This document discusses post-harvest diseases of citrus and garlic. It provides details on 5 common citrus diseases - anthracnose, green mold, blue mold, sour rot, and Septoria spot caused by various fungi. It describes symptoms, taxonomy, and management strategies for each disease. For garlic, it covers 4 diseases - white rot, black mould rot, basal rot, and neck rot, with white rot caused by the fungus Sclerotium cepivorum discussed in detail including symptoms, epidemiology, and management approaches.

1. POST HARVEST DISEASES OF CITRUS AND
GARLIC

2. Paladiya Sharad H.
Ph. D (Scholar)
Department of Plant Pathology
N. M. College of Agriculture
NAU, Navsari.
Contact : 89800 96149

3. DISEASES OF CITRUS
1. Anthracnose (Colletotrichum gloeosporioides)
2. Green mold (Penicillium digitatum)
3. Blue mold (Penicillium italicum)
4. Sour rot (Geotrichum citri-aurantii)
5. Septoria spot (Septoria citri)

4. 1. Anthracnose
C. O. : Colletotrichum gleosporioides
 Taxonomy :
 Kingdom : Fungi
 Phylum : Ascomycota
 Class : Sordariomycetes
 Order : Glomerelles
 Family : Glomerellaceae
 Genus : Colletotrichum
 Species : C. gleosporioids

5.  Symptoms :
 Anthracnose usually only occurs on fruit that
have been injured by other agents, such as
sunburn, chemical burn, pest damage, bruising,
or extended storage periods.
 The lesions are brown to black spots of 1.5
mm or greater diameter.
 The decay is usually firm and dry but if deep
enough can soften the fruit.
 If kept under humid conditions, the spore
masses are pink to salmon, but if kept dry, the
spores appear brown to black.
 On ethylene degreed fruit, lesions are flat and
silver in color with a leathery texture. On
greened fruit, much of the rind is affected. The
lesions will eventually become brown to grey
black leading to soft rot.
 It should be noted that leaves and fruit infected
with other diseases (alternaria, citrus canker)
may also be colonized by the fruiting bodies of
C. gloeosporioides.

7.  Host Range :
 All common citrus cultivars are susceptible to anthracnose.
 Distribution :
 Anthracnose is found worldwide like Pakistan, Brazil, China, India,.
 In India, Himachal Pradesh, Tamil Nadu, Karnataka and Andhra Pradesh
etc.
 Favorable Condition :
 Cool weather (temp. 20°C) responsible for development of disease in plants
 Long period of high relative humidity >80% with mists.
 Disease cycle :
 Anthracnose is a primary colonizer of injured and senescent tissue. The
organism grows on dead wood in the canopy, and it spreads short distances
by rain splash, heavy dew, and overhead irrigation.
 Such movement deposits the spores on susceptible tissues of young leaves
or immature fruit. Sexual spores, although less numerous, are significant
for long distance dispersal because of their ability to become airborne.
 Once the spores germinate, they form a resting structure that allows them to
remain dormant until an injury occurs or until degreening.

8.  The disease is especially troublesome on fruit that are harvested early and
degreed for over 24 hours because ethylene stimulates the growth of the
fungus.

9.  Disease Management :
 Pruning of infected leaf, twigs and fruits.
 Fruit bagging at fruit stage (late Oct. – Early Nov.)
 Spray twice with carbendazim (0.1%) at 15 days interval during the
flowering to control the blossom infection.
 Spraying of Mancozeb 2g/l or Thiophanate Methyl 1g/l or
Chlorothalonil 2g/l three times at 15 days interval (Mishra et al.,
2013).
 Post harvest tratment with benzimidazole may reduce the fruit
infection.

10. 2. Green & Blue Mold
 Green Mold :
 C. O. : Penicillium digitatum
 P. digitatum is a species within
Ascomycota division of fungi.
 The genus name penicillium come
from the word penicillus which means
brush, referring to the branching
appereance of asexual reproductive
structures found within the genus.
 P. digitatus was first noted as
Aspergillus digitatus by C. H. Persoon
in 1794.

