patato disease

1. Potatocrop Diseases, Symptoms, Etiology, Disease cycleand
Their Management.
: Alternaria solani
: Phytopthora infestans
: Rhizoctonia solani
: Potato leaf roll virus
1. Early blight
2. Late blight
3. Black scurf
4. Leaf roll
5. Mosaic
a. Mild mosaic/Interveinal mosaic
b. Severe mosaic
c. Rugose mosaic of potato
: (Potato virus X) PV X
:Potato virus Y (PV Y)
: Potato virus X &Y
Disease Causative agent

2. Nine fungal, one root nematode, one bacterial and four viral diseases were
recorded on potato in Ethiopia.
Early blight (alternaria solani),bacterial wilt (rastonia Solanacearum),late blight
(phytophthora infestans) and viruses were the most widely distributed potato
diseases in all of the areas surveyed during 1993 and 1994 seasons.

3. 1. Symptoms:
This is a common disease of potato occurring on the foliage at any stage of the
growth and causes characteristic leaf spots and blight.
Normally the disease symptoms become apparent during tuber bulking stage
and develop leading to the harvest.
The early blight is first observed on the plants as small, black lesions
mostly on the older foliage.
Spots enlarge, and by the time they are one-fourth inch in diameter or larger,
concentric rings in a bull's eye pattern can be seen in the center of the diseased area.
Tissue surrounding the spots may turn yellow.
If high temperature and humidity occur at this time, much of the foliage is killed.
1. Early blight: Alternaria solani

4. spread
 Etiology:
 The mycelium is septate, branched, light brown colour, inter and intracelluar in the host
tissue.
The conodiophore are short, light brown, septate arise from disease tissue and emerge
through stomata.
The conidia are borne in chain at tip of conidiophores.
Conidia are obclavate, muriform with 5-10transverse septa.
Lesions on the stems are similar to those on leaves, sometimes girdling the plant if they
occur near the soil line.
1. Symptoms……

5. Disease Cycle/perpetuation of Early blight of disease:
 Primary Infection: Mycelium or conidia in infected plant debris
Secondary Infection: C onidia dispersed by wind, water or rain
splashes
Management of early blight disease
 Use of disease free seed
 Practicing crop rotation helps to minimize the disease incidence.
 Removal and burning of diseased crop debris
 Nursery spraying after 2 weeks after sowing with CO C 50WP
 Mancozeb@0.25% or chlorothalonil@0.2% or Zineb@ 0.25% spray at weekly
intervals.
 Spray Mancozeb + urea solution i.e. at the rate of 2 g Mancozeb 75 WP + 10 g
urea per litre of water at 15 days interval when symptoms start.

6. 2. LATE BLIGHT : PHYTOPTHORA INFESTANS
Symptoms:
A. Symptoms on leaf
• The first symptoms of late blight in the field are
small, light to dark green, circular to irregular -
shaped water-soaked spots.
• These lesions usually appear first on the lower
leaves. Lesions often begin to develop near the leaf
tips or edges, where dew is retained the longest.
• During cool, moist weather, these lesions expand
rapidly into large, dark brown or black lesions,
often appearing greasy.
• Leaf lesions also frequently are surrounded by a
yellow chlorotic halo.

7.  The lesions are not limited by leaf veins, and as new
infections occur and existing infections coalesce, entire
leaves can become blighted and killed within just a few
days.
 The lesions also may be present on petioles and stems
of the plant.
 The lesions are not limited by leaf veins, and as new
infections occur and existing infections coalesce, entire
leaves can become blighted and killed within just a few
days.
 The lesions also may be present on petioles and stems
of the plant.
A. Symptoms on leaf
2. LATE BLIGHT : PHYTOPTHORA INFESTANS….

8. Late blight infection of tubers is characterized by:
irregularly shaped, slightly depressed areas that can vary considerably from
brown to purplish of variable size on the skin.
A tan to reddish-brown, dry, granular rot is found under the skin in the
discolored areas and extending into the tuber usually less than ½inch
B. Symptoms on tubers:
2. LATE BLIGHT : PHYTOPTHORA INFESTANS….

9. Etiology of P. infestans :
Mycelium is coenocytic, hyaline, branched and both inter and intracelluar
The conidiophores are aerial and arise from the internal mycelium through stomata
and lenticel on the tubes.
They are slender hyaline, branched and indeterminate.
The sporangia are thin walled, hyaline, oval or pear shaped with a definite papilla
at the apex germinating by zoospore. Oospore are thick walled and yellowish.
Disease cycle:
 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.

