Transcript Fungus
LIST OF DISEASES
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Gray Mould
- Botrytis cinerea
Rhizopus rot
- R. stolanifer
Sour-rot
- Geotrichum candidum
Canker
- Didymella lycopersici
Anthracnose
-C.coccodes, C. gloeosporoides
Bacterial Canker
-Clavibacter michiganense subsp.
michiganense
Buckeye Rot
-Phytophthora nicotianae var. parasitica
Fusarium rot
-Fusarium oxysporum f.sp. lycopersici
Phoma Rot
-Phoma destructiva
Soil Rot
-Rhizoctonia solani
Southern Blight
-Sclerotium rolfsii
Early Blight
-Alternaria solani
Bacterial Soft Rot –Erwinia caratovora sub sp. carotovora
Late Blight
-Phytophthora infestans
GRAY MOULD (BOTRYTIS CINEREA)
Symptoms
Watery lesion area with a light brown or tan-colored central region
which contain dark-brown specks
Converted into a soft, watery mass within a few days
Skin is broken, the grayish mycelium and spore clusters develop
within a few hours
Fungus
Greek botrys, meaning a bunch of grapes
One-celled spores are borne on branched conidiophores
Sclerotia -measure up to 3 mm - smaller & thinner
Germinate to produce conidiophores or, rarely, give rise to small cup-shaped
structures (apothecia)
Favourable condition
Optimum RH for spore production is about 90%
Spores are produced during the night when the temperature is lower and the
RH is higher than during the day.
Ideal Temperatures of 17–23 °C
The length of the surface wetness period needs to be longer at the lower
temperatures for disease development
Spread and survival
Botrytis produces sclerotia which survive in soil, dead plant material, or on
different host plants
Easily disperse large distances by wind & shorter distances by splashing and
windblown rain
Fruit can be infected through the stem scar, growth cracks, or other breaks in
the skin
Plants approaching maturity are more susceptible
Control
Ensure good drainage facility
In the greenhouse, maintain a RH of less than 80%, during the night
Remove decaying plant material from the plant bed
Avoid bruising during packing and transport
Pre harvest spray 0.2% captan at monthly intervals
RHIZOPUS ROT- R. STOLANIFER
Water-soaked lesion which exude a clear liquid
Lesion surface may be covered with thin, cotton-like fungal structures
(especially under humid conditions)
Tissues within the lesion are usually held together by relatively coarse
strands of fungal hyphae
Dark sporulation may crown the white tuft of Rhizopus
The mycelium can infect adjacent fruit through natural openings or
mechanical wounds, creating nests of mold and diseased fruit
Penetration:
Wound - cause ripe fruit to rot-Fermentative odour
Fruit surf. –extramatrical whiskery mycelium , black sporangia
Range of temp. 5, 15 and 25oC reaching disease incidence of
97-100% RH
Spread
Air currents
pathogen grows very aggressively even on refrigerated fruit.
pallets and cartons, and it may survive for months in fruit
residues left in picking containers and field bins.
