POTATO diseases 2020

1. POTATO LATE BLIGHT
 Symptoms: Black/brown lesions on leaves and stems,
small at first and appear water-soaked or chlorotic borders,
but soon expand rapidly and become necrotic.
 In humid conditions, Phytophthora infestans produces
sporangia and sporangiophores on surface of infected
tissue.
 This sporulation results in a visible white growth at the
leading edge of lesions on abaxial (lower) surfaces of
leaves.
 Lesions merge, entire plant destroyed in only a few days
after the first lesions.
Management of late blight of potato
 Planting pathogen-free tubers: Only certified seed tubers
 Fungicide treatments: Protect freshly cut seed tuber
 Irrigation: Minimum to prevent foliar infection.
Timed to allow plants for drying. Never excess.
 Tubers: Infected in field, discard rotten tubers .
(1) Copper oxychliorde (Blitox), (2) Mancozeb (Dithane M 45),
(3) Fosetyl Al (Alitte), (4) Propineb (Antracol),
(5) Metalaxyl (Ridomyl) (6) Mefenoxam (SubDueMaxx),
(7) Propamocarb (Previcur N 72) (8) Mandipropamid (Revus)
(9) Dimethomorph (Acrobat), (10) Cymoxanil (Curzate),
(11) Fludioxonil (Maxim PSP) (12) Cyazafamid (Ranman)
(13) Fenamidone + mancozeb (Sectin) * Spray @ 30 days interval #Dose: @ 2 - 3 ml/L
Fungicides
Wild fire in moist cool
environment at 10 - 15
- 20° C, RH 75 - 90 %.

3. BACTERIAL WILT IN BRINJAL AND ITS MANAGEMENT
The brinjal cultivation is mainly affected by Bacterial Wilt (BW) and is a major
production constraint. The local cultivars are highly susceptible and incidence
ranges from 30-100%.
It is caused by Ralstonia solanacearum, a soil bacterium, formerly Pseudomonas
solanacearum. It has five different races, each infecting different plant species. Its
strains are grouped into five biovars. Mostly race 1 and biovars 3 is involved.
It has an unusually wide host range of 200 plant species belonging to more than 50
families. Majority of the hosts are dicots with the major exception being bananas
which makes its management difficult.
BW is a soil borne disease and able to survive in the soil for long periods from one to
ten years without a host plant. Many weeds serve as the symptom-less carrier.
Favorable conditions: The disease occurs on all the types of soil, including sandy and clay
soils. BW incidence was mostly prevalent in the acidic soils (soil pH < 7.0). High temperature
and moisture are favorable. Root knot nematode predisposes the plant.
Symptoms: Initially leaf drooping followed by wilting of entire plant within a few
days. Vascular wilt with yellowing of leaves. Vascular discoloration (brown in the
wilted plant. Bacterial ooze from infected plant.
Diagnosis: A stream of milky white bacterial ooze can be noticed when the cut ends of
the stem/root is kept undisturbed for few minutes in a clear container with water.
In the laboratory, if the bacterial ooze is streaked in TZC medium, circular to oval
shape, fluidal colonies with pink centre will appear after 48 hours which is unique
to R. solanacearum.
Molecular biology techniques like PCR used for soil and plant sap. Bacteria can be
seen by amplifying the specific region from its genome.

4. 1. Plant in a disease free field. Fields that have no previous history of BW with susceptible hosts. Regular rotation with
other non-host plants. However, rotation with paddy for only one season doesn't make the field disease free.
2. BW resistant varieties viz. Surya, Swetha and Haritha
3. Fumigate/ solarize nursery soil for 15 days prior to sowing.
4. Prevent the spread of the pathogen. Infected plants should be removed and destroyed and also the infected portion of
the field should be isolated if possible by preventing the water flow into and from the field.
5. Frequency of irrigation and quantity of water should be reduced. Flood irrigation in the infected field increases the
disease incidence by two fold. Movement of people/machinery should also be limited.
6. Reduce the pathogen load in infected field Once introduced in to the field, R. solanacearum are very difficult to
eradicate but the pathogen population/load can be reduced by following methods in orderto reduce the disease
incidence:
7. Fumigation with chemicals like methyl bromide. However, it is highly toxic and not practical for small scale farmers.
8. Crop rotation with paddy and other non-host crops for 3-4 seasons.
9. Flooding the field for 1-3 weeks before planting will reduce BW.
10. Growing marigold (Tagetes spp.) in rotation or as intercrop will suppress the pathogen in addition to its anti-nematode
effect. Growing Brassica spp. and incorporating the plants into soil at flowering stage will reduce BW incidence.
11. Application of organic manures like FYM/ poultry manure in every year will increase the beneficial soil microflora
and reduce the BW incidence.
12. Biological control: Treat the seeds with talc based formulation of antagonistic Pseudomonas f1uorescens
(1Og/1OO g of seeds) and soil application of antagonistic P. f1uorescens (50g mixed with one kg of
soil and incorporated in the nursery bed).
13. Main field treatment: Dip the seedlings in the antagonistic P. f1uorescens/ B. subtilis (@ 259 talc
formulation per litre of water) solution for 20-30 minutes just before transplanting. The left-over
solution should be drenched around the root zones (50ml/plant).
14. Treatment with biological control reduced BW by more than 65 per cent with increase of yield (28 to
54%).
15. Integration of biological control agents with soil solarization and organic amendments.
Brinjal Bacterial Wilt Management

