PRINCIPLES OF PLANT DISEASE MANAGEMENT AN OVERVIEW ON ERADICATION

2. RANI LAKSHMI BAI CENTRAL AGRICULTURAL UNIVERSITY
JHANSI, U.P
Subject:Principles of Plant Disease Management.
APP 506 [2+1]
Topic:Presentation on Principle 'Eradication'.

3. Submitted to,
Dr.Sunaina Bisht,
Teaching Associate,
Department of Plant Pathology,
RLBCAU,Jhansi.
Submitted by,
Bhargavi G. Ag/Pg/0019/19
Harish J. Ag/Pg/0020/19
First year M.sc Agri(Plant Pathology),
Department of Plant Pathology,
RLBCAU,Jhansi.

4. Management
Concept of continuous process which is based not
only on the principle of eradication of the pathogen
but mainly on the principle of minimizing the damage
or less below economic injuiry level.
Principles of Disease management
1.Exclusion
2.Avoidance
3.Eradication
4.Immunization
5.Protection
6.Therapy

5. Eradication
Reducing,inactivating,eliminating or destorying inoculum at
the source either from a region or from an individual plant
in which is already established.
Many different types of control methods aim at
1. Breaking the infection chain by removing the
infection and starvation of the pathogen.
2.Reducing the amount of pathogen present in an area,a
plant or plant parts.
Basically it includes Cultural methods , Physical
methods,Biological methods,Chemical methods.

6. Cultural methods
1.Host eradication
2.Crop rotation
3.Sanitation
4.Eradication of Alternate host,
collateral hosts and wild plants
5.Eradication by Surgery
6.Mixed cropping
7.Summer ploughing
8.Burning of stubbles and crop residues
9.Polyethylene traps and mulches
10.Creating conditions unfavourable to the pathogen.
11.Barrier cropping
12.Intercropping
13.Decoy and Trap crops
14.Trenches
15.Adjusting Depth and Date of Sowing.

7. Cultural methods
Host Eradication
a. Disease plants or their part should be sorted out after inspection
and eradicated.
b. If the disease is quite severe,entire crop should eradicated or
destroyed.
c. Periodical inspection of crops is the primary requirement
d. Diseased-host eradication results in reduction of inoculum density
in the field or complete elimination.
Ex:1) Elimination of Citrus canker caused by Xanthomonas
campestris pv citri from USA,nearly 20 million diseased
citrus plants [1914 &1934].
2) Whip smut of Sugarcane,Loose smut of wheat and barley,
Khatte disease of cordamom.

8. Crop rotation
• Most of the soil borne diseases can be effectively managed by employing
crop rotation.
• Sucess of the crop rotation depends on proper selection of crops in
sequence & knowledge about method of survival.
• Satisfactory control on Soil invaders(survive only in living plants).
• Less effective on soil inhabitants(produces long lived spores or live as a
saprophyte(>5 or 6 years)
Two main considerations of Crop rotation are
1. The crop grown between the susceptible host crops should
be resistant or immune to the pathogen.
2. It should be non host &their root exudates should not
directly or indirectly favours the survival of the pathog
Ex:1)Red rot of sugarcane(Collectotrichum falcutum) persists in soil for
few months. Therefore sugarcane should not be grown in
subsequent season.
2)Fusarium oxysporum f.sp.vasinfectum,Claviceps ,Tolysporium
pencilliariae

9. Sanitation
Aims at all activities aimed at eliminating or reducing the amount of inoculum
present ina plant/field for preventing the spread of the pathogen to other
healthy plants.
• Pruning of infected plants or infected branches.
• Removal and proper disposal of infected plant debris.
• Washing the produce,its containers and the walls of storage houses
• Washing the soil from field equipments before moving from one field to
another field.
• Ex:Fusarium wilt of cotton,pigeonpea and banana,Verticillium wilt of
cotton,root rot of beans,downy mildew of pearlmillet,sorghum, maize and
peas,foot rot of betelvine,bacterial blight of cotton, white rust of crucifers.

10. Eradication of Alternate,Collateral and wild hosts
• Barbery eradication reduced the severity of black stem rust of wheat.
• Eradication of Thalictrum species to manage leaf rust of wheat.
• Eradication of colateral hostssuch as Panicum repense,Digitaria marginata
will help in the management of Rice blast.
• Cucumber mosaic virus overwinters mainly on perennials(wild),Eradication
of the wild host to eliminate the pathogen completely.

