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FUNGAL DISEASES OF POTATO
This ppt includes major fungal disease of potato includes Late blight of potato,Early Blight of potato, Black scurf of potato,Leaf blotch of potato and their symptoms , pathogenic characters, epidemiology, management like cultural and chemical management.
2. FUNGAL DISEASES OF POTATO
➢ Late blight of potato
➢ Early Blight of potato
➢ Black scruf of potato
➢ Leaf blotch of potato
3. LATE BLIGHT -Phytopthora infestans
ECONOMIC IMPORTANCE
➢ Historically and pathologically it was the most important disease.
➢ This was the disease responsible for the famous famine in Europe called
Irish famine during 1845- 46.
➢ In India it was first introduced to Nilgiri hills between 1870 and 80.
➢ A severe epidemic occurred first in Nilgiri in 1961.
➢ The main loss in yield is due to defoliation and haulm destruction. Blight
affected tubers rot in the field and storage
4. SYMPTOMS
➢ It affects leaves, stems and tubers.
➢ Water soaked spots appear on leaves, increase in size, turn purple brown&
finally black colour
➢ White growth develops on under surface of leaves.
➢ This spreads to petioles, rachis& stems. It frequently develops at nodes.
➢ Stem breaks at these points and the plant topples over.
➢ In tubers, purplish brown spots and spread to the entire surface on cutting, the
affected tuber show rusty brown necrosis spreading from surface to the center.
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6.
7. PATHOGEN CHARACTER
➢ Mycelium : hyaline ,endophytic mycelium , coenocytic ,highly branched
inter- and intracellular.
➢ Sporangiophores: hyaline ,branched with characteristic swollen ends
where the lemon-shaped
➢ Sporangia are produced, arise in cluster through stomata.
➢ Sporangia pear shaped ,hyaline ,papillate ,multinucleate
➢ Zoospores biflagellate produced at favourable conditions
8. MODE OF SPREAD AND SURVIVAL:
➢ The infected tubers and the infected soil may serve as a source of
primary infection.
➢ The diseased tubers are mainly responsible for persistence of the disease from
crop to crop.
➢ The air borne infection is caused by the sporangia.
EPIDEMIOLOGY :
➢ RH->90% , Temp.-10-25°C and Night temperature:10°C.
➢ Cloudness before rainfall and Rainfall at least 0.1mm and subsequent days
after rainfall.
9. MANAGEMENT
➢ Seed material should be selected from disease free crop in disease free area.
➢ Field sanitation
➢ Wider spacing.
➢ Reduced nitrogenous fertilizers to avoid overcrowding canopy
➢ Tuber contamination is minimized if injuries are avoided at harvest time and storing of
visibly infected tubers before storage.
➢ The resistant varities recommended for cultivation are Kufri Naveen, Kufri Jeevan,
Kufri Alenkar, Kufri Khasi Garo and Kufri Moti
10. CHEMICAL MANAGEMENT
➢ Dipping the seed tubers in fungicidal solutions like COC or 1% Bordeaux
mixture.
➢ Immediately after cutting, treat seed with a recommended mancozeb-based seed
piece fungicide.
➢ Spraying: Earlier days 1% BM sprayed in early stages at fortnightly interval when
the crop is at 15-20 cm ht.
➢ If weather is more favourable once in 7 days Mancozeb 0.25% is effective.
➢ Other fungicides recommended are difolatan, zineb 0.2% and Duter 0.1 – 0.2%,
Daconil 0.1% , COC (0.25) @ 1.5 – 2.5 kg / ha.
11. EARLY BLIGHT - Alternaria solani
➢ Early blight is a very common disease of potato and is found in most
potato growing areas.
➢ This is one of the common diseases of potato and is worldwide in tits
distributors.
➢ In India it is serious on hills as well as on the plains.
➢ It is more common in rabi crop than in Kharif crop.
➢ It appears early in the season (3-4 weeks after sowing)
12. SYMPTOMS
➢ Initial infection usually occurs on the older, lower leaves then progresses up
the plant.
➢ Brown-black necrotic spot-angular, oval shape characterized by concentric
rings.
➢ Concentric rings of slightly raised and depressed dead/brown leaf tissue give
the lesions a “bull’s eye” appearance and produce a ‘target spot’ effect.
➢ Several spot coalesce & spread all over the leaf.
➢ Shot holes on fruits.
13.
14. PATHOGEN CHARACTER
➢ Mycelium: septate, branched, light brown
which become dark at age, intercellular and
later intracellular
➢ Conidiophores - dark coloured emerge
through stomata.
➢ Conidia - born in chain, club – shaped,
muriform with 5-10 cross septa and 1-5
longitudinal septa with long beak.
