Farmers' Training- Insect Pest and Crop Diseases
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Transcript of Farmers' Training- Insect Pest and Crop Diseases
FARMERS’ TRAININGDiseases and Insect Pests
ARUN KUMARFormer Principal Scientist, CAZRI, Jodhpur, India
Diseases 14.1% Insects 10.2% Weeds 12.2% Total av. looses 36.5%
ESTIMATED ANNUAL LOSSES WORLDWIDE DUE TO DISEASES
Losses are more in developing world and less in developed world
PART I- (A) IMPORTANCE OF PLANT PATHOLOGY
• The disease triangle: plant, pathogen and the environment
Disease
Susceptible Host
Favo
rable
envir
onmen
t
Virulent
Pathogen
HEALTHY AND DISEASED PLANT• A plant is considered healthy if it
functions to the best of its genetic ability
• When a plant function is interfered by a microorganism or environmental factor the plant becomes diseased
• The visible changes are expressed in the form of symptoms or signs in a diseased plant
SYMPTOMS OF PLANT DISEASES CAUSED BY FUNGI
Alternaria leaf spot Cercospora leaf spot Powdery mildew
Downy mildew Leaf Blast Ergot Stem rust
SYMPTOMS OF BACTERIAL DISEASES
Citrus canker by Xanthomonas citri Angular leaf spot of cotton
Lima bean spot
NUTRITIONAL DEFICIENCY IN PLANTS
Iron deficiency in maize Zinc deficiency in tomato
Types of malformations with a healthy ear head (extreme left)
Infected plant showing asexual sporulation as half-leaf symptom.
DOWNY MILDEW DISEASE OF PEARL MILLET
SPHACELOTHECA- COVERED KERNEL SMUT
Teliospores of S. sorghi are seed-borne and germinate within the seed.
Seedling plants are infected, but symptoms generally are not apparent until heading.
Smutted ovaries are covered by a thick membrane
Seedling infection by sporidia produced by teleutospores present on seed or in the soil
USTILAGO-THE SMUTS Plant is systemically
infected, looks normal till ears appear
Seeds covered with thin layer, which ruptures to disperse black sooty mass of teleutospores
In case of corn the fungus forms galls on all above-ground parts
wheat
Corn
ALTERNARIA LEAF SPOT Most characteristic symptom is brown or dark spots
on older leaves. The circular to angular spots enlarge and soon
develop dark, concentric rings or ridges, giving a target-like appearance.
Spotted leaves soon turn yellow, wither, and drop. Leaf spots are usually covered with dark, velvety
spores (conidia).
Guar
Sesame
DISEASE CAUSING AGENTS
Non Infectious diseases
• Diseases caused by low or high temperature
• Diseases caused by lack or excess soil water
• Diseases caused by lack or excess light• Diseases caused by lack of oxygen• Diseases caused by air pollution• Diseases caused by nutrient deficiencies• Diseases caused by mineral toxicities
Bacterial Diseases
• Bacterial galls: In some cases, toxic materials are produced that cause plant tissues of roots, stems or leaves to grow abnormally as in crown gall.
• Bacterial leaf spot disease: The bacteria usually enter through leaf stomata.
• Symptoms include water-soaking, slimy texture, fishy or rotten odor, confined initially between leaf veins resulting in discrete spots that have straight sides and appear angular.
Disease Development• Infections occur through leaf scars and wounds. These
give rise to small cankers in which the bacteria survive the winter.
• Rain or water splash, and pruning tools spread the bacterium.
• Bacteria overwinter in active cankers, in infected buds, and on the surface of infected and healthy trees and weeds.
• The bacterium reproduces best between 21ºC and 25ºC.
• Generally disease seems to be more severe after cold winters and prolonged spring rains.
Viruses
• Viruses are "submicroscopic" entities that infect individual host plant cells.
• Viruses are obligate parasites: They can only replicate themselves within a host's cell.
• In the virus infected plant, production of chlorophyll may cease (chlorosis, necrosis)
• Cells may either grow and divide rapidly or may grow very slowly and be unable to divide
Viral Diseases• > 400 viruses infect plants; few are
economically important pathogens• The infection remains forever• Viruses are transmitted from plant to
plant by living factors: insects, mites, fungi and nematodes
• Or non-living factors: rubbing, abrasion or other mechanical means (including grafting or other forms of vegetative propagation)
• Occasionally transmitted in seed.