11. Thalictrum app.
Collateral hosts of Rice blast

12. Eradication of infected plant parts by Surgery
• Eradication of affected plant parts( tree surgery) are also practiced in certain cases
which reduces the source of primary inoculum.
• This not only prevents further spread in the affected trees but also reduces the
amount of inoculum that can spread to other branches and trees.
• Eg:Lesions caused by fire blight bacterium (Erwinia amylovora) on pear and apple
trees are removed during winter months.
• coconut trees affected by stem bleeding disease (Ceratocystis paradoxa),
• citrus gummosis (Phytophthora citrophthora), Dendrophthoe spp. on citrus,
• bud rot of palms (Phytophthora palmivora) and koleroga of arecanut (P.arecae)

13. Eradication of infected plant parts

14. Summer ploughing
Ploughing the soil during summer months expose the soil to hot
weather which will eradicate heat sensitive soil borne pathogens.
Ex:1.Groundnut blight (Corticium rolfsii) is controlled by
ploughing the soil to a depth of 20 cm.
2.The inverted plough sole soil buries the sclerotia
of the fungi, Claviceps, Sclerotium and Sclerotinia.

15. Summer ploughing

16. Burning of stubbles and crop residues
• Burning of plant wastes, crop residues, stubbles, etc., in the areas
selected for raising nurseries for vegetable crops, tobacco, chillies and
forest trees etc. heats the soil and kills the inoculum of the pathogens
present in the top layer of the soil.
• Eg: Burning of Wheat plant for eradication of pathogen in the field
when Cephalosporium gramineum infects wheat
• Burning of rice crop residues avoid carryover of sheath blight
(Rhizoctonia solani); stem rot(Sclerotium oryzae) of rice and bacterial
blight of cotton.

17. Burning of stubbles and crop residues

18. Polyethylene traps and mulches
• Vertical,sticky yellow polyethylene sheets are erected along the
edges of susceptible crops,a number of aphids are attracted.
• Many plant viruses such as cucumber mosaic virus,which was
transmitted by aphids are controlled.
• It reduces the amount of virus inoculum reaching the crops.
• Yellow sticky traps are used for whitefly which reduces leafcurl
disease of cotton,Yellow vein clearing mosaic virus etc.

19. Sticky trap

20. Creating unfavourable conditions to the pathogen.
• Spacing in the field or green house prevents the high humudity
conditions reduces Botrytis and peronospora.
• Good soil drainage reduces the activity of oomycete fungi.
• Flooding fields for long period or dry fallowing may also reduce the
certain pathogens like Fusarium,Sclerotinia sclerotiorum,Nematodes.
• The appropriate choice of fertlizers or Soil amendments changes pH
which also reduce pathogen development..
Ex : 1.Apply lime (2500kg/ha) reduces clubroot of cabbage by
increasing soil pH to 8.5.
2.Application of sulphur (900kg /ha) to reduce the common scab
of potato by bringing soil pH to 5.2.
3.Ganoderma ,Root rot

21. Mixed cropping
• Root rot of cotton is reduced when cotton is grown along with
sorghum.
• Blight of pulse crop (Phyllosticta phaseolina ) has been
successfully overcome by growing pulses as a mixed crop with
cereals like sorghum and pearlmillet.
Trenching
• Trench between rows of trees in orchards used to arrest the
growth and spread of the pathogen in the soil to the
neighbouring trees.
• Ganoderma lucidum root rot infected citrus trees should be
isolated by digging a trench of 30 cm wide and 60 cm to 90 cm
deep around the tree at a distance of 2.5 to 3.0 m from the
base to prevent the contact of diseased roots with healthy roots.

22. Mixed Cropping

23. Trenching
To manage
Ganoderma
root rot

24. Barrier cropping
Taller crops can be grown to protect a crop of lesser height from
virus vectors.
The insects may land at taller crops and the dwarf crop may
escape from virus diseases by those insects.
Ex:
• Cropping with 3 rows of maize or sorghum or pearlmillet around
the crop blackgram or greengram is effective in reducing the
vector population and incidence of yellow mosaic.
• Growing of 3 rows of kale or barley as barrier crops in cauliflower
seed beds and undersown beet steckling against cauliflower
mosaic and beet yellows diseases respectively.

26. Intercropping
 A device in the control of some soil borne diseases.
• Intercrops should be properly chosen so that they should not have any
common pathogen for e.g., Macrophomina phaseolina has got wide host
range and hence common host should not be grown as intercrops.
Ex:Intercropping with moth bean (Phaseolus aconitifolius) in a cotton
field reduced the root rot (M.phaseolina) incidence.
• Intercropping of sorghum in pigeonpea field reduced the wilt
(F.udum)incidence.
• Intercropping of sorghum or mothbean in a crop of clusterbean reduced
the incidence of root rot (R.solani) and wilt (F.coeruleum).
• Intercropping of pigeonpea with gingelly at 1:6 ratio reduced the incidence of
phyllody disease.

