PLANT DISEASEPLANT DISEASE

“ “a series of visible and invisible responses of plant a series of visible and invisible responses of plant cells and tissues to a pathogenic microorganism or cells and tissues to a pathogenic microorganism or environmental factors that result in adverse environmental factors that result in adverse changes in the form ,function , or integrity of the changes in the form ,function , or integrity of the plant and may lead to partial impairment or death plant and may lead to partial impairment or death of the plant or its parts” of the plant or its parts”

Definition

CAUSES OF PLANT DISEASECAUSES OF PLANT DISEASE 1. Living (animate)1. Living (animate) 2. Non- Living (inanimate)2. Non- Living (inanimate)

CLASSIFICATION OF PLANT DISEASECLASSIFICATION OF PLANT DISEASE

1. on the basis of extent to which diseases are associated with 1. on the basis of extent to which diseases are associated with plant :plant :a) Localised diseasesa) Localised diseasesb) Systemic diseasesb) Systemic diseases

2. on the basis of mode of primary infection :2. on the basis of mode of primary infection :a) Soil-borne diseasesa) Soil-borne diseasesb) Air – borne diseasesb) Air – borne diseasesc) Seed- borne diseasesc) Seed- borne diseases

3. on the basis of kind of symptoms :3. on the basis of kind of symptoms :a) Rust b) Smut c) Mildews d) Root- dots e) Blights a) Rust b) Smut c) Mildews d) Root- dots e) Blights

f) leaf spots g) Wilts h) Cankers i) fruit – rots and etc…f) leaf spots g) Wilts h) Cankers i) fruit – rots and etc…

Disease Caused By FungiDisease Caused By Fungi

1)DOWNY MILDEWS1)DOWNY MILDEWS

Downy mildew refers to any of several types Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of of oomycete microbes that are obligate parasites of

plants. Downy mildews exclusively belong plants. Downy mildews exclusively belong to Peronosporaceae.to Peronosporaceae.

Development and severity depend greatly on the Development and severity depend greatly on the presence of a film of water on the plant tissue and on presence of a film of water on the plant tissue and on

high humidity in air during cool or warm periods.high humidity in air during cool or warm periods.

Bordeaux – 1Bordeaux – 1stst Fungicide Fungicide

It may destroy 40-90% of young plant It may destroy 40-90% of young plant heavy losses of heavy losses of crop yield .crop yield .

Downy Mildew Of Grapes ( Downy Mildew Of Grapes ( Vitis Vitis viniferavinifera))

Symptomatology:Symptomatology:# small ,pale yellow ,irregular spot on upper surface of leaf.# small ,pale yellow ,irregular spot on upper surface of leaf.

# downy growth of the sporangiosphore of the fungus appear on # downy growth of the sporangiosphore of the fungus appear on the underside of spots. White downy spore masses on the the underside of spots. White downy spore masses on the lower surface of the leaf.lower surface of the leaf.

#Later, infected leaf areas are killed and turn brown ; spots #Later, infected leaf areas are killed and turn brown ; spots often enlarge, unite or combine to form large dead areas and often enlarge, unite or combine to form large dead areas and finally result to defoliation.finally result to defoliation.

###berries become leathery ,distorted ,thickened , wrinkled #berries become leathery ,distorted ,thickened , wrinkled

and may die .and may die .

#Downy mildew rapidly kills highly susceptible #Downy mildew rapidly kills highly susceptible young bunches , but berries are immune well before young bunches , but berries are immune well before

pea-size.pea-size.

Etiology Etiology ::

Caused by Caused by Plasmopara viticola.Plasmopara viticola.

ControlControl:: *sanitation*sanitation

*use of Resistant Varieties (*use of Resistant Varieties (Several North American Several North American species show resistance to downy mildew (e.g. species show resistance to downy mildew (e.g. V. V. labruscalabrusca and V.  and V. rotundifoliarotundifolia) ) .) ) .

*Fungicidal Sprays – Bordeaux, Zineb & Mineb(0.2%), Captan *Fungicidal Sprays – Bordeaux, Zineb & Mineb(0.2%), Captan (0.2-0.5%),Metalaxyl with Copper Oxychloride(0.3%).(0.2-0.5%),Metalaxyl with Copper Oxychloride(0.3%).

**Automatic weather stations (AWS) monitor the vine canopy for leaf Automatic weather stations (AWS) monitor the vine canopy for leaf wetness, rainfall, relative humidity and temperature, critical to wetness, rainfall, relative humidity and temperature, critical to downy mildew.downy mildew.

Downy Mildew Of Downy Mildew Of BajraBajra

Symptomatology:Symptomatology:# the infected plants are dwarfed because of shortening of # the infected plants are dwarfed because of shortening of

internodes & tillering is excessive. internodes & tillering is excessive.

# the foliage become pale & chlorotic & on the underside # the foliage become pale & chlorotic & on the underside covered by sporangia. Leaves become distorted and covered by sporangia. Leaves become distorted and wrinkled .wrinkled .