Virus Disease SymptomsFour types of major
symptoms :1. Lack of chlorophyll formation
in normally green organs
2. Stunting or other growth inhibition
3. Distortions
4. Necrotic areas or lesions
Plant Pathology: The Practice
• Some plant disease makes the plant poisonous to humans and animals such as ergot of rye, pearl millet and wheat
• Several fungi will make hay poisonous• May contain nematodes which carry virus• Plant disease causes great financial loss
from a few % to total crop• The cost of disease control must be less
than cost of crop loss
FUNGI AS RESOURCEFUNGI AS RESOURCE Fungi constitute largely
unexploited resource Strains of fungi maintained in
culture collections In over 200 collections number
exceeds 1 lack 70 thousand Around 7 thousand species are
represented
Economic Importance of Fungi
FERMENTED FOODSTUFFS / DRINKSFERMENTED FOODSTUFFS / DRINKS In Asia many
fermented foodstuffs and drinks are based on fungi
This include species of Aspergillus, Monascus, Mucor and Rhizopus
Role of certain Penicillium spp.
(P. camembertii and P. roquefortii) is important in cheese production
BIOTECHNOLOGICAL APPLICATIONSBIOTECHNOLOGICAL APPLICATIONS
FOOD FOR MANFOOD FOR MAN Mushrooms grown in pastures and
forests of different geographical regions
No. of species are more than 500 Around 20 spp. are currently
exploited commercially (Agaricus, Lentinula, Tricholoma, Volvariella, Pleurotus etc. )
EDIBLE MUSHROOMS
Podaxis pistillaris
Phellorinia inquinansMorchella sp.
Pleurotus sajor-caju
ANTIBIOTIC INDUSTRYANTIBIOTIC INDUSTRY
Antibiotic is a chemical, effective at very low concentration, produced by or derived from certain fungi, bacteria, and other organisms, that can destroy or inhibit the growth of other micro-organisms. Antibiotics are widely used in the prevention and treatment of infectious diseases.
INDUSTRIAL CHEMICALSCHEMICAL
Aspergillus niger Citric and gluconic acid
Eremothecium ashbyii Vitamins - riboflavin Aureobasidium pullulans
Polysaccharides- pullulan
Rhizomucor pusillusPenicillium roquefortiiAspergillus oryzae
Enzymes - Rennin LipaseProtease
Trichoderma viride Cellulase
FUNGUS
a). Beauveria bassiana produces creamish-white conidia alternately on an extending tip of a conidiophore
b). Metarhizium anisopliae produces greenish- conidia in chains from phialides
Beauveria bassiana
Metarhizium anisopliae
Sporulation of Beauveria on green cockchafer beetle
Metarhizium spores on locust
Beauveria bassiana on leaf hopper h
Metarhizium anisopliae on bug and beetle beetles
INSECT BIOCONTROLINSECT BIOCONTROL
BIOCONTROL OF PLANT DISEASESBIOCONTROL OF PLANT DISEASES
FUNGUS PLANT DISEASETrichoderma harzianum
Leaf blights, wilts, root rot
T. koningii T. pseudokoningii
Foot rot, Collar rotRoot and Butt rot in tree
T. viride Die-back or anthracnose, LCD of Chilli
Gliocladium virens Downy Mildew of pearl millet
Trichoderma Colonizing Fungal Mycelium
BIOFERTILIZER FOR FORESTRY AND ORCHID INDUSTRYBIOFERTILIZER FOR FORESTRY AND ORCHID INDUSTRY
Sclerocystis microcarpa Gigaspora margaritaGlomus macrocarpum
VESICULAR ARBUSCULAR MYCORRHIZA (VAM Fungi)150 species in Zygomycotina
Obligate symbiotic association with agricultural,medicinal,shrubs and treesImprove plant growth and nutrient uptake(phosphorus), reduce water stressProduce growth promoters and induce resistance to plants against pathogens
Role in organic farming and hardening in plant tissue culture
ECONOMICALLY IMPORTANT PHYTOPATHOGENIC BACTERIA
Bacterial wilt of egg plant Bacterial canker & gumming in Prunus sp.
R
S
R
R
Exposed cambium necrotic, discolored area
USEFUL BACTERIAL PATHOGENSTaxon Function
Agrobacterium radiobacter
Biological control, Biodegradation of Atrazine
A. tumefaciens Plasmid vector for plant transformation
Erwinia amylovora Source of harpin, an elicitor of disease resistance in plants
Xanthomonas campestris pv. Campestris
Xanthan gum, a polysaccharide used in food production, agriculture, cosmetics and pharmaceuticals.
Several plant associated bacteria
Restriction endonucleases, enzymes used for specific cutting of DNA in scientific research
PLANT PATHOGENSPLANT PATHOGENS
VIRUSESVIRUSES
TULIPOTULIPOMANIAMANIA
SYMPTOMS OF VIRAL DISEASES
MAJOR DISEASE SYMPTOMS ARE
• Leaf yellowing (either of the whole leaf or in a pattern of stripes or blotches)
• Leaf distortion (e.g. curling) and/or
• Other growth distortions (e.g. stunting of the whole plant, abnormalities in flower or fruit formation)
LEAF CURL OF CHILLI (LCD)
Disease is caused by Begomovirus (ChiLCuV)
The disease is transmitted by insect vectors such as
whitefly and thrips
• Curling of upper leaves with shortened internodes
• Severely infected plants produce clusters of reduced sized leaves with fewer flowers and fruits
• Small sized fruits are produced with deformed seeds Small sized fruits
GOLDEN YELLOW BEAN MOSAIC OF MOTHBEAN (Vigna aconitifolia )
There are two types of infections: localized and systemic. In localized infections (as shown here), the upper leaves are affected; in systemic infections, the
whole plant becomes chlorotic and stunted. The virus is transmitted by whiteflies
3. Transmission Through Vectors
(i). Insects: Some insect species are the vector of plant viruses which can carry/ transmit viruses from infected plants to the healthy plants e.g.