27. Intercropping

28. Decoy crops
Decoy crops (hostile crops) are non-host crops sown with the
purpose of making soilborne pathogens waste their infection
potential.
This is effected by activating dormant propagules of fungi, seeds
of parasitic plants, etc. in absence of the host.

29. Decoy crop( Sunflower)

30. Trap crops
Host crops of the pathogen,sown to attract pathogens but destined to be
harvested or destroyed before they complete their life cycle.
Ex:
Fodder sorghum can be raised as a trap crop to reduce downy mildew of
sorghum.
Trap crop Pest controlled
Marigold Thrips, Nematode
Oats Cyst Nematode
Radish Root fly of Cabbage
Mustard Diamond back moth of
Cabbage
Flax Orabanche

31. Adjusting Depth and Date of Sowing
Depth of sowing greatly influences seed transmission of smuts.
Shallow planting in wet soils protects wheat plants from Urocystis
tritici (flag smut) of wheat.
Deep planting may cause delay in the emergence of seedlings,
which may be vulnerable to pre-emergence damping off.
Early emergence results in early lignification of tissues which
become resistant to attack of soil-borne pathogens.
Date of Sowing : Pathogens are able to infect susceptible plants
under certain environmental conditions. Alternation in date of
sowing can help avoidance of favourable conditions for the
pathogens.
Eg: Diseases like Tikka disease of Ground nut,Wilt of Pea and
Chickpea can be managed by late Sowing.
Diseases like Karnal bunt of Wheat,Stem rust of wheat,Downy
mildew of maize can be managed by Early Sowing.

32. Physical methods
1.Control by heat treatment.
a.Soil sterlization by heat.
b.Soil solarization.
c.Hot water treatment.
d.Hot air treatment.
2.Drying stored grains and fruits.
3.Control by Refrigeration.
4.Control by Radiation.
5.Control by Certain wavelength.

33. Physical methods
Control by heat treatment
1.Soil sterilization
• Soil can be sterlized in greenhouse or in seed beds.
• The heat is covered in aerarted steam or hot water.
• The soil is steam sterlized either in special containers or green house
benches.
• At 50°c - Nematodes,some oomycetes,water moulds are killed.
• 60°c-72°c- Fungi,bacteria,slugs,Centipedes.
• At 82°c-Weeds,Other bacterias,plant viruses,insects killed.
• Some heat tolerant seeds and viruses are killed at 95°c-100°c.

34. 2.Soil Solarization
• Clear polyethylene sheet placed over moist soil in
summer days.
• The temperature at the top 5cm of soil may reach 52°c
compare to a maximum of 37°c in unmulched soil
• Soil solarization is generally used for controlling soil-
borne pathogens like Pythium, Verticillium,
Rhizoctonia, Fusarium etc.

35. Soil Solarization

36. Hot water treatment
• Hot water treatment of certain seeds ,bulbs,nursery
stocks is used to kill the pathogens with which present
inside coat,bulbs etc.
• Effectiveness is based on the fact that dormant plant
organs can withstand higher temperature than pathigen
for a given time.
Ex:1.Hot water treament of wheat seeds at 52°c for 11
minutes.
2.Grassy shoot can reduced by treating setts at 52°c
for 30 minutes.

37. Hot air treatment
• Treatment of certain storage organs with warm air(curing) removes
excess moisture from their surfaces.
• It also helps in healing of wounds,preventing infection from weak
pathogens.
• Sweet potatoes at 28°c to 32°c for 2 weeks to heat wounds and
prevents infection of Rhizopus and soft rotting bacteria.
• Dry heat treatment of barley seed at 72°c for 7-10 days eliminates
leaf streak and black chaff causing bacterium Xanthomonas
campestris pv transluens.

38. Refrigeration
• Low temperature at or slightly above the freezing point checks
the growth and activities of all such pathogens causes post
harvest diseases.
• Most perishable fruits and vegetables should be transported
and stored in refrigerated vehicles and stores.
• Regular refrigeration is sometimes preceded by a quick hydro
cooling or air cooling to remove the excess heat carried in
them from the field to prevent development of new or latent
infections.

39. Refrigeration

40. Radiations
• Electromagnetic radiations such as ultraviolet(UV)light,X rays and y -rays as
well as particulate radiations have been studied in relation to
management of post harvest diseases of horticultural crops.
• Y rays controlled post harvest fungal infections in peaches, straw
berries and tomatoes.