11.  Taxonomy:
 Kingdom : Fungi
 Class : Euromycetes
 Order : Eurociales
 Family : Trichocomaceae
 Genus : Penicillium
 Species : P. digitatum

12.  Symptoms :
 P. digitatum causes destructive
fruit rot of citrus. Soft water
soaked area on the peel,
followed by development of
circular colony of white mold,
up to 4 cm diameter after 24 –
36 hrs at 24oC.
 Green asexual spore (Conidia)
formed at the center of colony,
surrounded by broad band of
white mycellium.
 The lesion spread more rapidly
than those caused by P. italicum.
 The fruits rapidly spoil and
collapses (Snowdon, 1990).

13.  Epidemiology :
 P. digitatum is mesophillic fungus growing from 6 -7oC to maximum of
37oC, within an optimal growth temp. at 24oC.
 With respect to water activity P. digitatum has relatively low tolerance for
osmotic stress.
 Host Plant :
 Host plants like, grapefruits, apple, rice, plum, tomato, sorghum, grape and
maize are the major host plants.
 Ecology :
 P. digitatum is found in soil of area cultivating citrus food.
 In nature, it is often found a longiside the fruits it infects, making species
within the genus Citrus its main ecosystem.
 It is only within this species that P. digitatum complete its life cycle as
necrotroph.
 However P. digitatum has also been isolated from other food sources like
hazelnuts, kola nuts, black olives, rice, maize and meats.
 Low levels have also been noted in South – East Asian peanut, sorghums
and soybeans.

15.  Blue mold :
 C. O. : Penicillium italicum
 Taxonomy :
 Kingdom : Fungi
 Class : Euromycetes
 Order : Eurociales
 Family : Trichocomaceae
 Genus : Penicillium
 Species : P. italicum
 History :
 P. italicum the cause of citrus blue mold was described by Wehmer in 1894.
 P. italicum is a species within Ascomycota division of fungi.
 P. titalicum is the first phyto pathogenic penicillum species whose complete
genome has been entirely sequenced.

16.  Symptoms :
 P. digitatum causes destructive fruit rot
of citrus. Soft water soaked area on the
peel, followed by development of
circular colony of white mold.
 Bluish asexual spore (Conidia) formed
at the center of colony, surrounded by
broad band of white mycellium.
 The lesion spread more slowly than
those caused by P. digitatum.
 A halo of water soaked faded tissue
surround the region
 The fruits rapidly spoil and collapses.
(Brown, 1994)
 Host Plants :
 Its includes onion, garlic, citrus, sour
orange, lemon, pummelo, navel
orange, cucumber, yam and grapfruit.

17.  Management of Green & Blue mold :
 Green and blue mold initially relies on the proper handling before, during
and after harvesting.
 Spores ne be reduce by removing fallen fruits.
 Risk of injury can be decrease in many ways including storing fruit in high
humidity / low temp. conditions and harvesting before irrigation or rainfall
in order to minimize fruit susceptibility to peel damage.
 Storage at 5oC in high CO2 atmosphere reduces rot (Cheng et al., 2020).
 Inclusion of a pouch of KOH in polyethelyn wrapped fruits reduces rot
(Piga et al., 1997).
 Biological Control :
 Yeast and Bacteria have been demonstrated to have antagonistic ability
against P. digitatum and P. italicum.
 The yeat antagonistics are assumed to operate by including phytoalexins
(Yantarasri et al., 1994) or competitions for nutrients (Broby et al., 1989).
 The mechanism of biocontrol for bacillus spp. is assumed to be antibiotic
production (Yantarasri et al., 1994).
 Some strains of Pseudomonas, while being antagonistic towards P.
digitatum and P. italicum also retard wound healing in orange fruits (Haung
et al., 1991)

18.  Chemical Control :
 In the form of fungicides is also commonly used such as thibendazole and
biphenyl, all of which suppress the reproductive cycle.
 Post harvest chemical treatment usually consists of washes conducted at
40-50oC containing detergent, weak alkaline and fungicides.
 In terms of the export market, generally recognized as safe (GRAS)
substances are currently being explored as alternatives.
 GRAS substances includes sodium bicarbonate, sodium carbonate and
ethanol have displayed an ability to control P. digitatum and P. italicum by
decreasing germination rate.