15. MODE OF SPREAD AND SURVIVAL
➢ The conidia and the mycelium in the soil or in the debris of the affected plants
can remain viable for more than 17 months.
➢ Primary infection:
○ These conidia or the new conidia found on the overwintered mycelium
➢ Secondary infection :
○ The conidia formed on the spots developed due to primary infection are
disseminated by wind to long distances.
○ The conidia from the affected plant may also be disseminated to the
adjoining plants by rain and insects..
17. MANAGEMENT
➢ Disease free seed tubers should be used for planting.
➢ Removal and destruction of infected plant debris should be done because the
spores lying in the soil are the primary source of infection.
➢ Very early spraying with Zineb or captan 0.2% and repeating it for every 15
– 20 days gives effective control.
➢ The variety Kufri Sindhuri possesses a fair degree of resistance.
18. Black scurf: Rhizoctonia solani
SYMPTOM:
➢ Black speck, black speck scab, russet scab on tubers.
➢ At the time of sprouting dark brown colour appear on the eyes.
➢ Affected Xylem tissue causes to wilting of plants.
➢ Infected tuber contains russeting of the skin.
➢ Hard dry rot with browning on internal tissue.
19.
20.
21. PATHOGENIC CHARACTER
➢ The fungus is characterized by the right angle branching of the hyphae.
➢ The hyphae are clear in young, but turn brown with age
MODE OF SPREAD AND SURVIVAL:
➢ Rhizoctonia diseases are initiated by seed borne or soil borne inoculum.
➢ The sclerotia on the seed tubers is the principal source of infection of the
subsequent crop raised with these tubers.
➢ On return of favourable conditions the mycelium present in the soil may
develop producing new hypae.
22. EPIDEMIOLOGY
➢ Seed tubers are source of spread.
➢ Moderately cool, wet weather and temp 23 °C are the favourable for the
development of disease.
➢ Disease develops more in sandy soil than clay.
➢ Cool temperatures, high soil moisture, fertility and a neutral to acid soil (pH 7
or less) are thought to favor development of Rhizoctonia disease.
23. MANAGEMENT
➢ Disease free seed tubers alone should be planted.
➢ If there is a slight infection of black scurf that can be controlled by treating seed
tubers with mercuric chloride solution for 1.5 hr with acidulated mercuric
chloride solution for 5 min.
➢ Treating the soil with pentachloronil trobenzene at the rate of 70 kg/ ha
lowers the incidence of the disease, but it is too expensive and cumbersome.
➢ Well sporulated tubrs may be planted shallow to control disease.
➢ The disease severity is reduced in the land is left fallow for 2 years.
24. LEAF BLOTCH: Cercospora concors
SYMPTOMS
➢ Circular or irregular pale green or light purple spots first appear on lower
leaves.
➢ The spots may be covered with grayish fungal growth.
➢ The spots enlarge and coalesce to form big blotches on the lamina.
25. PATHOGENIC CHARACTER
➢ Conidiophores and conidia form on the underside of the lesions, giving
the lesions a mildewed appearance similar to late blight
➢ The conidiophores were irregular in width, grayish, and highly branched.
➢ The conidia were numerous, light to dark, straight or slightly bent,
cylindrical or obclavate, with conspicuous scars, and zero to six septa.
26. MODE OF SPREAD:
➢ Infected plant debris act as primary source
➢ Sec. Spread through conidia carried by wind, rain etc.
EPIDEMIOLOGY:
➢ Cool and wet weather favour disease development.
➢ Optimum temp for germination of conidia 20 C
27. REFERENCES
https://agritech.tnau.ac.in/crop_protection/crop_prot_crop%20diseases_veg_potato_4.html
Arora R.K , S. M. Paul Khurana.2004 .Major Fungal and Bacterial Diseases of Potato and their Management.Fruit and
Vegetable Diseases.Volume 1.ISBN : 978-1-4020-1976-0.
http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_LateBlt.htm
https://www2.ipm.ucanr.edu/agriculture/potato/Early-Blight/
https://www.biologydiscussion.com/plants/plant-diseases/early-blight-of-potato-with-diagram-plant-diseases/64337
http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/PublishingImages/PotatoTomato01sm.jpg
http://agropedia.iitk.ac.in/content/black-scurf-potato
Tian SM, Ma P, Liu DQ, Zou MQ. First Report of Cercospora concors Causing Cercospora Leaf Blotch of Potato in Inner
Mongolia, North China. Plant Dis. 2008 Apr;92(4):654. doi: 10.1094/PDIS-92-4-0654C. PMID: 30769662.
