early and late leaf spot of groundnut

SYMPTOMS,PATHOGEN, MANAGEMENT

1. COLLEGE OF AGRICULTURAL TECHNOLOGY Affiliated to Tamil Nadu Agricultural University, Coimbatore Kullapuram , Via Vaigai dam, Theni-625 562 EARLY AND LATE LEAF SPOT OF GROUNDNUT STUDENT COURSE TEACHER PREETHI. V Dr. S. PARTHASARATHY ID. No. 2016021034 Asst. Prof., (Plant Pathology )

2. SIGNIFICANCE Groundnut ( Arachis hypogaea ) is one of the important oilseeds and food crops of the world as it provides an inexpensive source of high quality dietary protein and edible oil. Early and late leaf spots, commonly called as tikka  disease in groundnut - economically important foliar fungal diseases.  

3. Infection causes early death of the leaves and dramatic yield loss. This is estimated to range from 10% to 80% and varies according to the environment and availability of control methods. © africasoilhealth.org EARLY LEAF SPOT

4. GLOBAL DISTRIBUTION Leaf spot causes significant yield loss, and can be found wherever Groundnut is grown. This includes areas such as USA, Australia, Fiji, Solomon Islands and Tonga. In India states such as Gujarat,   Andhra Pradesh, Karnataka, Tamil Nadu and Maharashtra. It is estimated that late leaf spot reduces yields by 50% or more in Pacific island countries.

5. SYMPTOMS EARLY LEAF SPOT LATE LEAF SPOT Infection starts about a month after sowing. Infection starts around 5 – 7 week after sowing. Not perfectly circular reddish brown large spot surrounded by yellow halo. Mostly circular dark brown small spots without yellow halo. On lower surface lesion light brown colour . Lower surface lesion carbon black colour . Rapid development Slow development © slideshare.net

6. EARLY LEAF SPOT LATE LEAF SPOT © eplantdisease .net

7. EARLY LEAF SPOT: Cercospora arachidicola (Hori) Sexual stage ( Mycosphaerella arachidis ) Scientific classification Kingdom : Fungi Phylum : Ascomycota Class : Dothideomycetes Subclass : Dothideomycetidae Order : Capnodiales Family : Mycosphaerellaceae Genus : Cercospora Species : C.  arachidicola © eplantdisease .net Fungi- Cercospora arachidicola

8. LATE LEAF SPOT: Passalora personata   ( Berk . & M.A. Curtis) Sexual stage ( Mycosphaerella berkeleyi ) Scientific classification Kingdom : Fungi Phylum : Ascomycota Class : Dothideomycetes Subclass : Dothideomycetidae Order : Capnodiales Family : Mycosphaerellaceae Genus : Passalora Species : P. personata

9. PATHOGEN CHARACTER Cercospora arachidicola The pathogen is intercellular, the mycelium consists of both external and internal hyphae and do not produce  haustoria  and become intracellular when host cells die. The fungus produces abundant  sporulation  on the upper surface of the leaves.

10. Asexual reproduction takes place by means of long, usually hyaline, multiseptate conidia. Conidiophores are olivaceous brown or yellowish brown in colour , unbranched and arise in clusters. Conidia are pale yellow, obclavate .

11. ©icrisat.org LIFE CYCLE OF Cercospora arachidicola

12. © eplantdisease.net CONIDIA

13. Passalora personata The fungus produces internal and intercellular mycelium with the production of haustoria . The conidiophores are long, arise in clusters and olive brown in colour . The conidia are cylindrical or obclavate .  

14. ©icrisat.org LIFE CYCLE OF Passalora personata

15. EPIDEMIOLOGY FAVOURABLE CONDITIONS Prolonged high relative humidity for 3 days. Low temperature (20°C) with dew on leaf surface. Heavy doses of nitrogen and phosphorus fertilizers. Deficiency of magnesium in soil.

16. MODE OF SURVIVAL The pathogen survives for a long period in the infected plant debris through conidia, dormant mycelium in soil.

17. PRIMARY AND SECONDARY SPREAD The primary infection is by ascospores or conidia from infected plant debris or infected seeds. The secondary spread is by wind blown conidia. Rain splash also helps in the spread of conidia.

18. MANAGEMENT Remove and destroy the infected plant debris . Keep weeds under control . Grow moderately resistant varieties like ALR 1 . Varietal screening was carried out with different 16 varieties, among them variety GJG-32 and TG-37A were found resistant and highly susceptible, respectively.  

19. Use of resistant varieties is an ideal, simple and cheapest method for the control of plant disease. CHEMICAL CONTROL Treat the seeds with Thiram at 2g/kg . Spray Carbendazim ( Bavistin ) 500g or Mancozeb ( Indofil M -45) 2 kg/ha.

20. REFERENCES Gupta, V.K., Paul, Y.S., and Sharma Sathish , K. 2012. Fungi and Plant Diseases. Kalyani publishers, New Delhi. Rangaswami , G., and Mahadevan , A. 1999. Disease of Crop Plants in India. PHI learning private limited. http://cec.nic.in/wpresources/module/BOTANY/PaperI/33/content/downloads/file2.pdf http://oar.icrisat.org/821/1/RA_00080.pdf