19.  Taxonomy :
 Kingdom : Fungi
 Division : Ascomycota
 Class : Sachharomycetes
 Order : Sachharomycetales
 Family : Dipodaceae
 Genus : Geotrichum
 Species : G. citri
3. Sour rot
C. O. : Geotrichum citri-aurantii

20.  Symptoms:
 Tan to occasionally radish
discoloration of fruit that are starting
to rot. The fruit are turn to tan or
brown.
 Fruit flies and fruit fly larva generally
present in large numbers.
 Initial symptoms of sour rot are similar
to those of green and blue molds.
 Fungus degrades the rind, segment
walls and juicy vesicals in to slimy,
watery mass.
 At high relative humidity, the lesions
may be covered with yeasty,
sometimes wrinkled layer of white or
cream color mycellium.

21.  Epidemiology :
 Invasion of pathogen usually occurs at the point of injury of fruit.
 Pathogen commonly occurs as soil borne as is wind or splash borne to surface of
fruit within the tree canopy.
 As fruit mature, they become more susceptible to sour rot infection.
 Disease development depends on high humidity and temp. above 10oC, with
optimum being 25-30oC.
 Sour odour associated with the advanced stage and it will attract the flies, which
can disseminate the fungus and cause other injured fruit to become infected.
 Management :
 Handle your plants with great acre to reduce damage.
 Prevent damages due to bird invasion.
 Harvest prior to rainfall events can help reduce damages by sour rot.
 Use antagonistic yeats of peroxidase (POD) to control the development of sour
rot.
 For chemical control, utilize general antimicrobial such as hydrogen peroxide and
solution of potassium metabidulfite.
 Antimicrobial treatments are usually more effective when combined with
insecticide treatments against flies.

22.  Taxonomy :
 Kingdom : Fungi
 Division : Ascomycota
 Class : Dothideomycetes
 Order : Capnodiales
 Family : Mycosparallaceae
 Genus : Septoria
 Species : S. citri
4. Septoria spot
C. O : Septoria citri

23.  Symptoms:
 Early symptoms of Septoria spot appear as
small, light tan to reddish brown pit on
fruit, 1–2 mm in diameter, which usually do
not extend beyond the oil-bearing tissue.
 Advanced lesions are blackish, sunken,
extend into the albedo (white spongy inner
part of rind), and are up to 20–30 mm in
diameter.
 Dark brown to black fruiting bodies often
develop in these lesions, which usually do
not extend beyond the oil-bearing tissue.
 The spots are much more conspicuous after
the fruit has changed from green to yellow
or orange.
 Small spots may develop into large, brown
blotches during storage or long-distance
transportation.
 Septoria citri may also cause similar
spotting on leaves or twigs that are
weakened by frost or pests.

24.  Epidemiology :
 The fungus survives on infected twigs, in dead wood and leaves and in the
leaf litter.
 Spores are spread to healthy leaves and fruit by splashing water.
 Infection occurs when the fruit is still green in late summer or autumn after
cool, damp weather.
 The fungus remains dormant in the fruit until symptoms develop 5–6
months later as the fruit ripens, usually following a period of cold windy
weather.
 Septoria spot is generally more severe during years of higher than normal
rainfall.
 Low or rapidly changing temperatures are thought to predispose citrus
tissue to the disease
 Management :
 Control is achieved by applying copper fungicides in mid-february to early
March prior to autumn rainfall (Donovan, 2007).
 Other management practices that may be used to reduce disease levels
include tree skirting to improve air circulation, avoiding the use of
overhead irrigation, harvesting fruit early and the removal and destruction
of fallen leaves and fruit.
 Practices that promote good tree health and vigour will also reduce the
economic impact of the disease in the orchard.