ANTHRACNOSE (COLLETOTRICHUM COCCODES,
C. GLOEOSPOROIDES, C. DEMATIUM)
Symptoms
Symptoms - fruits which are ripe or beginning to ripe
Small, water soaked, circular & depressed spots -enlarge to greater than
12 mm in dia with zonate markings
Lesion surface may appear salmon-colored due to spore production and
be dotted with black specks (microsclerotia)
Favorable condition
Opt temp- 28 to 32oC
Remain latent in green fruits until fruits approach ripening stage
RH-85-to100%
Fungus
Colonies - darkly pigmented with white aerial mycelium, consisting of
numerous black sclerotia
Sclerotia - setose, spherical
Conidia - straight, fusiform, attenuated at the ends
Appressoria - clavate, brown, variable in shape
Conidia of C. coccodes
Appressoria of C. coccodes
Mode of survival and spread
Persist on alternate hosts, crop debris & some weeds
Alternate hosts - solanaceous crops (potato, eggplant),cucurbits & soybean
Fungus is also seed-borne
Spores are usually dispersed by splashing rain
Fruits - near the soil surface are most likely to become infected
Overhead irrigation - favor development of anthracnose because of RH &
increased duration of leaf wetness
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Control
Crop rotation with non-host crops and avoid potato, soybean, eggplant &
cucurbit
Stake plants to improve air circulation and to reduce leaf and fruit wetness
Mulch to reduce soil splash onto fruit and lower leaves
Minimize or avoid overhead irrigation to reduce periods of wetness on fruit
Hot water treatment - at 50°C for 25 min
Following treatment, plunge the hot seeds into cold water, dry on paper, and
dust with thiram
EARLY BLIGHT (ALTERNARIA SOLANI)
Symptoms
• Leaves – circular to angular, dark brown to black spots with
characteristic concentric rings
• Spots coalesce and cause drying of leaves
• Stem- dark spots at base near the ground and gradually girdled
• Spots- juncture of the side branches- easily broken by wind
• Fruit become infected-through the calyx or stem attachment, either in
the green or ripe stage
• Fruit –dark brown sunken, concentric ringing
• Infected fruit frequently drop, and losses of 50% of the immature fruit
may occur
Fungus
Mycelium- septate, branched, light brown, become darker with age
Conidiophores- 50 to 90μm in length and dark coloured
Conidia-beaked, muriform, dark coloured and borne singly
Epidimiology
Maximum dispersal of conidia- 9am and 12 noon
plants suffering from water stress- susceptible
Mode of spread and survival
Spread by wind and rain splashes
Under dry conditions- survives in infected plant debris in the soil for
3 yrs
Seed borne
Control
Use disease free seeds for sowing
Field sanitation
Crop rotation with non solanaceous crop
Optimum irrigation- to avoid stress condition
Seed treatment- thiram 2g/kg
3 sprays with difolatan 0.2 % at fortnightly interval
BACTERIAL SOFT ROT AND HOLLOW STEM
(ERWINIA CAROTOVORA PV. CAROTOVORA)
Symptoms
• Inner stem - which becomes brown and slimy, then
disintegrates & becomes hollow
• The affected plants wilt and die
• Fruit -soft watery decay of fruit, starting at one or more
points, as very small spots
• Enlarge-very rapidly until the entire fruit -soft watery
mass
• Pathogen liquefies fruit tissue by breaking down the
pectate "glue" that holds plant cells together
Bacteria
gram-ve, rod with rounded ends
Motile with 1 to 6 peritrichous flagella
Single-celled - rapidly multiply and spread-in water.
Favorable Conditions
During wet weather and High humidity,
Heavy rain fall or irrigation
Warm temperatures in the (20–30 °C)
Penetration
Wounds
The connective tissue at the stem end - an entry point for
the bacteria present in the sepals of young tomato fruit
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Pathogen Spread
They can be spread by rainstorms, insects, harvest crews, picking
containers, and packinghouse equipment.
Soft rot bacteria can even pass from one fiberboard shipping carton
to an adjacent carton when the cartons become soaked with the
rotten material of decayed fruit.
These bacteria readily disperse from rotten fruit by direct contact or
movement of juices or water
Management
Prevent the occurrence of insect wounds by controlling the pests
Crop rotation with crops of bean, maize and soybean
Disinfect hands and tools when pruning tomato plants and wash
contaminated clothing
Use chlorinated water to reduce the risk of infection during washing.
