Plant disease symptoms converted

Made by Vijay kumar Arya
Department of Agriculture
Uttrakhand
1

PLANT DISEASES:
1. A plant disease can also be defined as any problem with
the plant that leads to a reduction in yield or appearance.
2. Many plant diseases are caused by pathogens disease
causing agents are called pathogens.
3. A plant may be said to be diseased, when there is harmful
deviation from normal functioning of physiological
processes.
2

CONDITIONS NECESSARY FOR
PATHOGENIC DISEASES:
❑ In order for a pathogenic plant disease to occur, three
conditions must be met:
1. The host plant must be susceptible.
2. An active , living pathogen must be present.
3. The environment must be suitable or favorable for disease
development.
❑ All three factors must occur simultaneously. If one
factor is absent or unfavorable , disease does not occur.
4

❑The more the circles overlap , the more severe will be
the disease.
❑Environmental factors such as temperature, light , or
moisture can accentuate diseases.
5

DISEASE CYCLE:
❑ The sequence of events from a pathogen’s survival to plant
disease development and back to pathogen cycle is called the
disease cycle, or the pathogen’s life
history.
❑ By understanding the disease cycle – chain of events that
contribute to a disease – we can find the weakest links and
take measures to break the cycle.
❑Most pathogens must survive a period of adverse conditions
, usually winter , when they do not actively cause disease.
❑ The host plant is infected or continues to be infected by
pathogen’s overwintered disease-transmitting substance ,
inoculum , in the spring.
6

1-Infection Plant Diseases - These are the diseases
caused by pathogenic organisms or viruses under a set
of environmental conditions. Example Fungi ,
bacteria , viruses , nematodes & even some plants can
be pathogens.
2- Non infection Plant Diseases - They are not
associated with any animate or viral pathogen , so
they cannot be transmitted from an infected plant to a
healthy one. Examples Low/high temperature,
unfavorable oxygen levels, unfavorable water levels,
hail , wind, air pollution toxicity etc.
7

1. Mildews : White , grey ,brownish ,or
purplish patches of varying sizes on leaves ,
herbaceous stems or fruits.
.
Powdery Mildew Downy Mildews
8

2. Rusts: Relatively small pustules of spores ,usually
breaking through the host epidermis.
Rusts 9

3. Smuts: In plant diseases known as smuts , the affected
parts of the plant show a purplish black or black dusty mass.
Smuts 10

4 White blisters: White blister-like pustules which
break open & expose powdery mass of spores.
White blisters- 11

5. Scab: Scab refers to a roughened or crest-like lesion or to
a freckled appearance of a diseased organ.
Scab
12

6. Sclerotia : Sclerotium is a compact, often hard mass of
dormant fungal mycelium. Sclerotia are most often black.
They may be sometimes buff or dark brown or purplish in
colour.
Sclerotia 13

7. Blotch :It is a superficial growth giving the fruits a
blotched appearance as in sooty blotch & fly-speck disease of
apple fruits.
Blotch 14

8-Fruiting bodies : They are large, fleshy or woody,
spore bearing structures, developed by woodrotting fungi.
Fruiting bodies 15

9.Tar spots : These are somewhat raised, black-coated
fungal bodies with the appearance of a flattened drop of tar on
the leaf.
Tar spots 16

❑ NON INFECTIOUS PLANT DISEASES-
High Temperature Unfavorable Oxygen levels
Unfavourable Water levels Hail
17

Lightning Injury Wind Damage
18

SYMPTOMS DUE TO SOME
EFFECT ON THE HOST PLANT:
❑ Diseases cause marked changes in the form , size , colour , texture ,
attitude or habit of the plant or some of its organs.
❑ Two or more of these changes may occur in the same host organ as
effects of the same disease.
❑ These changes result from the presence & activity ofsome pathogenic
organisms & also from the reaction of the host tissues against them.
❑ The pathogen may be found within the affected tissues or upon the
surface.
19

❑ Colour Changes : Discoloration of the plant , or change
of colour from normal colour.
❑ Example :
1) Chlorosis : Green → Yellow
2) Albinism : Green → Colourless
3) Chromosis : Green → Red , purple or orange
Chlorosis
20