#the whole inflorescence reduced and converted into leafy #the whole inflorescence reduced and converted into leafy bearded structure without bearing any grains.bearded structure without bearing any grains.

Etiology:Etiology:

Causal organism of Downy mildew of Bajra Causal organism of Downy mildew of Bajra

Sclerospora graminicolaSclerospora graminicola

Control:Control:

# Seed Treatment : # Seed Treatment : hot water treatment or treatment with hot water treatment or treatment with Cresan & Agrosan GN.Cresan & Agrosan GN.

# Resistant Varieties .# Resistant Varieties .

# # crop rotation & avoidance of water logging will reduce the crop rotation & avoidance of water logging will reduce the primary inoculums.primary inoculums.

2) Fungal 2) Fungal Wilt.Wilt.

*A wilt disease is any number of disease that affect the *A wilt disease is any number of disease that affect the vascular system of plants. Vascular wilts are widespread, vascular system of plants. Vascular wilts are widespread, very destructive , spectacular and frightening plant very destructive , spectacular and frightening plant disease .disease .

*which characterized by rapid wilting, browning and dying of *which characterized by rapid wilting, browning and dying of leaves and succulent shoots of plant followed by death of leaves and succulent shoots of plant followed by death of the whole plant.the whole plant.

*the infected plant loose turgidity, become flaccid and light *the infected plant loose turgidity, become flaccid and light

green to yellow , droop , finally wiltgreen to yellow , droop , finally wilt brown brown die. die.

*xylem vessel may be clogged with mycelium ,spores or *xylem vessel may be clogged with mycelium ,spores or polysaccharides produced by fungus. Clogging is further polysaccharides produced by fungus. Clogging is further increased by gels and gums formed by accumulation and increased by gels and gums formed by accumulation and oxidation of breakdown products of plant cells attacked by oxidation of breakdown products of plant cells attacked by fungal enzymes.fungal enzymes.

*fungus in leaves cause reduced chlorophyll synthesis along *fungus in leaves cause reduced chlorophyll synthesis along the vein (vein clearing) and reduced photosynthesis, disrupt the vein (vein clearing) and reduced photosynthesis, disrupt the permeability of the leaf cell membranes and their ability the permeability of the leaf cell membranes and their ability to control water loss through transpiration , and thereby to control water loss through transpiration , and thereby result in leaf epinasty ,wilting , interveinal necrosis , result in leaf epinasty ,wilting , interveinal necrosis , browning and finally death.browning and finally death.

Fusarium Wilt Fusarium Wilt ::

*Fusarium wilt is a common vascular wilt fungal disease, *Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to exhibiting symptoms similar to Verticillium wilt . The . The pathogen that causes Fusarium wilt is Fusarium oxysporum .pathogen that causes Fusarium wilt is Fusarium oxysporum .

*F. oxysporum*F. oxysporum is a common soil saprophyte that infects a wide  is a common soil saprophyte that infects a wide host range of plant species around the world. Development of host range of plant species around the world. Development of the disease is favored by high temperatures and warm moist the disease is favored by high temperatures and warm moist soils. soils.

*The fungal pathogen *The fungal pathogen Fusarium oxysporumFusarium oxysporum affects a wide  affects a wide variety of hosts of any age. Tomato, tobacco, legumes, variety of hosts of any age. Tomato, tobacco, legumes, cucurbits, sweet potatoes and banana are a few of the most cucurbits, sweet potatoes and banana are a few of the most susceptible plants, but it will also infect other herbaceous susceptible plants, but it will also infect other herbaceous plants. plants. 

**Fusarium oxysporumFusarium oxysporum generally produces symptoms such as  generally produces symptoms such as wilting, chlorosis, necrosis, premature leaf drop, browning of wilting, chlorosis, necrosis, premature leaf drop, browning of the vascular system, stunting, and damping-off. The most the vascular system, stunting, and damping-off. The most important of these is vascular wilt.  On olderimportant of these is vascular wilt.  On older plants, plants, symptoms are more distinct between the blossoming and symptoms are more distinct between the blossoming and fruit maturation stages.fruit maturation stages.

Fusarium Wilt Of Fusarium Wilt Of Tomato :Tomato :Symptomatology :Symptomatology :

# slight vein clearing on outer leaflets and drooping of leaf # slight vein clearing on outer leaflets and drooping of leaf

petiolespetioles..# leaves Epinasty caused by drooping of Petioles.# leaves Epinasty caused by drooping of Petioles.

# Later the lower leaves wilt, turn yellow and die and the # Later the lower leaves wilt, turn yellow and die and the entire plant may be killed, often before the plant reaches entire plant may be killed, often before the plant reaches maturity. Wilting of leaves , marginal necrosis , brown maturity. Wilting of leaves , marginal necrosis , brown streaks, defoliation.streaks, defoliation.

# yellowing of the foliage, beginning with the lower leaves # yellowing of the foliage, beginning with the lower leaves and working upward. Yellowing often begins on one side and working upward. Yellowing often begins on one side of the vine. Infected leaves later show downward curling, of the vine. Infected leaves later show downward curling, followed by browning and drying.followed by browning and drying.