25. Diseases of Garlic
1. White rot (Sclerotium cepivorum)
2. Black mould rot (Aspergillus niger)
3. Basal rot (Fusarium oxysporum f. sp. cepae)
4. Neck rot (Botrytis allii)

26. 1. White rot
C. O. : Sclerotium cepivorum
 Taxonomy :
 Kingdom : Fungi
 Phylum : Ascomycota
 Class : Ascomycetes
 Order : Helotiales
 Family : Sclerotiniaceae
 Genus : Sclerotium
 Species : S. cepivorum

27.  Symptoms :
 Leaves of plants infected with the white
rot pathogen show yellowing, leaf
dieback, and wilting. Leaf decay begins
at the base, with older leaves being the
first to collapse. This results in a semi-
watery decay of the bulb scales.
 Roots also rot, and as a result, the plant
can be pulled from the ground easily.
 At early stages of disease development, a
fluffy white growth (the fungal
mycelium) is associated with the rot,
which develops around the base of the
bulb.
 As the disease progresses, the mycelium
becomes more compacted and less
conspicuous, with numerous small,
spherical black bodies (sclerotia)
forming on this mycelial mat. These
sclerotia are the resting bodies of the
pathogen and are approximately the size
of a pin head or poppy seed.

28.  Epidemiology :
 S. cepivorum, a fungus, enough sclerotia from an initially high population may
survive 20 to 30 years or more in soil without the presence of an Allium host.
 Only Allium spp. such as onion, leek, and shallot are attacked.
 Sclerotia can infect plants from 12 inches below the surface. One sclerotium can
infect a group of 20 to 30 adjacent plants.
 Fungal activity is favored by cool soils and is restricted above 75°F. Once the
disease is in a field, it is very difficult to grow Allium spp. successfully.

29.  Management :
 Use resistant varieties
 Use only clean stock from known origins that have no history of
white rot.
 Wash equipment before entering a field to avoid moving soil
contaminated with sclerotia into new fields.
 Hot water seed treatment kills sclerotia on clove surfaces (Mishra et
al., 2013) but will not destroy all fungus within cloves.
 If practical, dig out all plants in infested spots in the field. Also
remove healthy plants next to diseased plants. Remove some soil
with both diseased and healthy plants.
 In addition, follow a long-term rotation schedule, and do not follow
Allium crops with other Allium crops.
 If the disease is observed, ceasing irrigation will minimize damage
 Ensure a good drainage to avoid water logging as a spread
mechanism.
 Avoid excessive fertilizer with nitrogen.

30.  Species like Trichoderma, Fusarium, Chaetomium etc. are very effective
parasite of white rot causing fungus.
 Seed treatment with Thiram (2 g/kg of seed) and soil application of
Carbendazim, Thiophanate Methyl (Topsin-M) or Benomyl at 0.1% is
effective in the controlling the disease (Mishra et al., 2014).
 Seedling dip in Carbendazim (0.1%) or with antagonist viz. Pseudomonas
cepacia, and Trichoderma viride significantly reduces the basal rot in onion
crop (Mishra et al., 2014).
 Dilbo et al. (2015) conducted an experiment to control the white rot disease
with the objective of evaluating the effect of two fungicides (Apron Star 42
WS and Tebuconazole) and in combination with four Trichoderma species
namely T. hamatum, T. harzianum, T. oblongisporum and T. viride. The
results of this study revealed that the efficacy of both fungicides, when
tested alone, against S. cepivorum was lower than those treated with
Trichoderma spp. alone and the fungicide combined treatments. Among all
treatments, T16 (Apron Star 42 WS fungicide combined with T. hamatum
and T. viride)has provided the best antagonistic activity against S.
cepivorum with no disease incidence,

31. 2. Black mould rot
C. O. : Aspergillus niger
 Taxonomy:
 Kingdom : Fungi
 Phylum : Ascomycota
 Class : Eurotiomycetes
 Order : Eurotiales
 Family : Trichomaceae
 Genus : Aspergillus
 Species : A. niger