5. Brinjal Bacterial Wilt Management
• Prevention:
• Summer Ploughing Crop rotation with cereals or cruciferous
vegetables
• Apply neem cake @ 100 kg /acre to reduce bacterial pathogen
• Solarisation of nursery beds
• Field sanitation by ensuring weed free field. Keep land fallow for a
season to destroy harmful pathogens
• Avoid water logging and provide drainage facility.
• Use resistant variety namely Pant Samra.
• Monitoring:
• Observe for dropping of lower leaves at mid sunny days
• Observe for vascular browning Discharge of milky streaks of bacteria
from the ends of cut stems when placed in a glass of water.
• Direct Control :
• Rouging of diseased plants and burn and Periodically remove infected
plants
• Rouging of diseased plants and then drench in and around diseased
area with copper hydroxide 77%WP @ 3 gms per litre.
• Apply basally talc based 2.5 kg Pseudomonas fluorescens /ha pre-
colonized in farm yard manure
• www.plantwise.org

6. Indian Agriculture
• India feeds 17 % of world’s population
• With its 2.3 % of world’s land area
• And 4.2% water resources
• Having only 140 million hectares net
cultivated area.

7. Bacterial wilt
Survival and spread:
• Bacterial wilt pathogen can survive in soil
(without a host for several seasons), water,
seed tubers, potato plant remnants.
• 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.
• Favourable conditions:
• High temperature, soil moisture, low pH.
• The disease spread rapidly in the warmer
temperatures in storage areas.
• Infected seed can also be a source of the
disease in the field.
Symptoms:
Besides, potato, the pathogen also
damages plants such as chili, tomato,
tobacco and egg plant.
Infected plant begins to wilt, starting
from the tips of the leaves or where the
stems branch out, and then spreading to all
parts of the plant.
Leaves become yellow at their bases,
then the whole plant wilts and dies. When
stems are cut a brown colored ring will be
visible.
When a tuber is cut in half, black or
brown rings will, however, be visible. If
left for a while or squeezed, these rings will
exude a thick white fluid.
A further symptom is fluid coming out of
tuber eyes. This can be signified by soil
sticking to tuber eyes when crops are
harvested. Serious infection causes tubers
to rot.

8. Septoria leaf spot
• Disease symptoms:
• Less vigorous plants are usually affected
• Small, round to irregular spots with a grey center and dark
margin on leaves
• Spots usually start on lower leaves and gradually advance
upwards
• At later stage spots coalesce and leaves are blighted
• Complete defoliation of affected leaves may take place.
• Stems and flowers are sometimes attacked
• Survival and spread:
• Primary: Mycelium or conidia found in pycnidia in infected
plant debris or on solanaceous weeds
• Secondary: Conidia spread through rain splash or wind and
also by slimy conidia sticking on to hands and clothing of
potato pickers.
• Favourable conditions:Poor vigour of plants due to nutrient
deficiency in late season
• High humidity or persistent dew at 25 ºC
• Moist weather with intermittent showers.
• Favourable
conditions:Poor
vigour of plants due to
nutrient deficiency in
late season
• High humidity or
persistent dew at 25 ºC
• Moist weather with
intermittent showers.

