Fungus

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LIST OF DISEASES
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14.
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
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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
.
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
•
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)
•
Leaves, stems and fruits are attacked
•
Brown to purple black lesions – leaflet, stem, fruit
•
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)
•
•
•
•
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)



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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


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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

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