5. Contents
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Sr. No. Title Page No.
1 Introduction 7 – 9
2 Diseases caused by fungi on Potato 10 – 19
3 Control Measures for Fungal Diseases 20 – 21
4 Diseases caused by Bacteria on Potato 22 – 29
5 Control Measures for Bacteria Diseases 30 – 32
6 Diseases caused by Nematodes on Potato 33 – 37
7 Control Measures for Nematodes Diseases 38
6. Contents
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Sr. No. Title Page No.
8 Diseases caused by Viruses on Potato 39 – 42
9 Control Measures for Viruses Diseases 43 – 44
10 References 45
7. Introduction
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• Potato ranks third among food crops after wheat and
rice and fifth in total production in Pakistan.
• It produces high energy and nutritional value per unit
area than wheat, rice and maize.
• More than 18 potato diseases are reported in the
country, of which 13 are of common occurrence.
8. Most commonly occurring potato diseases in Pakistan
are
1. Early Blight
2. Powdery Scab
3. Common Scab
4. Black Scurf
5. Stem Rot
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Introduction
9. 6. Soft Rot
7. Brown Rot
8. Wilts
9. Potato Cyst Nematode
10. Root Knot Nematode
• Diseases with MYCOPLASMA PATHOGENS and soil borne
disease of potato caused serious problems in
major potato growing areas of Punjab.
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Introduction
11. Diseases Fungi (Pathogen)
Black Scurf Rhizoctonia solani
Earlry Blight Alternaria solani
Fusarium dry rot Fusarium sp
Fusarium rot Fusarium spp
Late blight Phytophthora infestans
Powdery scab Spongospora subterranean
Wilt/Verticillium wilt V. albo-atrum & V. dahliae
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Diseases caused by fungi on Potato
12. 1. Black Scurf (Rhizoctonia solani)
• Black Scurf is a fungal disease of potatoes
• It is caused by Rhizoctonia solani.
• It is usually found as irregular, black, scab-like marks
on the skin of the tubers.
• These black masses are the resting phase of the
organism and are made up of compacted mycelia,
called “Sclerotia”.
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14. 2. Late Blight
• Late blight is caused by the fungus Phytophthora
infestans.
• Unlike most pathogenic fungi, the late blight fungus
cannot survive in soil or dead plant debris.
• Usually no symptoms appear before the month of
December.
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15. Symptoms of Late Blight
• Late blight appears on potato leaves as
1. pale green,
2. water-soaked spots, often beginning at leaf tips or
edges.
• The circular or irregular leaf lesions are often
surrounded by a pale, yellowish-green border.
• Infected areas on stems appear brown to black.
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17. 3. Early Blight
• Early blight is caused by the fungus Alternaria
solani, which survives in infected leaf or on stem
tissues or in the soil.
• It can also be carried on tomato seed and in potato
tubers.
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18. • On leaves of both crops, the first symptoms usually
appear on older leaves and consist of small, irregular,
dark brown to black, dead spots ranging in size from
a pinpoint to 1/2 inch in diameter.
• This gives the lesion a characteristic "target spot"or
"bull's eye" appearance.
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Symptoms of Early Blight
20. Control Measures for Fungal Diseases
1. Wet poorly drained areas should be avoided for
potato cultivation.
2. Use disease free seed combined with seed
treatment with benomyl.
3. Seed should be planted on raised beds and in
well-drained soil to encourage fast growth of
the seedlings.
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21. Control Measures for Fungal Diseases
4. Harvest the crop as soon as the tubers are
mature, which can reduce the number of
sclerotia on tubers.
5. Apply boric acid before storage.
6. Destroy and burn the plant debris before sowing.
7. Harvest carefully to avoid bruises and injuries to
potato tubers
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23. Diseases caused by Bacteria on Potato
Diseases Bacteria (Pathogen)
Bacterial wilt Ralstonia (Pseudomonas) solanacearum
Black leg and soft rot Erwinia carotovora spp. carotovora and
carotovora spp. atroseptica
Common scab Streptomyces scabies
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24. 1. Common Scab (Streptomyces spp.)
• Common scab produces tan to dark brown, circular or
irregular lesions which are rough in texture.
• Scab may be
1. Superficial (russet scab)
2. Slightly Raised (erumpent scab)
3. Sunken (pitted scab)
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25. Control of Common Scab
• Common scab is controlled or greatly suppressed at
soil pH levels of 5.2 or lower, though a closely
related but less common species of Streptomyces
known as acid scab can survive down to 4.0.
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27. 2. Bacterial wilt(Ralstonia (Pseudomonas)
solanacearum)
• On potato, the disease is also known as “Brown
Rot”, southern wilt, sore eye or jammy eye.
• Bacterial wilt of potato is generally favoured by
temperatures between 25°C and 37°C.
• It usually does not cause problems in areas where
mean soil temperature is below 15°C.
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28. Symptoms of Bacterial wilt
• Typical symptoms are wilting, yellowing and some
stunting of the plants, which finally die right back.
• Symptoms in the tuber are very specific: brownish-
grey areas are seen on the outside, especially near the
point of attachment of the stolon.
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31. 1.Preventative Measures
1. Use of healthy seed tubers.
2. Cultivation in un-infested fields.
3. Destruction of diseased plant debris.
4. Cultural practices to stop spread.
5. Long rotation.
6. Destruction of host plants etc.
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34. Diseases caused by Nematodes on Potato
Diseases
Potato cyst nematode
Root knot nematode (Meloidogyne spp.)
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35. 1. Potato cyst nematode (PCN)
• Potato cyst nematode (PCN) is a serious pest of
potatoes world-wide and is subject to stringent
quarantine and/or regulatory procedures wherever it
occurs.
• PCN can be a devastating pest of potatoes in
temperate regions if not controlled.
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36. Symptoms of Potato cyst nematode (PCN)
• Infested plants are stunted and may wilt, leaves may
yellow or display a dull colour.
• Affected plants have a reduced root system which is
abnormally branched and brownish in colour.
• At flowering or later, minute-white, yellow or brown
spheres or cysts, about the size of a pin head (0.5
mm), can be seen on the outside of roots.
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38. Control Measures for Nematodes
1. Nematodes cyst on root can be observed at
flowering stage.
2. Soil analysis for extraction of cyst also provides an
excellent mean of diagnosis.
3. Use of resistant and tolerant varieties.
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40. Diseases caused by Viruses on Potato
Diseases
Potato leaf roll virus
Potato mop top virus
Potato virus A
Potato virus M
Potato virus S
Potato virus X
Potato virus Y
Phytoplasma
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41. 1. Potato Virus Y
• Potato Virus Y (PVY) can cause necrotic ring spots on
tubers, depending on which strain of the virus is present.
• Affected tubers have roughened rings of darker brown or
reddened skin.
• Necrosis beneath the rings may extend into the tuber
flesh.
• Necrotic symptoms in tubers often increase after storage.
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43. Control Measures for Viral Diseases
1. Use virus free, certified seed potato.
2. Control the aphid vector.
3. Use resistant varieties.
4. Roguing.
5. Heat treatment of tubers.
6. Modification of cropping procedure.
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44. Control Measures for Viral Diseases
7. Chemical control of vector (Insects, nematodes and
fungi).
8. Non-chemical control of vectors (barriers and
reflective mulches, oil sprays, biological control by
predators).
9. Plant resistant to Assess the health of tuber stocks by
serological tests through ELISA, after harvest.
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