❑ Overgrowth: Abnormal increase in the size of one or
more organs of the plant or certain portions of it.
1.This is usually the result of stimulation of the host tissues for
excessive growth. It may be due Hyperplasia or Hypertrophy.
❑Hyperplasia: Abnormal increase in the size of a plant
organ due to increase in the number of cells.
❑Hypertrophy: Increased size of the organ due to increased
size of cells.
❑ Atrophy or hypoplasia: Here inhibition of growth
occurs , resulting in stunting or dwarfing.
❑Dwarfing results from atrophy or hypoplasia:
Atrophy is degeneration of cells and organs, where as
hypoplasia is the abnormal decrease in the size of cells
& organs.
21

❑ Necrosis : It is the death of tissues & organs due to parasitic activity.
Necrotic symptoms are highly variable.
❑ Wilts : It is the drying or wilting of the entire plant. The leaves &
other green or succulent parts lose their turgidity, becomes flaccid
&droop. This effect is usually seen first in some of the leaves.
❑Die-back : It is the dying of plant organs, especially stem or branches ,
backwards from the tip.
Necrosis Wilts Die-back 22

❑ PLANT DISEASE CONTROL
❑Exclusion
❑Eradication
❑Protection
❑Immunization
23

❑ EXCLUSION: This method includes quarantines, inspections &
certification.
1.These techniques prevent movement of diseased plant material into a
particular country , state .
2. Quarantines are regulations forbidding sale or shipment of plants or
plant parts.
❑ AVOIDANCE: If a disease doesn’t occur in your area , you may be
able to avoid its development on your plants.
1. Planting certified , virus-free stock is a good way to avoid viral
diseases.
2.Root rots can be avoided by not planting in heavy poorly drained soils.
3. Delaying planting until soils are dry & warm can avoid damping-off of
vegetable seeds.
4.Avoid wounding plants when pruning or using equipment , as wounds
can be the entry points for pathogens or can weaken the plant so that it
cannot defend itself.
5. Use good horticultural practices, such as proper fertility , pruning ,
watering to ward off infections. 24

❑ERADICATION:
1. Rotation , sanitation , elimination of alternate hosts , chemical
application & heat treatment are eradication methods , when a plant is
infected or an area is infested with a pathogen.
2. Crop Rotation : It is common in both commercial & home gardens ,
involving planting of different crops in a given location each year. It can
reduce soil
❑SANITATION: Removing plant debris , is important where pathogens
may overwinter.
I. Rake leaves , remove rotted fruit , pick up old vines & prune out dead
wood or canes.
II. Dispose of the debris by burning burying or hot composting.
ELIMINATION OF ALTERNATE HOSTS : Certain pathogens complete
their life cycle on two or more hosts (E.g.: Rusts) only one of which may
be a crop plant. Eliminating alternate hosts may reduce pressure from
these diseases , Since such pathogens cannot complete their life cycle
without the alternate host.
25

Infections & Infestations can be prevented by certain chemicals .
Some fungicides also have kickback action.
Certain fungi & nematodes can be reduced by fumigating or steam
sterilizing the soil.
Heat treatment is usually used to eliminate viruses from propagation
material.
Solarization
Steam
treatment of
soil
27

❑RESISTANCE:
❑Resistance , immunity , tolerance & susceptibility are the terms that
describe a plant’s genetic makeup & its reaction to plant pathogens.
Resistance & its opposite , susceptibility , are levels or degrees of a
plant’s reaction to a pathogen.
If a plant never becomes diseased , the term immune is used.
The word tolerant describes a plant which may become diseased yet
grow much like a healthy plant.
Planting resistant cultivars is the easiest means of disease control.
28

29
❑ Bacterial Disease Resistance in Plants: Molecular Biology and
Biotechnological Applications Author Perumal Vidhyasekaran
❑ Plant PathologyGeorge Author Nicholas Agrios
❑Plant disease Dr. R.S. Singh
❑https://www./plant-diseases-70573937
❑www .google .com

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