Major disease in Citrus crop. Tangerine cultivar is highly susceptible. Symptoms appear on twigs,petioles,leaves and on fruits.

1. COLLEGE OF AGRICULTURAL TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University, Coimbatore-3)
Kullapuram (Po), Via Vaigai Dam, Theni-625 562
CITRUS SCAB / VERUCOSIS
Student: Course Teacher:
P. Deepa Gnana Sundari Dr. Parthasarathy .S
2015021026 Asst. Prof., Plant Pathology.

2. Citrus Scab
Other Names :
India – Sour Orange Scab / Common Scab
– Elsinoe fawcetti
South America – Sweet Orange fruit Scab
- Elsinoe australis
Australia and
Newzealand – Australian Scab
– Sphaceloma fawcetti var. scabiosa

3. Distribution in World
• Asia
• Africa
• North, South, and Central America
• Europe
• Australia
• New Guinea
• New Zealand

4. Distribution in India
• Punjab
• Assam,
• Karnataka
• Uttar Pradesh
• Andhra Pradesh.h
All the Citrus growing regions in India.

5. Pathogen and its characters
• The fungal pathogen is Elsinoe fawcetti ( (Bittancourt
& Jenkins.) 1936)
Teleomorph or Sexual stage of the pathogen
is Sphaceloma fawcetti ( (Jenkins.) 1936)
• Elsinoe australis ( ( Bittancourt & Jenkins.) 1936)

6. Pathogens
•A and B – Hyaline conidia
of Elsinoe fawcetti and
Elsinoe australis
•C – Hyaline conidia on leaf
lesion of Elsinoe fawcetti
observed under Scanning
Electron Microscope
•D – Spindle-shaped conidia
of Elsinoe fawcetti produced
on leaf lesion

7. Elsinoe fawcetti and Elsinoe australis
• Elsinoe fawcetti – 5 -6 µm × 4-8 µm produces smaller
ascospores, produces single – celled , hyaline, elliptical
conidia with sizes of 3-4 µm × 4-8 µm . Also produces
dark-pigmented and spindle-shaped conidia on scab
lesions.
• Elsinoe australis does not produce spindle-shaped conidia.

8. Systematic Position – Elsinoe fawcetti
Kingdom : Fungi
Phylum : Ascomycota
Class : Dothideomycetes
Subclass : Dothideomycetidae
Order : Myriangiales
Family : Elsinoaceae
Genus : Elsinoe
Species : E. fawcetti

9. Systematic Position – Elsinoe australis
Kingdom : Fungi
Phylum : Ascomycota
Class : Dothideomycetes
Subclass : Dothideomycetidae
Order : Myriangiales
Family : Elsinoaceae
Genus : Elsinoe
Species : E. australis

10. Life Cycle

11.  Fungal spores are readily produced on the surface
of scab lesions on young fruits and leaves throughout
the year. The Rough lemon and Rangpurlime
rootstock are also highly susceptible to scab and can
act as a source of inoculums.
 Spores of the fungus are spread in the orchard by
rain, overhead irrigation and spraying drift.

12.  Dew may also cause the spores tobe liberated from
the lesions but due to the limited splashing action,
there would only be localised dispersal. Some dry
spores can also be spread by winds in excess of 2 m/s

13. Mode of Spread
• The fungus survives the off-season as ascospores
• The secondary spread is through air borne conidia

14. Epidemology
• Young leaves are highly susceptible.
• The fungus infects tissues only when the surface is wet and
prefers temperature of 16 to 23ºC.
• The disease is a problem under low temperature and high
humidity conditions.

15. Symptoms
On Twigs, petioles or newly emerging shoot apices
 It may cause distortion on highly susceptible citrus
cultivars (i.e., some tangerines). Pustules develop on
the invaded side of young leaves, producing
corresponding depressions on the non-invaded side of
leaves.
 Light brown, raised, circular scabs appear on young
stems or green twigs.

16. On Leaves
• Scab on tangerine fruits, leaves
and stem

17. Early Stage Advanced stage

18. Upper Surface Lower surface

19. Conial deformations on the
leaf
Close up of scabby areas at the
tip

20. On Leaves
• Light brown pustules or scabs develop on leaves, and
are sometimes visible on both upper and lower
surfaces.
• Leaves are more susceptible to pustules when they
are young, and develop some resistance to scab with
age.
• The scabs consist of the body of the fungus, or
stroma, plus swollen, hyperplastic host tissues.

21. On Fruits
 When the pathogen infects young fruits, light brown,
raised, rounded, warty scabs appear on the rind surface.
 Extensive scabby areas may form as individual pustules
merge into each other.
 Note on color of scabs: Scab color may range from pink
to light brown after infection and from grey to black later
in the season.

22. On fruits
Pustules on the fruit
Scab on a ripening rough lemon
fruit

23. Integrated Disease Management
Cultural control
• Crop sanitation, establishing citrus nurseries in dry
areas or in greenhouses, and adoption of proper
treatments, may help in production of rootstocks and
budwood free from the pathogen.
• Collect the infected leaves and burn it.

24. Reaction of some Citrus Species to
Scab
Reaction Species / Varieties
Highly Susceptible Rough lemon, Adajamir, Lime, Karna,
Citron
Moderately Susceptible Florida rough, Citrus jambhiri (Italian –
76), Jambhiri brown
Resistant Sweet lime, Kagzi lime, Lemon, Genoa,
Lemon seedless, Turanj, Sweet orange
and Mandarins
Immune ( symptoms never seen) Kumquats, Khasi mandarin and Poncirus
trifoliata

25. Weed control
• Do not allow tall weeds to grow around citrus plants
as they increase the relative humidity in the citrus tree
canopy.
• High relative humidity favors infection and disease
development.

26. Chemical Method
• Several fungicides such as thiophanate methyl,
azoxystrobin, trifloxystrobin, pyraclostrobin, ferbam, and
copper fungicides can be used for control of citrus scab.
• The disease was effectively controlled by spraying
Macuprax (0.3%) or Burcop (0.3%). The fungicides left a
longer residual effect for 30-40 days on the foliage and
enabled a reduction in the frequency of sprays.

27. • Two sprays of hexaconozole (0.01%) + streptomycine
sulphate (100 ppm) one at one month after fruit set
and second at one month after first spray reduces scab
incidence effectively under south Indian conditions.
Chemicals and bio agents are reported to be effective
against citrus scab

28. Biological Control
• Allamanda leaf extract was noted as most
effective material followed by carbendazim
50%WP, propiconazole, Cupravit 50 WP and
mancozeb . Trees need to be regularly pruned
to keep them open and free of deadwood

29. References
• Thind, T.S., Diseases of Fruits and Vegetables and their
Management, Kalyani publishers, 2001,P.No. 71-72.
• www.lsuagcenter.com.
• Amrik Singh Sidhu, Climate resilient fruit production with reference
to citrus, National Citrus Meet, NRCC, Nagpur, India. 2013 August
12-13; p: 233-241.
• Shyam Singh, Srivastava AK and Shivankar VJ. Citrus based
cropping system - A review. Agric Rev. 1999; 20(2): 123-28.