This will not reduce soft rot development in fruit already infected
with the organism
Harvest during dry weather and minimize fruit injury at harvest
LATE BLIGHT
(PHYTOPHTHORA INFESTANS)
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Leaves, stems and fruits are attacked
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Brown to purple black lesions – leaflet, stem, fruit
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Early russet brown marbled areas appear on the green fruits
which becomes completely brown & shriveled
Fungus
Mycelium- hyaline and coenocytic
Sporangiospore – slender, hyaline, thick walled and branched
Sporangia – multinucleate, thin walled, hyaline
Sporangia- wind borne, germinate usually by formation of
zoospores, which are biflagellate
Mode of spread & survival
Survival - diseased crop debris under wet condition
Very moist weather- white weft of fungus develops in fruit cracks
Epidemiology
Develops quickly in rainy season
High humidity condition
Control
Field sanitation
Avoid overhead irrigation
Effective control of blight in foliages
Spraying @ 7 days interval- mancozeb 0.2 %,Zineb 0.2%
PHOMA ROT
(PHOMA DESTRUCTIVA)
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Leaves- small, dark, irregular spots – yellow and wither
prematurely
Fruits- circular, depressed water soaked spots
Become black an leathery on the surface bearing numerous
black specks
specks - pycnidia or fruiting bodies of the fungus
Fungus
• Mycelium- septate, branching & hyaline, becoming dark
with age
• Pycnidia – subcutaneous and later erumpent, dark
subglobose
• Pycnospores- hyaline, subglobous
pycnidia in the lesion center
Favorable Conditions
moderate temperature and high humidity.
Most rapid decay on ripe fruits @ 21oC, but since tomatoes ripen
more rapidly at about 23oC, the disease may be more promptly in
the ripening room
Pathogen spread
Seed borne
By infected transplants or rain-splashed from infected crop debris
Fruits – wounds, stem scars
Progress is more in ripe than in green fruits
Control
Seed treatment – ceresan dust (5% ethyl mercury phosphate)
Seed be sanitation
Do not harvest when plants are wet
To ctrl contamination in packing process- 5% borax solution
containing 0.5 % liquid tar soap as washing medium
SOIL ROT (RHIZOCTONIA SOLANI)
This fungus causes the fruit to decay in all stages of
development
penetrates the fruit through wounds or the unbroken
epidermis and invades the tissue,
causing numerous small, brown, sunken spots on the side of
the fruit that is in contact with the soil.
Usually there is a single point of invasion by the fungus,
and as this spot enlarges it becomes zonate with concentric
brown rings, somewhat typical of buckeye rot.. With this
disease, the zoning is extremely definite and more
pronounced.
In most cases, the epidermis is ruptured at the center of
the spot in soil rot,
The buff to brown mycelium of the fungus
may be evident where the epidermis has
ruptured
Pathogen spread
soilborne and rain-splashed.
Favorable conditions
wet, moderately warm (75-80 F.) weather
Controls
Trichoderma harzianum, when to added to soil or applied as a
coating on tomato fruits, at a con. of 109 conidia /ml. provided
significant control of fruit rot caused by R. solani and the
secondary bacterial invader causing soft rot.
This disease is seldom of importance in fields where the plants
are staked, pruned and/or grown on plastic mulch.
Fruit losses in transit can be controlled by careful grading.
SOUTHERN BLIGHT
(SCLEROTIUM ROLFSII)
Mature plants are attacked just below the soil surface and are
completely girdled
The tops wilt and die rapidly
Mycelium often grows over the diseased tissue and
surrounding soil forming a white mat of mycelial threads with
the typical tan-to brown, at the crown mustard-seed-sized
sclerotia
Often the entire root system is destroyed
Southern Blight
Fungus is exceedingly destructive on ground crops and attacks the
fruit where they contact the soil.
Slightly sunken, yellow spots develop on invaded fruit, which rapidly
decay, collapse, and become covered by a white fungal mass with
numerous sclerotia.
Pathogen spread
Soil borne, machinery or water-moved infested soil, survives on
numerous weed and crop hosts
Favorable Conditions
wet periods of high temperatures (85-95 F.)
BACTERIAL CANKER
(CLAVIBACTER MICHIGANENSE SUBSP. MICHIGANENSE)
Leaves: general chlorosis, drying & wilting
Stem, Shoots & petiole – long, brownish stripes
Pith- creamy white, yellow or reddish brown discoloration
of cavities & exude bacteria
Fruit: Birds eye spot (Small, round white raised spots)
Later –light brown roughened centre surrounded by white halo
Brown lesion on stem and
vascular discolouration
Wilting and necrosis &
death of lower leaves
Bird's-eye" like spots on fruit
Bacterium
G+ve, non-motile, 0.7x0.6μm, produce capsules in culture.