10. Disease spread and Development
 Appearance and build-up of late blight depend solely on weather conditions.
 There are specific requirements of temperature and humidity for initiation and
further build up of disease.
1. Temperature
Pathogen growth - 16-20oC
Spore production - 18-22oC
Spore germination - 10-20oC
Infection and disease development 7.2-26.7oC(18+1oC)
2. Humidity
 Spores are formed in moisture saturated
atmosphere.
 Spore germination and infection requires 100 per
cent humidity.
 Spores get killed under low humidity (less than
75% humidity)
3. Light
 Spores are produced during the
night and are sensitive to light.
 Cloudiness favours disease
development.

11. • In Ethiopia the disease caused 100% crop loss on unimproved local cultivar, and
67.1% on a susceptible variety (Bekele and Yaynu 1996).
• Late blight is a major limitation to potato production in high humid elevations;
with estimate average yield losses of about 30–75% on susceptible varieties
(Olanya et al. 2001).
• Research centers have made estimates of losses ranging from 6.5 to 61.7%,
depending on the level of susceptibility of the varieties (GILB and CIP 2004a).
• According to Fekede et al. (2013); Binyam et al. (2014b), reports, in Ethiopia
late blight of potato causes tuber yield losses of 21.71– 45.8% and 29-57%
depending on the resistance level of the cultivars, respectively.
• Late blight can occur at any time during the growing season, it is more likely to
be seen in late summer and early autumn (Bevacqua 2000).
ECONOMIC IMPORTANCE OF LATE BLIGHT OF POTATO

12.  Use of disease free seed.
 Selection of well drained soils.
 Destruction of plant debris.
 High ridging.
 Scouting of the field.
 Stop irrigation when conditions become congenial.
 Haulm cutting at 75% disease severity.
 Harvesting should be done 15-20 days after haulms cutting.
 Treat seed tubers with boric acid (30g per litre of water) before storage.
Integrated Disease Management

13. Host resistance
Host resistance to late blight is of significance in integrated late blight
management due to its long-term economic benefits for farmers.
It also minimizes changes in the population structure of P. infestans, decreasing
the likelihood of fungicide resistance (Hakiza 1999; Mukalazi et al. 2001).
The use of resistant varieties is among the most effective and environmentally
safe means of managing the disease.
The resistant varities recommended for cultivation in Ethiopia are:

14. Chemical Management
 Prophylactic spray with contact fungicides like mancozeb (0.2%) or
chlorothalonil (0.2%) or propineb (0.2%) before the closure of canopy.
 On appearance of the disease, spray the crop with fungicides like
dimethomorph -based or cymoxanil -based or fenamidone - based @0.3%.
 Depending upon disease severity and weather conditions, number of spray may
be increased or decreased.
 Ensure thorough coverage of plants top to bottom with fungicides.
 Special attention should be given to lower leaves which need to be covered with
fungicides.
 Do not wait or allow late blight to appear and establish in the field.
 Always use a sticker @0.1% for proper sticking and uniform spread of
fungicides on leaf surface.

15. Symptoms can be observed on above and below ground plant parts.
Symptoms observed above ground early in the season include necrosis at the
tips of the sprouts and sunken lesions on stolons, roots, and stems.
Later in the season, sclerotia are produced in the tubers creating a sign called
black scurf which is simply, sclerotized mycelium.
 Stems with cankers can become girdled, resulting in stunted plants.
 Leaves of infected plants develop a purplish and chlorotic coloration.
 In severe infections, green tubers develop above the ground.
Affected tubers are deformed and can produce sclerotia on the surface.
3. BLACK SCURF : RHIZOCTONIA SOLANI
 Symptoms

16. Tuber russet
Sunken leisons on stem
Etiology:
Rhizoctonia solani is a basidiomycete fungus that does not produce any asexual spores
(called conidia) and only occasionally will the fungus produce sexual spores
(basidiospores).
In nature, R. solani reproduces asexually and exists primarily as vegetative mycelium and/or
sclerotia
Young mycelium of R Solani is silvery and become yellow to brown at maturity 8- 12 µm
in dia.
Having frequent septation and branched. Sclerotia are dark brown to black.
They are roughly spherical or somewhat flattened or irregular, shape of micro scleortia
is oval to irregular

17. Disease Cycle
P.I: Oospores (Pythium) or Sclerotia (Rhizoctonia) in soil
S.I: Seedlings raised in infected soil carry the disease to field
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 pentachloroni trobenzene at the rate of 70 kg/ ha lowers the
incidence of the disease, but it is too expensive and cumbersome.
Well sprouted tubers may be planted shallow to control disease.
The disease severity is reduced in the land is left fallow for 2 years.

