Diseases of colocasia / Taro

1. DISEASES OF COLACASIA
(Taro / Cocoyam)
STUDENT COURSE TEACHER
Syed Mohamed Ibrahim.S Dr. S. Parthasarathy
ID.No: 2015021131 Asst. Prof. (Plant Pathology)

2. Disease Name Pathogen Name
Phytophthora leaf blight Phytophthora colacasiae
Pythium rot Pythium aphanidermatum
Corm rot Phytophthora nicotianae var.
parasitica
Soft rot Erwinia carotovora sub sp.
caratovora
Mosaic disease Dasheen mosaic virus

3. Disease Name
Phytophthora leaf blight
Pathogen Name
Phytophthora colacasiae

4. Systematic position
Kingdom : Fungi
Phylum : Oomycota
Class : Oomycetes
Order : Peronosporales
Family : Peronosporaceae
Genus : Phytophthora
Species : colacasiae

5. Pathogen description
• It produces coenocytic mycelium with
sporangiophore.
• The sporangiophore produces the papillate sporangia
which contains zoospores.

6. Survival and spread
• Primary spread – oospores, dormant mycelium in
plant debris.
• Secondary spread through zoospores.

7. Symptoms
• Early stages – small circular water soaked lessions,
generally dark brown or purple.
• Lesion produces clear amber fluid exudates.
• Later, the fluid changes into light yellow to dark
purple colour then rapidly enlarges and covered the
entire area and collapsed.

8. © common. Wikipedia. org

9. Management
Cultural Methods
• Increases the spacing to reduces the transmission of
diseases.
• Rouging – diseased plant are collected and destroyed.
Chemical methods
• Spray mancozeb (0.2%) and metalaxyl 2g/ L

10. Disease Name
Pythium rot
Causal agent
Pythium aphanidermatum

11. Systematic position
Kingdom : Fungi
Phylum : Oomycota
Class : Oomycetes
Order : Peronosporales
Family : Pythiaceae
Genus : Pythium
Species : aphanidermatum

12. Pathogen description
• It produces coenocytic mycelium with
sporangiophore.
• The sporangiophore produces the irregular shaped
sporangia which contains vesicles and zoospores
present inside the vesicles.

13. Survival and spread
• Primary spread : Through soil (oospores)
• Secondary spread : Wind borne zoospores.

14. Symptoms
• Flim flesh corm is transfer into soft melodous mass
• In wetland culture – root system is destroyed except
for small fringes near apex of corm.
• Plant become stunted, with leaf stalked shortened and
leaf blades are crinckled and curled.

15. Symptoms
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16. Management
• Sett treatment using capton 4g/L or metalaxyl1g/L

17. Disease Name
Corm rot
Causal agent
Phytophthora nicotianae var. parasitica

18. Symptoms
• Under stagnant condition – collar and tubers get
infected and rotten through breakage of plant.
• Infected roots bocomes dark in colour.

19. Symptoms
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20. Management
• Avoid water stagnation in the field.
• Spraying of chlorine 25 kg/ac followed by
spray of metalaxyl 0.1% and mancozeb 0.2%

21. Disease Name
Soft rot
Causal agent
• Erwinia carotovora sub sp. caratovora

22. Symptom
• Watery rot on the hard portion of tubers within 7 days
• It produces the foul odour

23. Survival and spread
• Primary spread : Water borne bacterium.
• Secondary spread : Farm tools and machineries

24. Symptoms
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25. Management
• Field sanitation.
• Dusting of bleaching powder.
• Spraying of oxytetracyclin.

26. Disease Name
Mosaic disease
Causal agent
Dasheen mosaic virus

27. Symptoms
• Initially plant do not shows any symptoms after 3-4
months , it produces the initial symptom expressions.
• It show the dispresed and vein mosaic pattern on
leaves.
• Finally leaf gets distorted.

28. Symptoms
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29. Survival and spread
• The virus spread through by Aphids –
Myzus persicae (stylet borne)

30. Management:
• Use of virus free planting materials.
• Field sanitation and quarantine measures.

31. REFERENCES
•D. Alice and C. Jeyalakshmi 2018. Plant
pathology, third edition, A.E Publication,
Coimbatore.
•R.S.Singh, Plant diseases, oxford and IBM
Publishing Co. Pvt. ltd. 9th
edition, New Delhi.