This document discusses various methods for controlling plant diseases. The major methods discussed are cultural control methods, biological control methods, and chemical control methods. Cultural control methods include avoiding contact between the pathogen and host plant through proper field selection, resistant varieties, and modifying cultural practices. Biological control uses other organisms like fungi, bacteria, and mycorrhizal fungi to control pathogens. Chemical control involves the use of fungicides, bactericides, and other chemical treatments to directly kill or inhibit pathogens.

1. PLANT DISEASE CONTROL
SAMPATH KUMAR BANOTH
.
MSC
.
DEPARTMENT OF MICROBIOLOGY
KAKATIYA UNIVERSITY
WARANGAL-506009

2. INTRODUCTION:
• Plant disease control is emient process in crop yeilding
without complete or partial eradication of pathogen,or control
measures of disease,one cannot get good crop yeild results
without proper control ammendments of disease or
pathogen.
• Although there are several articals and books on
management of plant diseases, one of the recent decade
articles entitled “advances in plant health management in
20th centuary” by cook in 2000.
• The major aspect of plant disease is to “eliminate or
eradicate the pathogen from plant / crop, pre or post harvest
to control the disease and loss of crop yeild by the pathogen.”

3. •Various methods are being followed for controlling
the diseases in plants, though the principle and
basic theme of plant disease control is similar in all
methods which include.
1)AVOIDENCE
2)EXCLUSION
3)ERADICATION
4)PROTECTION
5)IMMUNIZATION

4. • METHODS USED IN PLANT DISEASE MANAGEMENT :
 1) CULTURAL METHODS
 2) BIOLOGICAL CONTROL METHODS
 3) BREEDING METHODS FOR DISESE
RESISTANCE
 4) CHEMICAL METHODS
 5) PLANT DISEASE ASSMENT METHODS
 6) POST HARVEST DISEASE CONTROL

5. CULTURAL METHODS :
 Stevans (1960) had discovered the cultural methods of disease control
according to him, these measures involve agricultural croping,
harvesting and storage, tillage, crop rotation, soil management, growing
of resistant varieties, planning of land use, and other related practices.
 1. AVOIDENCE OF PATHOGEN :
 Diseases can be prevented by a proper selection of the land or field,
choice of time of sowing, selection of varieties, seed and plant stock and
by modification of cultural practices.
 The aim of these measures is to enable the host to avoid contact with
the pathogen or to ensure that the susceptible stage of the plant and
favorable conditions for the pathogen not coincide.
 2.PROPER SELECTION OF GEOGRAPHICAL AREA :
 Many fungal & bacterial diseases are more severe in wet areas than in
dry areas, crop which are susceptible to these diseases, if grown in wet
areas are likely to be effected by plant pathogens.
 Eg; smut disease of bajra caused by TOLYPOSPORIUM
PENCILLARIAE.

6. 3. SELECTION OF FIELD
 The selection of suitable area or field for cultivation is very important
from the point of view of better yeild’s, as well as protection of the crop
from the ravages in the case of many soil borne pathogens, Hence it is
advisible not to grow in the same field, where there is high incidence of
disease appearing, due to build-up of innoculm potential.
 Eg; the drinage conditions of the field are also important , low lying, water
logged fields favour such diseases as red rot of sugarcane and downy
mildews of bajra. In case of fruit orchards the selection of suitable site is
very important
4. CHOICE OF TIME OF SOWING :
 Pathogens are able to infect susceptible plants only under certain
environmental conditions. Eg; Rhizoctina root rot of gram is severe if
gram is sown immediately after the rains, due to the pathogen devlops
rapidly under high temperate and moisture conditions.
5. DISEASE ESCAPING VARITIES
 Certain varieties escape the onslaught of the pathogen and resist the
attack due to their inherent charecteristic’s. Eg; maturing varieties of
wheat or pea escape damage due to Puccinia Graminis Tritici and
Esiphe Polygoni respectively.

7. 5. DISEASE ESCAPING VARITEIS
Certain varieties escape the onslaught of the pathogen and
resist the attack due to their inherent charecteristic’s. Eg;
maturing varieties of wheat or pea escape damage due to
Puccinia Graminis Tritici and Esiphe Polygoni respectively.
6. SELECTION OF SEED AND PLANTING STOCK :
since many plants propagate by vegitative parts, the
selection of diseases free planting material, forms a very
important control measures.The planting of disease-free
fields is often an important control measures for certain
diseases such as red rot of sugar cane and black scruf of
potato etc.