18. 4. Leaf roll : Potato leaf roll virus
Symptoms:
 The symptoms appear early and young leaves show an upward roll.
Leaves become dry, leathery and thick.
They turn brittle and give their distinctive rattle when shaken.
 Plants may also be severely stunted, erect and light green.
Tubers are reduced in size and number. With some varieties, a net necrosis
develops inside the tuber.

19. Transmission
 Infected tubers (Sap inoculation)
 Spread by aphids, Myzus persicae and Aphis gossypii
Management:
 Disease free seed tubers for planting.
 Use of disease free certified seed.
 Rouging of diseased plants and burying them deep in soil.
 Aphid control.(Phorate 10G ,10Kg/ha or monochrotophos).

20. : (Potato virus X) PV X
5.Mosaic :
a. Mild mosaic/Interveinal mosaic
 Symptoms:
 Often referred as latent potato mosaic
 Light yellow mottling with slight crinkling on potato plants
 Interveinal necrosis of top foliage
 Stunting of diseases plants
 Leaves may appear slightly rugose where strains of PV Y combines

21. Also called potato leaf drop streak
B) SEVERE MOSAIC – POTATO VIRUS Y (PV Y)
 Symptoms
Chlorotic streaks on leaves which become
necrotic
Necrosis of leaf veins and leaf drop streak
Interveinal necrosis and stem/petiole
necrosis
Plant remain stunted in growth
Rugosity and twisting of the leaves occurs in
combination with PV X and PV A

22. Symptoms
 Black streaks appear in leaf veins and on stems.
Early-season infection shows shriveled leaves that hang from
the stem by a thread of dead tissue.
Later in season, the plants become bare with a few leaves on
top. Late- season infection does not show any symptoms.
Plants from infected seed tubers have mottled and wrinkled
leaves that are distorted ("rough") and reduced.
Stems are brittle and dwarfing is common. Harvested tuber size
is greatly reduced.
The primary pathogen is Potato Virus Y (PVY) which may act
alone or in conjunction with PVX.
There are many strains of PVY with differing characteristics
and behaviour.
PVY is spread by both seed and aphids.
C. Rogose and Common Mosaic : Potato virus X &Y

23. Transmission
a.)Mild mosaic/Interveinal mosaic
Spreads mechanically through rubbing of leaves, contact of infected plants (Sap
inoculation), seed, cutting knives, farm implements.
Root clubbing of healthy and diseased plants in field
b) Severe mosaic – Potato virus Y (PV Y)
Infected tubers (Sap inoculation)
Spread by aphids, Myzus persicaeandAphis gossypii
 Management:
Disease free seed tubers for planting.
Resistant varieties (like chippewa & Irish cobs).
Use of disease free certified seed.
Rouging of diseased plants and burying them deep in soil.
Insect control in case of Mild and Rugose mosaic.(Phorate 10G ,10Kg/ha)
Avoid working of labour and animals from diseased to health crop in case of latent
mosaic virus.
Early harvesting of the crop.

24. 6. Bacterial wilt (Ralstonia/Pseudomonas solanacearum)
 Bacterial wilt also known as Brown rot, and southern bacterial wilt, is a
bacterial disease of the potato that is extremely destructive in tropical and
subtropical regions.
 The causal organism for this disease is a gram-negative, short-rod bacterium
with one polar flagellum.
 In Ethiopia, Bacterial wilt of potato was first recorded in 1956 on potato and
egg plant in the Keffa region.
 Apart from solanaceous crops like chilli, potato, tomato, and eggplant the
pathogen has been known to attack a large number of other plants including
castor, groundnut, banana and ginger.
 It is very often associated with the root knot nematodes which affect potatoes
and tomatoes.

25. Bacterial
Wilt of
Potato
Inoculum Source
Diseased potato Infested soil
Tubers & plants
Seed tubers
Irrigation water
Soil in tools, hooves, shoes
Nematodes & insects in soil
Host crops & weeds
Harvest left over
Volunteers
Soil
Mode of spread and survival

26. Symptoms
 Bacterial wilt of potatoes appears as sudden wilting of one or more stems of the
potato plant.
 This symptom can be mistaken for water stress.
 Plants may also look stunted and begin to yellow.
 Brown discolouration is visible in the vascular tissues of the stem and tubers.
 When stems or tubers are cut and slight pressure applied, creamy bacterial slime
comes from the infected vascular elements.
 Bacterial slime oozes from the eyes of tubers and soil sticks to the tubers where
the slime has emerged.
 Secondary infection can cause decay of the whole tuber.
 External symptoms and internal browning are not always visible in infected
plants, and potato tubers can be infected without any visible symptoms.