32.  Symptoms :
 Infected bulbs are discolored black around the neck, and affected scales shrivel.
 Masses of powdery black spores generally are arranged as streaks along veins on and
between outer dry scales.
 Infection may advance from the neck into the central fleshy scales. In advanced disease
stages, the entire bulb surface turns black, and secondary bacterial soft rot may make the
bulb soft and mushy.
 No external symptoms may be found with some bulbs.
 Under dry conditions, diseased scales dry and shrivel, and black masses of spores are
visible between outer scales. Affected parts may also be invaded by soft rot bacteria,
causing the whole bulb to deteriorate into a watery soft rot (Anonymous, 2012).

33.  Disease Cycle :
 Aspergillus niger is a soil borne as well as wind borne fungus
that can survive on plant debris in the soil.
 Infections spread from bulb to bulb by direct contact, through
bruises or wounds, by mechanical means or by air-borne
spores.
 Spores can germinate within three to six hours under high
relative humidity, but germination is inhibited below 75 per
cent relative humidity.
 The optimum temperature for growth of A. niger ranges from
28 to 34 °C, and it is inhibited below 17 and above 47 °C
(Sumner, 1995).
 Sporulation can take place in 24 h after infection (Ko et al.,
2002).

35.  Management :
 Selection of healthy bulbs for planting is best remedy to minimize
the occurrence of the black mould rot disease.
 Crop rotation should be followed for 3 to 4 years with other than
garlic and leek crops.
 Soil solarization: Covering of soil surface with 100 gauge LLDPE
transparent plastic film for 15 days in the hot summer season after
giving light irrigation in the soil is effective (Prajapati & Patil,
2015).
 Deep ploughing of soil in hot summer season helps to kill the
pathogens present in the soil with direct exposure to high
temperature, thus infection of bulbs can be minimized.
 Do not apply nitrogen 4–5 weeks before harvest. Nitrogen
stimulates growth of soil fungi and makes the onion tissues
susceptible to infections (Anonymous, 2009).
 Application of carbendazim @ 0.1% concentration found most
effective against black mould rot when applied either as foliar spray
in standing crop of onion or as a post –harvest dip, followed by
mancozeb (0.25%) (Srivinasan et al. 2006).

36.  Pre-harvest application of carbendazim + mancozeb at 0.2 per cent
found most effective against black mould rot (Ahir and Maharshi,
2008).
 Cares at harvesting:
 Do not clip tops too close to the bulb. Tops should be cut 1/2 to 3/4
inch from the bulb to allow proper drying and sealing of the neck.
 Follow good sanitation in the field and packing shed. Remove
diseased, bruised or sunburned bulbs during harvest, grading and
packing to avoid contamination of entire lots.
 Minimize mechanical damage.
 Keep bulbs dry and practice through curing. This is essential after
harvest; wet or improperly cured onions are highly susceptible to
fungal rots.
 The best storage temperature is 0–2°C (32–35°F); the best relative
humidity is 65-70 per cent (Mishra et al., 2013).

37. 3. Basal rot
C. O. : Fusarium oxysporum f. sp. cepae
 Taxonomy:
 Kingdom : Fungi
 Phylum : Ascomycota
 Class : Sordariomycetes
 Order : Hypocreales
 Genus : Fusarium
 Species : F. oxysporum

38.  Symptoms :
 Plants may or may not show symptoms in the field or at harvest, but bulbs may
subsequently rot in storage.
 In the field affected plants may show reduced emergence, yellowing or browning
(necrosis) of leaves beginning at tips. The discoloration will move toward the base of the
leaf, which will eventually wither and die.
 In storage, bulbs show spongy, sunken, yellow-brown rotting lesions. In the early stages,
infected bulbs are softened, brown and watery when cut open.
 There may be a white, light pink or reddish fungal growth (mycelium) covering the
cloves, or in the rot cavities. Deep cracks form in the cloves, followed by breakdown of
the tissue, which will eventually dry down to a portion of its original size, the cloves
becoming crinkled and small.

