2015021026 citrus scab

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.