# In many cases a single shoot wilts before the rest of the # In many cases a single shoot wilts before the rest of the plant shows symptoms or one side of the plant is affected plant shows symptoms or one side of the plant is affected

first .Main stem is cut, dark, chocolate-brown streaks may be first .Main stem is cut, dark, chocolate-brown streaks may be seen running lengthwise through the stem.seen running lengthwise through the stem.

##This discoloration often extends upward for some This discoloration often extends upward for some distance and is especially evident at the point where the distance and is especially evident at the point where the petioles joins the stem. Vascular browning can be seen in petioles joins the stem. Vascular browning can be seen in infected stems and large leaf petioles.infected stems and large leaf petioles.

# root systems are stunted. The degree of stunting depends # root systems are stunted. The degree of stunting depends upon time of root infection and in some cases adventitious upon time of root infection and in some cases adventitious

roots are formed.roots are formed.

Etiology:Etiology:

Fusarium oxysporum f. sp. lycopersiciFusarium oxysporum f. sp. lycopersici

The pathogen is soil borne and persists for many years in The pathogen is soil borne and persists for many years in the soil without a host. Most infections originate from the the soil without a host. Most infections originate from the fungus associated with infected tomato debris. fungus associated with infected tomato debris.

Control Control ::# Use of Resistant Varieties ( Amelia , BHN-444, Carolina # Use of Resistant Varieties ( Amelia , BHN-444, Carolina

gold, Empire, Florida 47, Floralina , Mountain pride , gold, Empire, Florida 47, Floralina , Mountain pride , etc….)etc….)

# Soil sterilization .# Soil sterilization .

# hot water treatment to seeds.# hot water treatment to seeds.

# Solar heating .# Solar heating .

3) Bacterial Blight of Rice :3) Bacterial Blight of Rice :Damage is due to partial or complete blighting of the leaves or Damage is due to partial or complete blighting of the leaves or

due to complete wilting of the affected tillers leading to due to complete wilting of the affected tillers leading to unfilled grains.unfilled grains.

This disease known since 1881 in Japan , become quite severe This disease known since 1881 in Japan , become quite severe in India since 15 years.in India since 15 years.

In leaf blight disease, the spots enlarge in size, rapidly In leaf blight disease, the spots enlarge in size, rapidly necrotic, and through combine of several small spots, may necrotic, and through combine of several small spots, may produce large dead areas of various shapes.produce large dead areas of various shapes.

Bacterium induce either wilting of plant or leaf blight .Wilting Bacterium induce either wilting of plant or leaf blight .Wilting syndrome known as ‘Kresek’ occurs sporadically in the field syndrome known as ‘Kresek’ occurs sporadically in the field causing serious damage.causing serious damage.

Bacterial blight commonly occur within 3-4 weeks after Bacterial blight commonly occur within 3-4 weeks after transplantation of crop. Bacterial blight of rice causes transplantation of crop. Bacterial blight of rice causes

annual losses as high as 60%.annual losses as high as 60%.

Symptomatology :Symptomatology :# Linear yellow to straw colored stripes with wavy margin # Linear yellow to straw colored stripes with wavy margin

developed usually on both the edges of the leaf. The developed usually on both the edges of the leaf. The stripes usually develop from the tip towards the base stripes usually develop from the tip towards the base dry rapidly dry rapidly wither. wither.

# Spots formed on leaf sheath combine to form straw brown # Spots formed on leaf sheath combine to form straw brown

large lesions.large lesions. # Bacterial ooze, pale amber in color, is found on the affected # Bacterial ooze, pale amber in color, is found on the affected

portions. On drying, these drops make crust and make the portions. On drying, these drops make crust and make the leaf surface rough.leaf surface rough.

# As disease advances, the lesions cover the entire blade, # As disease advances, the lesions cover the entire blade, turn white & later become grayish due to the growth of turn white & later become grayish due to the growth of saprophytic fungi.saprophytic fungi.

# wilt affected tillers leading to unfilled grains.# wilt affected tillers leading to unfilled grains.

Etiology:Etiology:

Xanthomonas campestris Xanthomonas campestris pathovarpathovar oryzae oryzaeGram –ve rod , 0.5 – 1.0 micron ,non – sporing with a single Gram –ve rod , 0.5 – 1.0 micron ,non – sporing with a single

polar flagella, aerobic and TDP – 53 degree Celsius .polar flagella, aerobic and TDP – 53 degree Celsius .

On N.A , colonies are tiny , circular & bright yellow.On N.A , colonies are tiny , circular & bright yellow.

The pathogen may survive on crop debris in soil. The The pathogen may survive on crop debris in soil. The bacterium is carried over through infected seeds.bacterium is carried over through infected seeds.

Rainy weather , strong wind and temperature of 22-26 C Rainy weather , strong wind and temperature of 22-26 C favor the rapid spread of disease in the field.favor the rapid spread of disease in the field.