contaminated tools, clothing, or
hands. Aphids are not vectors of the tomato
mosaic virus, although certain chewing insects
may transmit the pathogen.
Development of Disease
The cucumber mosaic virus overwinters in
perennial weeds and may be transmitted to healthy
plants by aphid vectors (although tomatoes are not
the preferred host of aphids) or by mechanical
means.
The cucumber mosaic virus cannot withstand
drying, or persist in the soil. It also is more difficult
than tobacco mosaic to transmit mechanically. Thus,
cucumber mosaic tends to progress more slowly than
tobacco mosaic in a field or garden.
Development of Disease
The spotted wilt virus is transmitted from plant to
plant by several species of small insects called thrips.
Thrips are less than one-quarter inch in length, light
green to brown, and are extremely difficult to find on
the plants. Several weedy hosts and ornamental
plants may serve as alternate hosts for the virus.
CONTROL
 Virus diseases cannot be controlled once the plant
is infected. Therefore, every effort should be made
to prevent introduction of virus diseases into the
garden.
 Many varieties of tomato are available with
resistance to tobacco mosaic virus.
 Sanitation is the primary means of controlling the
other two virus diseases. Infected plants should be
removed immediately to prevent spread of the
pathogens.
CONTROL
 Perennial weeds, which may serve as alternate
hosts, should be controlled in and adjacent to the
garden.
 Avoid planting tomatoes next to cucurbits, spinach,
or other vegetables and flowers susceptible to
these diseases.
 Control of insects, especially aphids and thrips,
will help reduce the likelihood of cucumber mosaic
and spotted wilt.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：发病时期？症状特点？
• 病原：毒源种类
• 病害发生发展规律：不同毒源的传播途径、侵染来源
• 发病及其影响因素：种苗带毒情况；寄主抗病性；气象
因素；栽培管理
• 综合防治：选用抗病品种；减少毒源数量；加强栽培管
理；早期避蚜治蚜；化学防治；弱毒株系利用
7.2.5 Phytophthora Blight of Pepper
Introduction
Phytophthora blight, a highly destructive disease
of peppers, has increased in importance in recent
years in Ohio and eastern states.
Other names applied to this disease of peppers
are damping off and Phytophthora root rot, crown rot,
and stem and fruit rot. All of these names can apply
since all parts of the pepper plant are affected.
Phytophthora Blight of Pepper
 P. capsici was first described by Leonin in
1922 on chili pepper in New Mexico.
 The disease was subsequently reported in
many pepper growing areas in the world.
 Phytophthora blight causes yield losses up to
100% in pepper fields in Illinois.
Phytophthora Blight of Pepper
 P. capsici has a broad host range, among which
cucurbits, eggplants, and tomatoes are severely
affected in Illinois.
 It can become a serious problem during periods of
heavy rainfall; the pathogen can spread rapidly
through the crop, resulting in severe losses within
a short time.
Symptom
 Phytophthora blight affects both seedlings and nature
plants.
 Infected seedlings show typical damping-off symptoms.
Infection of older plants begins at or below the soil line.
 Water-soaked, dark brown lesions on the lower stems
(collar rot phase) usually extend upward for an inch or more
above the soil line and may expand to girdle the stems,
preventing upward movement of water and nutrients.
 This often results in a sudden wilting of foliage.
Symptom
 Root infections may also occur which kill roots
and cause wilting of the plant without the
appearance of stem cankers.
 The foliar phase of this disease commonly occurs
at forks in the branches, resulting in dark, girdling
cankers and wilting of leaves and fruits.
 Infected leaves develop circular or irregular, dark
green, water-soaked lesions which dry and appear
light tan.
Symptom
 Fruit lesions may also appear as enlarging,
watersoaked areas, which then shrivel and darken.
 A mass of white fungal growth may develop inside
the fruit, and seeds usually turn dark brown or
black.
 A fine, grayish-white to tan mold may also become
evident over the lesion on the fruit surface.
 Under humid conditions, fungal growth develops
extensively over the entire fruit.
Pathogen
 Phytophthora capsici is a soilborne pathogen.
 The pathogen produces several types of spores which
enable it to spread throughout the field, and to persist in the
field between crops.
 P. capsici survives between crops as oospores or mycelium
in infected tissue.
 An oospore is a thick-walled sexual spore.
 Oospores are resistant to desiccation, cold temperatures,
and other extreme environmental conditions, and can
survive in the soil in the absence of the host plant for many
years.
Pathogen
 Once pepper plants are transplanted into a field,
and the environmental conditions are favorable,
oospores germinate and produce sporangia and
zoospores (asexual spores).
 Rainfall,
between
soil
saturation,
24-29°C)
are
and
temperatures
necessary
developmentof Phytophthora blight.
for
Disease Cycle
 Zoospores, released in water, swim, and upon contact with
host tissue, initiate infection.
 Following infection, a girdling lesion is formed at the base
of the plant near the soil line.
 Sporangia are produced on the lesion surface and spread
by splashing rain.
 Production and spread of sporangia are repeated
throughout the season.
 Plants eventually die and oospores formed within the
lesions are released into the soil as the plant decomposes.
 Oospores will persist in the soil until another susceptible
crop is planted.
CONTROL
 A combination of methods is needed to effectively
control this disease.
 Strategies recommended for management of
Phytophthora blight of pepper include preventing
the pathogen from being moved to the field,
reduction of soil moisture, reduction of
Phytophthora spores in the soil, utilization of
resistant varieties, and applying fungicides.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：发病时期？症状特点？
• 病原：分类地位；形态特点；生物学特性
• 病害发生发展规律：越冬、传播、入侵方式
• 发病及其影响因素：气象因素（温湿度）；品种抗
病性；栽培管理
• 综合防治：选用抗病品种；农业防治；化学防治
（种子处理、及时处理中心病株）
7.2.6 Anthracnose of Pepper
• Several species of plant pathogenic fungi in the genus
Colletotrichum cause anthracnose in peppers and many
other vegetables and fruits. Until the late 1990s,
anthracnose of peppers and tomatoes was only associated
with ripe or ripening fruit.