27. Symptom of Bacterial wilt (Ralstonia solanacearum)…
 when cut and oozing of milky fluid from the vascular ring of cross-sectioned
tubers were the most commonly encountered disease symptoms.
Symptoms of potato brown rot with bacteria oozing from cut vascular tissues (a) and eyes (b)
(and wilted plant in the field (c) .

28. Disease cycle & Epidemiology
 Bacterial wilt pathogen can survive in soil (without a host for several seasons),
water, seed tubers, potato plant remnants.
 The wilt bacterium is able to survive for periods up to 2-3 years in bare fallow
soils, and for longer periods in soils cropped to non-solanaceous crops.
 The disease can spread from field to field or from plant to plant within field via
infected seed, air, water, soil, farming tools, livestock and people.
 Spread of bacteria by aerial means and subsequent plant contamination through
foliage is not known to occur.
 However, bacteria move from roots of infected plants to roots of nearby healthy
plants, often via irrigation practices.
 Soilborne organisms, such as the root-knot nematode, can cause injury to plant
roots and favor penetration of the bacterium.
 High temperature (85-95°F), soil moisture and low pH favours disease
development.
 The disease spread rapidly in the warmer temperatures in storage areas. Infected
seed can also be a source of the disease in the field.

29. Management methods of R. solanacearum
• Use of healthy seed
• Do not cut seed tubers. Cutting spreads pathogen even to healthy tubers.
• Apply stable bleaching powder @12kg/ha mixed with fertilizer in furrows
while planting. It reduces wilt incidence by 80%.
• 2-3 years crop rotation with n o n h o s t c r o p s s u c h a s maize, cereals,
millet, garlic,onion, cabbage, etc .
• Full earthing up. Deep ploughing twice at 20-30 days interval after harvest
during summer in plains and in winter in hills.
• Biological control: The use of rhizosphere resident microbial antagonist
specifically the fluorescent pseudomonas is noted as a promising control
method.

30. Favourable condition
 Disease development is favoured by warm temperatures (25° – 35°C) and is limited
by temperatures below 10°C.
 RH above 50 % and PH 6.2-6.6 is also favours for the development of disease.
 Acid soil is not favourable.
 Soil moisture is important as the bacterium cannot tolerate dry soil conditions.

31. DISEASES OF TOMATO AND THEIR MANAGEMENT
Common Disease of tomato
 Tomato Diseases can be:
 Fungal disease
 Bacterial disease
 Viral disease
 Nematode disease
Bacterial disease includes
• Bacterial canker
• Bacterial spot
• Bacterial wilt
• Bacterial speck
Fungal disease includes
• Early bligh
• Fusarium wilt
• Anthroconose
• Late blight

32. Fungal disease (Early blight)
 Caused by Alternaria solani
SYMPTOMS
 Early blight shows up as small, irregular, brown, dead spots on lower, older leaves.
 The spots then grow to ½-inch in "bulls-eye" patterns.
 The whole leaf then may go yellow.
 As fruit begins to occur, when suffering from blight, the older fruits may show dark
leathery sunken spots.
 It can be diagnosed in stems as well (Kemmitt, G. 2013).

33.  Leaf spots and blight on the foliage.
 The disease first becomes visible as small,
isolated, scattered pale brown spots on the leaf.
 Spots are irregular, brown to dark brown in
colour, and with concentric rings inside the spot.
 Often several spots coalesce to form large
patches resulting in the leaf blight.
 Lowest leaves are attacked first and the
disease progresses upwards.
SYMPTOMS of tomatoearly blight

35. DISEASE CYCLEAND EPIDEMIOLOGY
Infection by the fungus is most rapid under warm (28-30°C) wet conditions.
Survives between crops in plant debris and on seed.
It can also survive on volunteer tomato plants (warm climates) and on other
cultivated and wild solanaceous plants (potato, eggplant, horse nettle and black
nightshade).
Early blight symptoms (leaf spot and defoliation) are most pronounced in the lower
canopy.
Disease severity and prevalence are highest when plants are loaded with fruit