39.  Disease cycle :
 Fusarium is a soil-borne fungus and can persist for long periods in the soil.
 Transmission may occur via infested soil on tools or equipment, infected
debris, infected seed, or run-off water. The pathogen enters the plant
through stem plate or wounded tissue.
 The disease develops from the base of the bulb and progresses towards the
tips of the cloves.
 Infection may occur at any time in the field, or in storage. The disease is
favored by higher temp. 20-30o
C and high humidity. Late season rains may
favor the pathogen.
 Host Plants :
 Onion
 Garlic
 Leek
 Shallot
 Management :
 Inspect all bulbs at harvest and discard any bulbs with symptoms of rot.
 Store bulbs at 0℃ and relative humidity of 65-70%. Inspect stored onions
and garlic regularly and discard any infected bulbs.

40.  Avoid rotations with Allium spp. (e.g. onions, shallots, bunching onions,
chives, and leeks) and cereals, on which this fungus can also cause disease.
 Store bulb sat cool temperatures and low humidity with good ventilation.
 Avoid storing damaged bulbs.
 Hot water treatment of symptomless, infected cloves may be useful only if
incidence is low.
 Application of bio-control agent like T. viride, T. harzianum etc. as soil
application or seed or seeding treatment for control of this disease.
 Seed treatment with Thiram (2 g/kg of seed) and soil application of
Carbendazim, Thiophanate Methyl (Topsin-M) or Benomyl at 0.1% is
effective in the controlling the disease (Mishra et al., 2014).
 Behrani et al. (2015) evaluated four fungicides i.e. Antracol, Carbendazim,
Copper oxychloride and Kingmil MZ with 10, 100, 1000 and 10000 ppm
concentrations against F. oxysporum (Basal rot of garlic) under in-vitro as
well as in-vivo conditions and revealed that among four fungicides,
Carbendazim followed by Antracol appeared as the most effective
fungicides.

41. 4. Neck rot
C. O. : Botrytis allii
 Taxonomy :
 Kingdom : Fungi
 Phylum : Ascomycota
 Class : Leotiomycetes
 Order : Helotiales
 Genus : Botrytis
 Species : B. allii

42.  Symptoms :
 The disease usually appears first on necks near the soil line at any time after spring.
The disease becomes worse when it starts early in the season.
 Extensive development of sclerotia is best seen on maturing bulbs just before and
during harvest.
 The fungus moves rapidly into the succulent garlic bulb's neck region, producing a
water-soaked appearance.
 A gray mold develops on the surface of or between garlic scales, later producing black
bodies (sclerotia), which develop around the neck.
 Before bulbing, plants may die or recover if weather permits. Bulbs infected late break
down to a soft mass, and secondary infections by other organisms follow.

43.  Disease cycle :
 Botrytis allii overwinters in the soil on bulb residue or as sclerotia.
 In the spring, sclerotia germinate and directly infect bulbs or produce
asexual spores, which are dispersed in the air.
 Spores and sclerotia that come in contact with tissue of susceptible hosts
may initiate new infections, especially if the tissue is wounded.
 Under prolonged moist conditions, the pathogen can also produce spores on
infected dead or dying leaves.
 After harvest, topped onions and garlic can become infected if the cut edge
comes in contact with spores or soil containing sclerotia.
 Often, plants will become infected in the field but will remain symptomless
until they are in storage.
 Host Plant :
 Garlic
 Onion
 Management :
 Use disease free cloves.
 Avoid frequent and excessive irrigation.
 Inspect garlic for symptoms and signs of the disease during the season and
at harvest. A hand lens can help with this.

44.  Allow the tops to mature well, then lift or undercut the garlic
(Mishra et al., 2014).
 If dry weather prevails, cure garlic on the ground for 6-10 days.
 When topping, minimize bruising and mechanical injury.
 Store cured garlic in a well-ventilated area at temperatures of 32°F,
or just slightly higher.

45. “You learn more from failure than from
success. Don’t let it stop you. Failure
builds character.”
Thankyou…