• Since that time, a more aggressive form of the disease has
become established in Ohio and other states. This form
attacks peppers at any stage of fruit development and may
threaten the profitability of pepper crops in areas where it
becomes established. This disease can also affect tomatoes,
strawberries, and possibly other fruit and vegetable crops.
Symptom
• Circular or angular sunken lesions develop on immature
fruit of any size. Often multiple lesions form on individual
fruit.
• When disease is severe, lesions may coalesce. Often pink
to orange masses of fungal spores form in concentric rings
on the surface of the lesions . In older lesions, black
structures called acervuli may be observed. With a hand
lens, these look like small black dots; under a microscope
they look like tufts of tiny black hairs.
Symptom
• The pathogen forms spores quickly and
profusely and can spread rapidly throughout a
pepper crop, resulting in up to 100% yield loss.
Lesions may also appear on stems and leaves
as irregularly shaped brown spots with dark
brown edges .
Pathogen
• Colletotriehum nigrum
Spores of Colletotrichum released
from a fungal fruiting body (acervulus)
with numerous black, spines (setae) on pepper.
Disease Cycle
• The pathogen survives on plant debris from infected crops
and on other susceptible plant species.
• The fungus is not soil-borne for long periods in the
absence of infested plant debris.
• The fungus may also be introduced into a crop on infested
seed.
• During warm and wet periods, spores are splashed by rain
or irrigation water from diseased to healthy fruit.
• Diseased fruit act as a source of inoculum, allowing the
disease to spread from plant to plant within the field.
Disease Cycle
CONTROL
• Practice crop rotation with crops other than tomato,
eggplant, and cucurbits for at least 3 years.
• Avoid poorly drained fields for growing these crops.
• Plant the crop on a ridge, or better yet on raised,
dome-shaped beds to provide better soil drainage.
Unmulched, lowprofile beds will deteriorate during
the season and may not provide sufficient
drainage in July and August when disease spread
can occur.
CONTROL
• Maintaining the uniform soil moisture necessary to
prevent blossom end rot of peppers is difficult with
raised beds unless trickle irrigation is used.
Overhead irrigation, like rainfall, will encourage
disease spread and should be discontinued if the
disease is present.
CONTROL
• Fungicide use will vary depending upon the crop
grown and in some cases the particular disease
phase to be controlled. Refer to the current Cornell
Recommendations for Commercial Vegetable
Production for a list of available fungicides and
their proper use. Soil fumigation, although useful in
greenhouse situations, is not practical for field use
because the fungus quickly reinvades treated soil.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：发病时期？症状特点？
• 病原：分类地位；形态特点；生物学特性
• 病害发生发展规律：越冬、传播、入侵方式
• 发病及其影响因素：气象因素（温湿度）；品种抗
病性；栽培管理
• 综合防治：选用抗病品种；种子处理；加强栽培管
理；清洁果园；化学防治
7.2.7 Verticillium Wilt of eggplant
1.SIGNIFICANCE
• Verticillium wilt, caused by two species of soilborne fungi-Verticillium dahliae and Verticillium
albo-atrum, infects more than 200 species of plants,
including many vegetables.
• V. albo-atrum prefers cooler soils while V. dahliae
can become a problem in greenhouse vegetable
production. Sometimes, both species will occur in
the same field.
SYMPTOMS
• Symptoms are subtle and may be confused with
insufficient moisture or other vascular wilts.
• A yellowing of lower leaves followed by wilting is
the first sign of disease.
• Lesions have a characteristic V-shaped pattern
which is widest at the leaf margin.
• Brown, necrotic tissue within lesions is surrounded
by a large, irregular area of yellowing due to a
systemic leaf toxin produced by the fungi.
SYMPTOMS
• Because Verticillium affects the waterconducting vessels, symptoms can appear on
one side of the plant or on one side of a leaf.
• Leaf necrosis is followed by wilting, stunting, and
plant death. When the stems of infected plants
are cut lengthwise, the vascular tissue exhibits a
brown discoloration.
PATHOGEN
• Verticillium dahliae
• Verticillium albo-atrum
DISEASE CYCLE
• Verticillium species survive on infested crop
residues as microsclerotia or resistant mycelium
and in symptomless weed hosts.
• Infection generally occurs through wounds in the
roots caused by cultivation, secondary root
formation, or plant parasitic nematode feeding.
• Both species are capable of long term survival in
the soil. The disease is favored by cool weather
and neutral to alkaline soils.
CONTROL
• There is no effective chemical treatment for Verticillium Wilt,
short of soil sterilization by steam, broad spectrum
fumigants, or soil solarization.
• Practice long crop rotations with non-susceptible hosts.
Benefits of this technique are limited by the extremely wide
host range of the pathogens. Cereals or grasses should be
included in the rotation.
• Remove and destroy infested crop debris well away from
production fields.
• Control weeds in both the main crop and rotational crop, as
many weeds are also hosts for Verticillium.
小结
• 发生概况：分布？ 危害？产量损失
• 病害识别：发病时期？症状特点？
• 病原：分类地位；形态特点；生物学特性
• 病害发生发展规律：越冬、传播、入侵方式
• 发病及其影响因素：气象因素（温湿度）；品种抗
病性；栽培管理
• 综合防治：选用抗病品种；无病留种和种子处理；
加强栽培管理；化学防治