36. DISEASE CYCLE

37. FAVOURABLE CONDITION :
 Disease develops at moderate to warm 15 to 27 degree celsius;
 Rainy weather or heavy dew, 90% humidity ,
 June-July sowing - weak and old plants prone to infection high soil
moisture.
Mode of spread:
 Seed borne and air borne conidia

38. Management
CULTURAL CONTROLS
 Use pathogen-free seed and transplants.
 Maintain plant vigor through adequate
irrigation and fertilization to increase disease
resistance.
 Use long rotations away from tomato and other
solanaceous crops, avoid planting tomato near
related
 crops that are more mature and eliminate weed
hosts.
 Avoid plant injury which allows entry of the
pathogen and spread of the fungus through
adequate insect management.
 CHEMICALCONTROL
 Contact fungicides such as
 chlorothalonil and mancozeb provide
moderate levels of control when
applied preventively.
 Newer chemistries including;
 strobilurin fungicides
(azoxystrobin, pyraclostrobin,
etc.) have provided excellent
control in university trials.
 Mancozeb (0.175%), chlorothalonil or
copper fungicides (0.125 %).
 Hot water Treatment of seeds for 25
mints at 50°C.
R
E
S
I
S
T
ANCE MANAGEMENT
No resistant varieties avaliable

39. LA
TEBLIGHTOFTOMA
TO(Phytophthora infestance)
• Late blight is a potentially devastating disease of tomato and potato,
infecting leaves, stems, and fruits of tomato plants.
• The fungus are not a true fungus, but rather is regarded as a fungus like
organism.
• Worldwide distribution, but most severe epidemics occur in areas with frequent
cool, moist weather.
• The host range is mainly limited to solanaceous crops, including tomato,
nightshade (Solanum nigrum) and potato.
• Sweet potato (Ipomea batatas) is not a host for late blight.
• The disease spreads quickly in fields and can result in total crop failure if
untreated.
• phytophthora in Latin means "plant destroyer." Infected plant tissue dies.

40. Signs and symptoms of Tomato late blight
On Leaves :
⚫ Leaves have large, dark brown blotches with a green gray edge; not confined by major
leaf veins
⚫ Infections progress through leaflets and petioles, resulting in large sections of dry
brown foliage.

41. On Stem :
⚫ Stem infections are firm and dark brown with a rounded edge.

42. On tomato fruit:
 Such infected fruits are not fit for human
consumption.
They should be removed from affected gardens
and destroyed.
The fruit damage that appears in this photograph
can occur in a few days or less under the right
weather conditions.
 Infected tomato fruits turn greasy, olivaceous-brown, decay, and can shrivel up and fall off
the plant and never ripen.

43.  Select a tomato variety that reaches maturity quickly.
 Stake up tomato plants, especially indeterminate types. Keep
 tomato stems and branches away from the ground.
 Plant blight-resistant tomato varieties when they become available.
 Intercrop tomato with non-susceptible host plants, preferably non-solanaceous
plants.
 Practice good crop sanitation; inspect the plants regularly and remove
diseased material from the plot .
 Destroy volunteer tomato plants.
 Avoid moving through the tomato garden or field when plant foliage is wet.
 Control solanaceous weeds around the tomato garden. Prophylactic sprays with
copper fungicides or dithiocarbomates 0.25% .
 Metalxyl / amiston 0.2%.
MANAGEMENTAND CONTROL

45. FAVOURABLE CONDITIONS:
 High relative humidity >90 %
 Low temperature 10 – 25 degree celsius
 Cloudy weather and rainfall with splashing rains.
DISEASE CYCLE :
 PSI : Oospores in the infected debris and soil.
 SSI : Sporangia or zoospores dispersed by wind or rainwater
Mode of spread:
 Soil borne-spread through sporangia or zoospores
dispersed by wind or rainwater.

46. Difference between tomato early and late blight

47. Tomato Fusarium wilt
Symptom
 Clearing of the veinlets and chlorosis of the leaf.
 Soon the petiole and leaves droop and wilt.
 The younger leaves may die
 Dark brown or black discoloration of the vascular tissues.
 Fungus survives saprophytically in soil.

48.  Use resistant Variety
 pH 6.5 to 7.0
 Keeping tomato plants weed-free.
 Avoid activity in wet plantings
Prevention & Treatment
 Use nitrate-based nitrogen fertilizer, such as calcium nitrate, rather
than an ammonia-based nitrogen fertilizer.
 Seed treatment with 4 g Trichoderma viride formulation or 2.5 g
Carbendazim per kg seed is effective.