8. MODIFICATIONS OF CULTURAL PRACTICES
• The distance between plants, time and amount of
irrigation ,quantity and quality of fertilizers or
organic manures, time and method of planting,
mixed croping method, depth of sowing, & so on
are some cultural practices which influence the
incidence and severity of certain diseases.
For eg; tillage, mixed croping
,management of soil water offers a means to
manage the associated microbiota directely
through water potential and indirectely through gas
exchange of the soil.

9. HERE ARE SOME MODIFICATIONS :
• 1. exculsion of innocullum.
• 2. seed treatment -> heat, gas, or chemical.
• 3. inspection and certification.
• 4. qurantine regulation -> domestic, internal, total, embargoes,
• First regulated in usa in 1912 known as federal qurantine acts.
– In india 1914,as destructive insect and pest act.
– In 1951 rome a international plant protection conversion was
drawn up which at present has 50 signatory nations.
• 5. eradication of pathogen -> works on brekage of infection chain.
• 6. roughing -> careful removal of infected plant or parts from field
@an entry stage (removing of foci)
• 7. eradication of alternate or collateral host.
• 8. crop-rotation
• 9. sanitation.
• 10. heat or chemical treatment of diseased plants.
• 11. soil trement.

10. BIOLOGICAL CONTROL METHODS
• The term biological control clearly implies control of a disease
through some biological agency, and the term biological agency,
means a living micro organism or macro organism other than the
diseased or damaged plant acting as host and the pathogen or pest
causing the disease or damage.
• According to Garrett (1965) “ biological control of plant disease may
be defined as any condition or practice whereby survival or activity
of a pathogen is reduced through the agency of any other living
organism ( except man himself), with the result that there is a
reduction in the incidence of the disease caused by the pathogen”.
• Eg: Trichoderma viride, a common saprophytic fungus, is able to
parasitize the mycelia of other fungi.

11. DIFFERENT MECHANISMS HAVE BEEN PROPOSED TO EXPLAIN
DISEASE SUPPRESSION BY PSEUDOMONAS SPP. THEY INCLUDE :
1. Production of siderophores ( iron chelating compounds) which
remove iron from the soil environment and make it unavailable to
pathogens.
2. Anti biosis –various anti biotics have been reported to be produced
by members of genus Pseudomonas.
3. Induction of resistance, and
4. Competitive root colonization.
• MYCORRHIZAL FUNGI AS BIO CONTROL AGENTS:
• Mycorrhizal fungi have received considerable attention in recent
years, the role of these agents of fungal root pathogens is well
known ( reid, 1900,Chandra 1992). Several mechanisms have
been postulated. These are :

12. 1. Creating a mechanical barrier for the pathogen to penetrate,
2. Inducing thickening of cell walls through lignification and
production of other polysaccharides,
3. Stimulation of host roots to accumulate metabolites,
4. Stimulating flavanolic wall infusions,
5. Increasing concentrations of dihydroxy phenols in roots,
6. Producing anti bacterial and anti fungal anti biotics, and
7. Stimulating microbial activity in the root zone.
SOIL AMENDMENTS:
Many root diseases such as potato scab have been controlled by
ploughing organic material into the soil,
The organic amendments increase the activity of saprophytic
organisms in a flush which results in the abundant liberation of
Co2 as a result of the respiratory activity of the microbes. The
pathogens sensetive to Co2 are inhibited. Due to the rapid
multiplication of microbes in the soil, the available nitrogen in the
soil is rapidly utilized by the fast growing saprophytes.
.

13. • This results in acute nitrogen scarcity which adversely affects the
growth of the pathogens.
• Maurer and baker (1965) showed that c/n ratios greater than 25/1
significantly suppress symptoms of been root rot.
• Biological control in potato diseases of underground parts has been
studied by shrivastava and saksena (1968).
• HYPERPARASITISM ;
• Certain fungi and bacteria are parasitic on plant pathogens.
• Several workers have tried to utilize eudarluca australis (pycinidial
stage known as darluca filum) for controling rusts.
• Many fungi are known to parasitize phyto pathogenicnematodes.in
1934 rozsypal and schmidt reported a protomycopsis chytridiale
which attacks heterodera schachitti.
• BACTERIOPHAGES :
• In 1917 d’Herelle presented evidence of a transmissible lytic principle
that acted on the shiga bacillus, showing that bacteria have their
infective diseases too. A number of phages have now been discovered
for many phytophatogenic bacteria such as agrobacterium
tumefaceians etc but no plant disease has been cured yet by treatment
with phage after the diseases has developed.