41. Control by certain wavelength
• Alternaria, Botrytis, and Stemphylium are examples of fungi that
sporulate only when they receive light in the ultraviolet range (below
360 nm).
• We can control diseases on greenhouse vegetables caused by several
species of fungi by covering or constructing greenhouse with a
special ultraviolet (UV)-absorbing vinyl film that block the
transmission of light wavelengths below 390 nm.

42. Drying stored grains and fruits
• All grains, legumes, and nuts carry with them a variety and number of
fungi and bacteria that can cause decay of these organs in the presence
of sufficient moisture.
• If seeds and nuts are harvested when properly mature and then are
allowed to dry in the air or are treated with heated air until the
moisture content is reduced sufficiently (to about 12% moisture) before
storage.
• Many fruits can also be stored dry for a long time and can be kept free
of disease if they are dried sufficiently before storage .

44. Luthras solar energy treatment
The seeds are soaked in cold water for 4 hours in the forenoon on a
bright summer day.
• Followed by spreading and drying the seeds in hot sun for
four hours in the afternoon. Then, the seeds are again
treated with carboxin or carbendazin at 2g/kg and stored.
• This method is highly useful for treating large quantities of the
seed lots.

45. Biological Methods
1.Supressive soils.
2.Antogonistic Microorganisms.
a.Soil borne pathogens
b.Aerial pathogens
3.Through Antagonistic plants.

46. Biological methods
Biological control of pathogens, i.e., the total or partial destruction of
pathogen populations by other organisms, occurs routinely in nature.
Several diseases in which the pathogen cannot develop in certain
areas called suppressive soil,which are antagonstic to pathogens.
antagonistic microorganisms may consist of avirulent strains of the
same pathogen that destroy or inhibit the development of the
pathogen, as happens in hypovirulence and cross protection.

47. Supressive soils
• They develop much less and cause much milder diseases in other soils
• In most cases,one or several mo's antagonistic to the pathogen.
• Such antagonists produce antibiotics,lytic enzymes,competition for food,
direct parasitizing of the pathogen, do not allow the pathogen to reach
high.
• Numerous kinds of antagonistic mo's have been found to increase in
suppressive soils,Trichoderma, Penicillium, and Sporidesmium,
Pseudomonas, Bacillus and Streptomyces.
• Suppressive soil added to conducive soil can reduce the amount of
disease by introducing mo's antagonistic to the pathogen.
• Continuous cultivation (monoculture) of the same crop in a conducive
soil, after some years of severe disease, eventually leads to reduction in
disease through increased populations of mo's antagonistic to the
pathogen.

48. Antagonistic micro oraganisms
1.Soilborne pathogen
A) Mycelium,spores,sclerotia of oomycetes,rhizoctonia ,Sclerotinia,sclerotium
are invaded and parasitized(mycoparasitism) or are lysed(Mycolysis).
B) Trichoderma harzianum parasitize mycelia of Rhizoctonia and Sclerotium
and inhibits the growth of oomycetes.
C) Gliocladium virens parasites and antagonist of Sclerotinia sclerotiorum
D)Talaromyces flavus parasitizes Verticillium &controls wilt of egg plant.
Bacillus,Pseudomonas and Pantoea parasitize and inhibit Phytophthora,
Pythium.
E)Meloidogyne javanica and Pratylenchus sp. nematodes are parasitized by
the bacterium Pasteuria (Bacillus) penetrans.

49. Mycoparasitism

50. Aerial pathogens
• Many other fungi have been shown to antagonize and inhibit numerous
fungal pathogens of aerial plant parts.
• Chaetomium sp. and Athelia bombacina suppress Venturia inaequalis
ascospore and conidia production in fallen and growing leaves,
respectively.
• Darluca filum and Verticillium lecanii parasitize several rusts.
• Ampelomyces quisqualis parasitizes several powdery mildews.
• Tuberculina maxima parasitizes the white pine blister rust fungus
Cronartium ribicola.
Mechanism of action
they are generally attributed to one of four effects:
(1) Direct parasitism or lysis and death of the pathogen
(2) Competition with the pathogen for food
(3) Direct toxic effects on the pathogen by antibiotic substances
released by the antagonist.
(4) Indirect toxic effects on the pathogen by volatile substances,
such as ethylene, released by the metabolic activities of the
antagonist.