Mode of spread and survival
Seed borne, diseased pl. debris,
Survival in Soil-1 to 4 years.
Enters through wounds-stem or roots
Caused by rain splashes or overhead irrigation
Epidimiology
Air & soil temp. 100c to 360c. Opt. temp. 280c
Survives in solanaceous weed
Control
Field sanitation
Crop rotation – 3 yrs
Seed treatment- chemical or hot water treatment
2 to 4 sprays of streptomycin to the bed followed by weekly field
field sprays of copper sulphate 53 %
BUCKEYE ROT
PHYTOPHTHORA
NICOTIANAE VAR. PARASITICA
Symptoms
Brownish, circular spots – immature green spots at blossom end
lesion- concentric rings, dark brown and light brown bands
Severe stage- internal rotted tissue is semi watery, external retains brown,
firm consistency with no extramatrical mycelium unless the surface is
ruptured
Pathogen
Hyphae – 9μm wide
Sporangiospores – thinner than vegetative hyphae, irregularly branched
Sporangia – papillate, ellisoid to spherical
Antheridia- amphigynous
Yellowish brown oogonia
Mode of spread and survival
Survives in soil in the form of resting spores from one season to
another
Pathogen- soil borne and internally seed borne
Spreads by splash transmission of soil
When fruits come in contact with the ground
Epidemiology
Common in poorly drained fields
High humidity & rainfall
Disease appears within 4 days at 22.5oC
Management
Good drainage facility
Remove Lower leaves and fruits – to avoid soil contact
Staking of plants
Mulching with some straw
Soil sterilization with chloropicrin
Weekly spray- 0.2 % captafol
Better result – combination of mulching and 0.3 % difolatan spray
FUSARIUM ROT
(F. O F. SP. LYCOPERSICI RACES 1-3)
Yellowing of lower leaves in initial stage & discolouration of younger
leaves soon follows
Leaves-droop, wilt and die
Vascular tissue of a diseased plant is dark brown in color
Fruit infection occasionally occurs and can be detected by the
vascular tissue discoloration within the fruit
Fruits ripen prematurely
Fungus
Mycelium-septate, hyaline at first becoming cream coloured with
age
Microconidia- one celled, hyaline, ovoid to ellipsoid
Mode of spread and survival
Soil borne and seed borne
Soil-survive as chlamydospores or as saprophytically growing
mycelium in infected crop debris for more than 10 yrs
Spread by seedlings raised in infected soil
Wind borne spores, surface water and agricultural implementsfield to field spread
Epidemiology
Alternating low and high soil temperature and high humidity
Opt. temperature- 28oC
Other favorable factors- light sandy soil, low soil moisture and ph
Control
Remove infected plant debris an destroy
Seed treatment- carbendazim 2g/kg
SOUR-ROT
GEOTRICHUM CANDIDUM
Growth on lesions on fruit resembles a thick, gelatinous mass
similar in appearance to cottage cheese.
Lesions themselves may initially be relatively firm as in
pickled tomatoes, but later the tissues break down much
like bacterial soft rot.
Odor of these lesions is similar to that produced by lactic acid
bacteria, hence the disease name, sour rot.
Max. disease incidence -25OC
CANKER
DIDYMELLA
LYCOPERSICI
Stem – lesions near the ground
Cankers may girdle the stem and wilting follows
Fruit – rotting, lesions at stem end
Fungus
Perithecia-subglobose, asci- cylindrical
Ascospores – spindle shaped, hyaline, uniseptate
Pycnidia- 100 to 270μ; pycnospores- unicellular, hyaline
Spread & Survival
Penetrates - wounds and stomata
Survives on plant debris in the soil and spreads from the infected
lesions on the collar and the stem through the tools handled in cutting
and land works, air draught and water splash.
Dissemination occurs mainly through conidia (produced by the
pycnidia) and not through ascospores
Rarely seed-borne
Favourable condition
Optimum temperature - 19 - 20°C.
Its outbreak is more severe in heavy moist land and in crops sown in
cold soil.
Control
Seed treatment
Field sanitation
Soil treatment- formaldehyde