• aphid (potato virus Y) • white flies (tobacco/chilli leaf curl) • beetles (cowpea mosaic virus) • mealy bugs (cacao mottle leaf) • thrips (tomato spotted wilt) • lace bugs (sugar beet viruses) • mites (sterility mosaic of arhar)• leaf hoppers (beet curly top, rice tungro) • plant-hoppers (maize mosaic)• tree hopper (tomato pseudo curly top)
(ii) NematodesFive genera of nematodes viz., Xiphinema, Longidorus, Paralongidorus, Trichodorus and Paratrichodorus can transmit plant viruses (iii) Fungi Some species of fungi can also transmit viruses e.g. Olpiduim brassicae (tobacco necrosis), O. cucurbitacearum (cucumber necrosis), Polymyxa graminis (oat mosaic, wheat mosaic), P. betae (beet necrotic yellow vein) and Spongospora subterranea (potato mop top) etc.
4. Dodder transmission
Many viruses can be transmitted through dodder (Cuscuta spp.). Dodder transmission is used in the laboratory to transfer viruses from the hosts
5. Transmission through seeds and pollens
Seed coat (testa), embryo, and also pollens of some plants can transmit viruses. e.g. alfalfa mosaic, barley stripe mosaic, bean common mosaic and lettuce mosaic are transmitted by both seeds and pollens of Medicago sativa, Hordeum vulgare, Phaseolus vulgaris and Lactuca sativa, respectively.
• The multicolor effects of intricate lines and flame-like streaks on the petals were vivid and spectacular and made them even more exotic-looking, highly sought-after plants
• Tulip breaking virus is a member of the potato virus Y group
Variegated tulips was a complete mystery till 1927 when it was known that this is due to the infection of a VIRUS (Tulip break virus, Tulip mosaic virus or TBV )
PLANT PATHOGENSPLANT PATHOGENS MYCOPLASMA (MLO)MYCOPLASMA (MLO)
SUBJECT EXPERTDr. ARUN KUMARDr. ARUN KUMAR
PART-IVPART-IV
• Several hundred important food, vegetable, and fruit crops; ornamental plants; and timber and shade trees are affected
• Aster yellows phytoplasma causes major economic losses of vegetable crops (lettuce, carrot, and celery), ornamental plants (gladiolus, hydrangea, China aster, and purple coneflower)
• Peanut and Sweet potato witches’ broom, sesame and soybean phyllody cause considerable losses of these crops in Asia
MYCOPLASMA DISEASES
• Proliferation of axillary buds/shoots changing in “witches’ broom” symptoms
• Sterility of flowers• Abnormal internode elongation• Generalized stunting with yellowing or
reddening of leaves, decline and death of plant• Phytoplasmas are transmitted by insects
belonging to the families- Cicadellidae, Cixidae, Psyllidae, Delphacidae and Derbidae
SYMPTOMS AND TRANSMISSIONProfound disturbance in the normal balance of growth
regulators, leading to virescence or phyllody (green leaf-like structures instead of flowers) results in:
Empoasca fabae
INSECT VECTORS OF MLOs
Nephotettix cincticeps
SESAMUM PHYLLODY
2nd & 4th from left healthy
Sesamum Phyllody in severity
Little leaf disease of Eggplant or BrinjalFirst reported from India by Thomas and Krishnaswami in 1939
MYCOPLASMA LIKE ORGANISMS
Electron micrographs of cross sections of sieve tubes showing variations in the size and shape of
phytoplasmas infecting plants
PLANT PATHOGENSPLANT PATHOGENS Phanerogamic Parasites
SUBJECT EXPERTDr. ARUN KUMARDr. ARUN KUMAR
PART- IVPART- IV
LORANTHUS
It is non chlorophyllous, leaf less parasitic seed plant
It is yellow, pink or orange in colour and attached to the host
They do not bear leaves but have minute functionless scale leaves
CUSCUTA or DODDER (Amarbel)
CUSCUTA / DODDER
CUCUTA FLOWERS
FRUITS OF CUSCUTA
SEVERE INFESTATION OF DODDER
OROBANCHE
Lauki-Mula
Striga hermonthica parasitising sorghum crop
THANKS