14. ENTOMOGENOUS FUNGI :
• There are several fungi ,which are capable of growing in the bodies
of insects thus destroying them . Scientists are looking for ways of
protecting crops against insect pests .in late 1940 with the
introduction of DDT, it was felt that a method had been found to
destroy insects affecting crops.
• One important fungus which has been utilized is entomphthora,
about 011 spp are known, mostly as insect parasites.
• CHEMICAL METHODS :
• Plant diseases play an important role in determining the amount
and cost of food. plant pathology must alleviate the food problem
by devising new control measures and improving the older ones.
• The use of chemical sprays , dusts or seed treatment for protecting
plants from the ravages of pathogens is not an innovation of 20th
century.
• The first landmark in the control of fungal diseases of plants was
discovery by anton and debary that the causal agents of many plant
diseases are fungi.

15. •The fungicides used on plants may be classified as,
1. Protectants
2. Eradicants
3. Therapeutants
• On the basis of their uptake by mobility within plants.
• The fungicides are dealt with below under the following catagories;
1. Inorganic copper compounds
2. Inorganic mercury compounds
3. Sulphur sprays
4. Organic sulphur compounds
5. Quinone and phenolic fungicides
6. Hetrocyclic nitrogen compounds
7. Benzene compounds
8. organomercurials
9. Systemic fungicides
10. Organophosphate fungicides
11. Antibiotics
12. Soil fumigants
13. oils

16. BREEDING FOR DISEASE RESISTANCE :
• The use of disease resistant varieties for controlling plant diseases
has been termed the “painless method” because it does not cost
the farmer anything.
• The use of resistant cultivars and hybrids has several other
advantages it eliminates the hazards to human health and wild life
which is caused by large scale use of dangerous fungicides and
pesticides it also reduces pollution which results from the use of
poisonous chemicals and their residues, resistant crop varieties
check epidemics of pathogens and pests and thus help to maintain
the biological balance environment.
• A very superior variety of hops (humulus lupulus) was cultivated in
western europe. In 1917. taichung native 1 etc.

17. TYPES OF RESISTANCE :
• Plant pathologists commonly divide resistance into monogenic,
Poloigenic, and Oligogenic according to wether the resistance is
governed by one or many genes, or a few genes resistence can be
discribed as genetic, machanical or epidemilogical.
• Oligogenic resistance is determined by 2 to several genes
• Polygenic resistance involves many genes which are more difficult
to analyse and which are known to be included in a large no of
diseases such as cotton wilt.
FEW STEPS INCLUDED :
• Extra chromosomal inheritance
• Gene interaction
• Modifier genes
• Reversal of dominance

18. • Concept of vertical and horizontal resistance
• Methods of selection of resistant geno types
• Selection from existing crops
1. Selection from crops that escape damage in infected
fields
2. Pure line selection
3. Plant introduction
4. Hybriedization
5. Selection from wild verities
6. Induced mutations

19. POST HARVEST CONTROL METHODS
1. Post harvest diseases types
• Bacterial Rots
• Fungi
• Non Pathogenic Diseases
CULTURAL METHODS TO CONTROL P.H.D.C.
• Harvesting and Handling
• Packaging
• Transportation
• Storage
• Temperature and Relative Humidity
• Control of Pre Harvest Infection

20. STRATEGIES FOR POST HARVEST DISEASE CONTROL
1. Orchard Management
2. Disinfection and Washing
3. Post Harvest Chemical Treatment
4. Fumigation
5. Fruit Wraps, Waxing, Coating and Packaging
6. Heat Treatment
7. Irradiation
8. Low Temperature Storage
9. Controlled Temperature storage
10. Maintenance of Host Resistance
11. Moderation of Disease Symptoms
12. Chemical Treatments, Etc.

21. • thankyou