9. Late blight
Disease symptoms:
This disease damages leaves, stems and
tubers. Affected leaves appear blistered as if
scalded by hot water and eventually rot and
dry out.
When drying out, leaves turn brown or black
in color. When infections are still active, spots
appear on the underside of leaves blanketed in
what looks like flour.
Affected stems begin to blacken from their
tips, and eventually dry out.
Severe infections cause all foliage to rot, dry
out and fall to the ground, stems to dry out
and plants to die.
Affected tubers display dry brown-colored
spots on their skins and flesh. This disease acts
very quickly. If it is not controlled, infected
plants will die within two or three days
Survival and spread:
he pathogen survives in plant
debris in the soil.
It spreads through soil and
infected seed tubers.
Favourable condition:
High humidity
Low temperature and leaf
wetness

10. Early blight
• Disease 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.
• Lesions on the stems are similar to those on leaves,
sometimes girdling the plant if they occur near the soil line
Survival and spread:Primary:
The pathogen overwinters in
infected plant debris in or on
the soil where it can survive
at least one and perhaps
several years. It can also be
seed borne.
Secondary:
The spores are transported by
water, wind, insects, other
animals including man, and
machinery.
Favourable conditions:
Warm, rainy and wet weather

11. Common scab
• Disease symptoms:
• Pathogen infects young developing tubers
through the lenticels and occasionally
through wounds.
• Symptoms of common potato scab are quite
variable and are manifested on the surface
of the potato tuber. The disease forms
several types of cork-like lesions including
surface.
• Damaged tubers have rough, cracked skin,
with scab-like spots. Severe infections leave
potato skins covered with rough black welts.
• Initial infections result in superficial reddish-
brown spots on the surface of tubers. As the
tubers grow, lesions expand, becoming corky
and necrotic.
Survival and spread:
Pathogen can survive in soil,
uncomposted manure or seed
It spreads through contaminated
soil, seed and water.
Favourable conditions:
Disease is common in fields with
low soil pH favoured by high soil
moisture.
Disease problems may be
aggravated by excessive
irrigation.

12. Black scurf/
canker
Disease symptoms: Rhizoctonia canker occurs
when stolons contact soil borne fungal bodies.
Pathogen infects plant tissue and causes stolon
blinding thus reducing tuber production and
yield.
It also infects tubers causing black scurf but
this is purely cosmetic, reduces tuber
appearance and does not reduce yield.
Survival and spread:
Pathogen is soil and seed borne, remain
in soil and plant debris including infected
tubers
Favourable conditions:
High temperature and moisture is the
favourable for disease development

13. 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
Bacteria are carried on tubers and in wounds and can be
spread to healthy tubers during handling and cutting of
seed pieces; disease emergence favors high soil
temperatures
Management
Plant seed pieces which are the product of tissue
culture;
sanitize tools and equipment when cutting seed pieced
to prevent bacterial contamination;
avoid damaging tubers during harvest;
 reduce periods of leaf wetness by allowing enough time
for leaves to dry throughout the day after watering

14. Viral disease (potato virus X, S, & Y)
 Disease symptoms:
 Potato virus Y (PVY ) is a Potyvirus, causes stipple streak. The necrotic strain
generally causes mild foliage symptoms, but necrosis in the leaves of susceptible
potato varieties.
 Potato virus S (PVS) is a Carlavirus, if plant infected early in the season, show a
slight deepening of the veins, rough leaves, more open growth, mild mottling,
bronzing, or tiny necrotic spots on the leaves. PVS is transmitted by aphids non-
persistently.
 Potato virus X (PVX) is the type member of the Potyvirus family of plant viruses.
Plants often do not exhibit symptoms, but the virus can cause symptoms of
chlorosis, mosaic, decreased leaf size, and necrotic lesions in tubers.
 PVX can interact with PVY and PVS to cause more severe symptoms and yield loss
than either virus alone. The source of this virus is infected tubers.

15. Cutworms Agrotis spp.
 Cutworms will curl up into a characteristic C shape when disturbed
 Symptoms
 Stems of young transplants or seedlings may be severed at soil line; if
infection occurs later, irregular holes are eaten into the surface of fruits;
larvae causing the damage are usually active at night and hide during the day
in the soil at the base of the plants or in plant debris of toppled plant; larvae
are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and
coloration but will usually curl up into a C-shape when disturbed
 Cutworms have a wide host range and attack vegetables including
asparagus, bean, cabbage and other crucifers, carrot, celery, corn, lettuce,
pea, pepper, potato and tomato
 Management
 Remove all plant residue from soil after harvest or at least two weeks
before planting, this is especially important if the previous crop was another
host such as alfalfa, beans or a leguminous cover crop;
 plastic or foil collars fitted around plant stems to cover the bottom 3
inches above the soil line and extending a couple of inches into the soil can
prevent larvae severing plants;
 hand-pick larvae after dark;
 spread diatomaceous earth around the base of the plants (this creates a
sharp barrier that will cut the insects if they try and crawl over it).

