Potato diseases A lecture on ToT training of FFS By Mr Allah Dad Khan Provincial Coordinator IPM KPK MINFAL Islamabad

2. Potato Diseases
A
Lecture To ToT trainees ( FFS)
By
Mr. Allah Dad Khan
Provincial Coordinator IPM KPK
MINFAL Pakistan

5. Late Blight Symptoms
On potato tubers
Symptoms
• : Infected potatoes have shallow,
brownish or purplish lesions on
the surface of the tuber. If you cut
across the surface of these
infected areas, you’ll see a
reddish-brown, dry, granular rot
that extends up to half an inch
into the flesh. Late blight lesions
can serve as pathways for other
tuber diseases including bacterial
soft rot to enter, so late blight
symptoms can sometimes be
obscured by symptoms of other
diseases.

6. Late Blight Symptoms
On potato plants
Symptoms
• On potato plants: Late blight lesions can occur on
both leaves and stems. The first appearance of
lesions commonly occurs after periods of wet
weather. Black lesions appear within 3-7 days of
infection of leaves. Under humid conditions,
delicate, whitish growth (pathogen spores) are
produced at the edge of the lesion, particularly on
the underside of the leaf. Lesions turn brown when
they dry up. Active lesions are often surrounded by
a halo of gray-green tissue. Once lesions dry up, the
white spore masses will not be visible. To help
identify late blight if outdoor conditions are not
humid enough for spores to be produced, you can
place suspect leaves or stems in a closed container
with a damp paper towel. Check the leaves after
about 12 hours to see if the delicate, white
pathogen sporulation is visible on the tissue at the
edge of the lesion. On stems, late blight causes
brown, greasy looking lesions that frequently
appear first at the junction between the stem and
leaf, or at the cluster of leaves at the top of the
stem.
Late blight lesions on potato
stems.

7. Late Blight
Late blight lesions on tomato
leaflet.
Late Blight on tomato fruit.

8. Early Blight
Symptoms
• Dark lesions with yellow
border which may form
concentric rings of raised and
sunken tissue on the leaves
and stems; lesions initially
circular but become angular;
leaves become necrotic but
remain attached to plant;
dark, dry lesions on tubers
with leathery or corky texture
and watery yellow0green
margins
• Cause
• Fungus
Symptoms of early blight on
potato foliage

9. Early Blight
Close-up of leaf lesion caused by
early blight
Destruction of potato plants by
early blight

10. Verticillium wilt Verticillium dahliae
Verticillium albo-atrum
Symptoms
• Early death of plants;
leaflets dying on only one
side of the petiole or
branching stem; cut through
the stem reveals a
discoloration of the tissue;
discoloration of tubers at
stem-end
• Cause
• Fungi
Yellowing potato foliage caused
by Verticillium infection

11. Black scurf & Rhizoctonia canker
Rhizoctonia solani
Symptoms
• Flat, irregularly shaped black
or dark brown fungal fruiting
bodies on tuber surface;
tubers may be mishapen; red-
brown to black sunken lesions
on sprouts; lesions may girdle
the main stem causing leaves
to curl and turn yellow
• Cause
• Fungus
Death of potato plant due to
infection with Rhizoctonia

12. Black scurf & Rhizoctonia canker
Rhizoctonia solani
Potato tuber covered with fungal
fruiting bodies
Potato tuber covered with fungal
fruiting bodies

13. Leak
Pythium spp.
• Light tan, water soaked area around wound on
tuber; internal rotting of tuber which results in
internal tissue becomes spongy and possibly
developing cavities; dark, watery fluid exudes
from the tuber when squeezed
• Cause
• Fungi
• Symptoms

14. Pink rot
Phytophthora erythroseptica
• Stunted plant growth; wilting leaves; dying
leaves; marked tuber decay; dark brown eyes
on tuber; cut tuber turns pink after 20-30 min
air exposure, then turns brown and finally
black
• Cause
• Oomycete
• Symptoms

15. Black dot
Colletotrichum coccodes
• Small black dots (fungal fruiting bodies) on
tubers, stolons and stems; roots may rot
below ground; leaves may turn yellow and
wilt; infection may cause defoliation
• Cause
• Fungus
• Symptoms

16. Powdery scab
Spongospora subterranea
Symptoms
• White to brown galls on the
roots and stolon; raised
pustules on tuber
surrounded by potato skin;
shallow depressions on
tuber filled with brown
spores
• Cause
• Fungus

17. Common scab
Streptomyces spp.
Symptoms
• Raised brown lesions on
tubers with corky texture;
deep, pitted brown or black
lesions on tuber with straw-
colored translucent tissue
underneath
• Cause
• Bacterium
Tubers showing symptoms of
common scab

18. Blackleg (Soft rot) Erwinia carotovora
Symptoms
• Small, water-soaked lesions on
base of stems originating from
seed piece; lesions may enlarge
to form a large extended lesion
stretching from base of stem to
canopy; tissue becomes soft and
water-soaked and can be lighty
brown to inky black in color;
wilted, curled leaves which have a
soft and slimy texture when wet
• Cause
• Bacterium
Soft rot symptoms on potato
tubers

19. Bacterial ring rot
Clavibacter michiganensis
symptoms
• Wilting stems and leaves;
dying leaves; lower leaves
wilting first; ring of creamy
yellow to brown rot visible
when tuber is cut crossways
• Cause
• Bacterium
Cross-section of infected potato tuber
showing ring of discolored vascular tissue

20. Potato leaf roll
Potato leafroll virus (PLRV)
Symptoms
• Young leaves rolled and
yellow or pink; lower leaves
have leathery texture and
roll upward; necrotic
netting in vascular tissue of
tuber may be present; plant
exhibits an upright growth
habit and growth may be
stunted
• Cause
• Virus

21. Potato virus A Potato virus A (PVA)
• Mild mosaic pattern or mottling on leaves;
severely infected plants may have alternating
patches of yellow and dark green tissue;
leaves may have a shiny appearance; stems
bending outwards slightly
• Cause
• Virus
• Symptoms

22. Potato virus X Potato virus X (PVX)
• Mild mosaic pattern on leaves; severely
infected plants may be dwarved with smaller
leaves; necrosis of plant tops and tubers may
occur
• Cause
• Virus
• Symptoms

23. Potato virus Y Potato virus Y (PVY)
Symptoms
• Symptoms vary widely from mild
mosaic of leaves to leaf necrosis
and plant death depending on
the variety of potato and the
strain of the virus: leaves may
turn yellow and drop from plant;
symptoms may be present on
only one shoot of the plant;
plants with severe leaf necrosis
may produce tubers with light
brown rings on the skin
• Cause
• Virus