51. Control through Antagonistic Plants
• A few kinds of plants, e.g., asparagus and marigolds, are antagonistic
to nematodes because they release substances in the soil that are
toxic to several plantparasitic nematodes.
• When interplanted with nematode susceptible crops, antagonistic
plants decrease the number of nematodes in the soil and in the roots
of the crops.
Antagonistic
Plant
Plant
Compound
Pest
Controlled
Sorghum HCN Fusarium app.
Marigold α-terthienyl Nematode
Mustard Glucosinolate Nematode

53. Chemical methods
 Soil treatment with Chemicals.
 Fumigation.
 Disinfestation of warehouses.
 Control of Vectors.
 Seed treatment.
 Foliar application.
 Special method of applications

54. Chemical methods
• Chemical pesticides are generally used to protect plant
surfaces from infection or to eradicate a pathogen.
• They include soil treaments(Such as
fumigation),Control of insect vectors , Seed
treatment,foliar application,etc.

55. Soil treatment with Chemicals
• Fungicides are applied the soil as dusts,liquid drenches or granules to
control Damping off,Seedling blights and root rots.
• Fungicides used for soil treaments include
Metalyxl,Diazoben,PCNB,Captan and chloroneb.
• Most of soil treatments aimed at controlling Nematodes and the materials
used are volatile gases that penetrate the soil throughout.
• Frequently treated with chemicals for control
nematodes,Fusarium,Verticillium.

56. Soil treatment

57. Fumigation
• Most promising method to kill nematodes and other soil borne
pathogens.
• Chloropicrin,Methylbromide,Dazomet and metham sodium are some
fumigants.
• Majority of them are preplant fumigants,which are effective against wide
range of soil Mo's like Nematodes,many fungi,insects,certain bacteria.
• Nematicides used as soil fumigants are available as liquids,Emulsifiable
concentrates and granules.
• All nematicides are extremely toxic to human and animals should be
handled with great caution.

58. Nematicides

59. Control of insect vectors.
• Application of insecticides for the control of insect carriers of fungus
spores,bacteria and viruses.
• In case of virus,Mollicutes and fastidious bacteria in which insects are the most
important disseminating agents.
• Insect control has been helpful in controlling the spread of their diseases.
• Sucess in reducing virus transmission by insects has been achieved by interfering
with the ability of vector to aquire and to trasmit the virus rather than by killing
the insects.
• Control of Aphid borne viruses by oil sprays has been sucessful with some
viruses(Cucumber mosaic virus on cucumber and pepper,Potato virus Y on
Pepper.

60. Insecticides to control vectors

61. Disinfestation of warehouses
• Stored products can be protected from becoming infected by
pathogens left over in the warehouse.
• Cleaning thoroughly the storage rooms by removing and burning the
debris.
• The walls and floors are washed with bleach,a Copper sulphate
solution(1 pound in 5 gallons of water)or other sanitizing agent.
• Warehouses that can be closed air tight and RH should be nearly
100% while temperature in between 25°c to 30°c.

62. Disinfestation of Warehouse

63. Seed treatment
• Using fungicides on seed is one of the most efficient and economical
methods of chemical disease control. On the basis of their tenacity
and action, the seed dressing chemicals may be grouped as
• Seed disinfectant: Which disinfect the seed but may not remain
active for a long period after the seed has been sown
• Seed protectants: Which disinfect the seed surface and stick to the
seed surface for sometime after the seed has been sown, thus giving
temporary protection to the young seedlings against soil borne
fungi.
• The systemic fungicides are impregnated into the seeds to eliminate
the deep seated infection in the seeds.
• The seed dressing chemicals may be applied by (i) Dry treatment (ii)
Wet treatment and (iii) Slurry.

64. Seed treatment

65. Foliar application
• Spraying : This is the most commonly followed method.
Spraying of fungicides is done on leaves, stems and fruits.
Wettable powders are most commonly used for preparing
spray solutions. The most common diluent or carrier is water.
• Dusting : Dusts are applied to all aerial parts of a plant as an
alternative to spraying. Dry powders are used for covering
host surface.

66. Foliar application

67. Special method of applications
• Trunk Application / Trunk Injection : Adopted in Coconut gardens to
control Thanjavur wilt (Ganoderma lucidum).In the infected plant,
downward hole is made to a depth of 3-4” at an angle of 45 at the
height of 3‟ from the ground level with the help of an auger.Solution
is taken ina a bottle, inserted into holeand stopper is adjusted to
allow solution in drops.
• Root feeding : Also to control Thanjavur wilt.Active growing root is
given slant cut and inserted into polythene bag containing solution
and tied.
• Pseudostem injection : In Aspee baby sprayer the nozzle replaced by
leurlock system and aspirator needle No.16.Tip of needle is closed
and two holes are made in opposite direction.It is used to control
aphid vector (Pentalonia nigronervosa) in bunchy top of banana.

68. Trunk injection

69. Root feeding
Pseudostem injection