16. Aphids (Peach aphid, Potato aphid)
Myzus persicae, Macrosiphon euphorbiae
Small soft bodied insects on underside of leaves and/or stems of plant;
usually green or yellow in color, but may be pink, brown, red or black
depending on species and host plant; if aphid infestation is heavy it may
cause leaves to yellow and/or distorted, necrotic spots on leaves and/or
stunted shoots; aphids secrete a sticky, sugary substance called
honeydew which encourages the growth of sooty mold on the plants
Aphids are most damaging to potato through the transmission of viruses
such as Potato leafroll virus; distinguishing aphid features include the
presence of cornicles (tubular structures) which project backwards from
the body of the aphid; will generally not move very quickly when
disturbed
Potato beetle Leptinotarsa decemlineata
Feeding damage to foliage; if infestation is severe or if left untreated plants
can be completely defoliated; adult insect is a black and yellow striped
beetle; larvae are bright red with black heads when they first hatch and
change color to pink; larvae have two rows of black spots
Adult beetles emerge in spring; female beetles lay eggs in batches of up to
two dozen; eggs are orange-yellow and are laid on undersides of leaves; a
female can lay 500 or more eggs over a four to five week period
Management : Applications of Bacillus thuringiensis can be effective at
controlling larvae but should be applied frequently; some insecticides,
including spinosad, are still effective

17. POTATO IPM
• Pre sowing*
• Summer deep ploughing
• Soil solarization during summer.
• Field sanitation, rogueing.
• Avoid water logged conditions in
the field.
• Follow crop rotation.
• Apply manures and fertilizers as
per soil test recommendations
Biological control:
• Apply neem
cake@ 80 Kg/acre.
Bacterial
wilt
Cultural control:
• Use pathogen free tubers.
• Disinfect the cutting knife using 1% sodium
hypochlorite solution.
• Apply lime (dolomite) in the soil as acidic or alkaline
soil is not conducive to the
bacterial wilt pathogen.
Biological control:
• Apply neem cake @ 80 Kg/acre
Chemical control:
• Two to three sprays of (streptomycin sulphate 9% +
tetracylin hydrocloride 1%) SP @
40 to 50 ppm solution at an interval of 20 days. First
spray 30 days after planting.
Chemical control:
• Spray captan 50% WG @ 600 g in 200 l water (second spray after 5 days interval) or captan 50% WP @ 1 Kg in 300- 400
l water/acre or captan 75% WP @ 666 g in 400 l water/acre (second spray after 8 days interval) or chlorothalonil 75%
WP @ 350-500 g in 240-320 l of water/acre (second spray after 14 days interval) or copper oxychloride 50% WP @ 1 Kg
in 300-400 l of water/acre or copper sulphate 2.62 % SC @ 400 ml in 200 l of water/acre (second spray after 3 days
interval) or cyazafamid 34.5% SC @ 80 ml in 200 l water/acre (second spray after 27 days interval) or dimethomorph
50% WP@ 400 g in 300 l water/acre (second spray after 16 days interval) or mancozeb 75% WG @ 400 in 200 l
water/acre (second spray after 3-5 days interval) or mancozeb 75% WP@ 600-800 g in 300 l water/acre or hexaconazole
2% SC @ 1.2 l in 200 l water/acre (second spray after 21 days interval) or mandipropamid 23.4% SC @ 0.2 ml/ l in 200-
300 l of water/acre (second spray after 40 days interval) or propineb 70% WP @ 300 g in 100 l of water or 0.30% as
required depending upon crop stage and plant protection equipment used (second spray after 15 days interval) or zineb
75% WP@ 600- 800 g in 300-400 l of water/acre or captan 70% + hexaconazole 5% WP @ 200- 400 g in 200 l of
water/acre (second spray after 21 days interval) or cymoxanil 8% + mancozeb 64% WP @ 600- 800 g in 200-300 l of
water/acre (second spray after 10 days interval) or famoxadone 16.6% + cymoxanil 22.1% SC @ 200 ml in 200-300 l of
water/acre (second spray after 27 days interval) or fenamidone 10% + mancozeb 50% WDG @ 500- 600 g in 200 l of
water/acre (second spray after 30 days interval) or metalaxyl M 4% + mancozeb 64% WP @ 025% 1 Kg/ acre in 200-400
l water (second spray after 24 days interval) or metalaxyl 8% + mancozeb 64% WP @ 025% 1 Kg/ acre in 400 l water
(second spray not less than7 weeks) or metiram 55% + pyraclostrobin 5% WG @ 600-700 g in 200 l water/ acre (second
spray after 15 days interval) or azoxystrobin 23% SC@200 ml in 200 l of water/acre or treat tuber with carbendazim 25%
+ mancozeb 50% WS @ (1.5 + 3.0) to (1.75 + 3.5) for 10 Kg seed (tuber).