The document provides a detailed overview of major rice crop diseases, including their causal organisms, symptoms, infection cycles, and management practices. Key diseases discussed include rice blast, brown spot, bacterial blight, sheath blight, false smut, khaira disease, and tungro disease, highlighting their etiology and prevention methods. Recommended management strategies encompass cultural practices, the use of resistant varieties, and chemical treatments tailored to each disease.

1. Name - Dhore Sayali Sharad
Reg. No – AKN-2017/020
Semester – V
Submitted To –
Prof.S.K.Sonawane
K.K. Wagh College of Agriculture, Nashik

2. Topic : Diseases Of Rice
Crop
Course Title – Diseases of field and horticultural
Crops And Their Management(Part -1)
Course no – PATH-354

3. Major Diseases of Rice & their Causal
Organism:
Name of Disease Causal Organism
• Rice Blast Pyriculria grisea
• Brown Spot of Rice Helminthosporium oryzae
• Bacterial Blight Xanthomonas oryzae pv. oryzae
• Sheath Blight of Rice Rhizoctonia solani
• False Smut Ustilaginoidea virens
• Khaira Disease Zinc (Zn) Deficiency
• Tungro Disease of Rice Rice tungro virus

4. 1. Rice Blast:
CO.- Pyriculria grisea
Infected leaf
• Disease can infect paddy at all growth stages
and all aerial parts of plant (Leaf, neck and
node).
• Among the three leaves and neck infections
are more severe.
• Small specks originate on leaves -
subsequently enlarge into spindle shaped
spots(0.5 to 1.5cm length, 0.3 to 0.5cm
width) with ashy center.
• Several spots coalesce and form big irregular
patches
Symptoms:

5. Leaf Blast :
•Severe cases of infection - entire crop give a
blasted or burnt appearance- hence the name
"BLAST"
•Severe cases - lodging of crop (after ear
emergence)
Neck Blast
•Neck region of panicle develops a black color
and shrivels completely / partially grain set
inhibited, panicle breaks at the neck and hangs
Nodal Blast:
• Nodes become black and break up.
Leaf Collar
Neck Nodal

6. Etiology:
• Mycelium: Septate, hyaline to olivaceous.
• Reproduction is Asexual by curved to fusiform 4 celled hyaline ascospores
produced in perithecia.
Infection:
• PSI: Conidia from infected seeds and plant debries.
• SSI: Air borne conidia.

7. Epidemiology:
• The most favorable conditions for sporulation, spore germination and
infection of plant tissue by the blast fungusinclude high relative humidity,
free moisture on the plant tissue surface and temperatures around 82o F.
• Temperatures cooler or warmer than this slow down disease development
but do not prohibitit.
• As the season progresses, watch out for mild temperatures, calm mornings
and foggy orovercast skies that favor extended free moisture periods, all
conditions that promote blast development.

8. Life Cycle Of Fungi:
 Rice blast fungus starts its infection cycle when a
three-celled conidium lands on the rice leaf surface.
 The spore attaches to the hydrophobic cuticle and
germinates, producing a narrow germ tube, which
subsequently flattens and hooks at its tip before
differentiating into an appressorium.
 The single-celled appressorium matures and the
three-celled conidium collapses and dies in a
programmed process that requires autophagy.
 The appressorium becomes melanized and develops
substantial turgor.
 This translates into physical force and a narrow penetration peg forms at the base, puncturing
the cuticle and allowing entry into the rice epidermis.
 Cell-to-cell movement can initially occur by plasmodesmata.
 Disease lesions occur between 72 and 96 hours after infection and sporulation occurs under
humid conditions; aerial conidiophores with sympodially arrayed spores are carried to new
host plants by dewdrop splash.

9. Management:
Cultural method:
•Remove collateral weed hosts from bunds and channels.
•Use only disease free seedlings.
•Avoid excess nitrogen.
•Apply N in three split doses (50% basal, 25% in tillering phase and 25% N in panicle
initiation stage).
•Use resistant variety CO 47.

10. •Chemical Method:
•Spray after observing initial infection of the disease,
•Carbendazim 50WP @ 500g/ha (or)
•Tricyclozole 75 WP @ 500g/ha (or)
•Metominostrobin 20 SC @ 500ml/ha (or) 47
•Azoxystrobin 25 SC @ 500 ml/ha

11. 2. Brown Spot Of Rice:
CO.- Helminthosporium oryzae
Symptoms:
•Occur in nursery as well as main field.
•Causes blight of seedlings.
•Leaf spotting is very common.
•Isolated brown, round to oval (resemble sesame
seed).
•Spots measures 0.5 to 2.0mm in breadth - coalesce
to form large patches.
Infected leaf

12. •Seed also infected (black or brown spots on glumes spots are covered by
olivaceous velvety growth).
•Infection also occurs on panicle neck with brown colour appearance.
•50% yield reduction in severe cases.
Dark Brown or Black Spots
on Panicle
Glumes and Grains
Brown Spot on Grains

13. Etiology:
Infection:
• PSI: Infected seeds.
• SSI: Collateral hosts.
• Mycelium is inter or intracellular.
• Septate conidiophores emerge in groups through the epidermis or stomata.
• Bears conidia singly, are 8-10 celled, tapering towards end and bludge at middle, brownish in colour.

14. Epidemiology:
• The disease is prevalent throughout the rice growing tracts of the world.
• It is found to be pendemic in heavy rainfall areas viz. the Himalayas, Assam,
Malabar coast and West Bengal.
• The disease is generally severe in soils of low pH, low available potassium
(K2O) and also deficient in essential and trace elements.
• Temperature of 25-30°C
• Relative humidity (>90%)
• Heavy and late north-east monsoon
• Cloudy days
• High doses of N

15. Conidia of Helminthosporium oryzae
Life Cycle of Helminthosporium oryzae

16. Management:
Preventive measures:
•Use of resistant varieties – Rasi, IR 36, Jagannath.
•Proper crop nutrition
•Avoid water stress
•Clean cultivation
Cultural practices:
•Use disease free seeds for sowing.
•Do not use high nitrogenous fertilizer
•Use resistant variety Amruth
Chemical control:
•If the disease observed in the field than spray 1g of ediphenphos or 2g mancozeb
or 2.25g Zineb in 1liter of water

17. 3. Bacterial Blight:
CO.- Xanthomonas oryzae pv. oryzae
Symptoms:
Infected leaf
Kresek Phase:
1) Results from early systemic infection.
2) Leaf rolling, drooping, yellowing and withering of tillers.
3) Death of the affected tillers.
Margin Blight:
1) Watersoaked transluscent spots on margin and along with
midrib.
2) Elongated streaks with wavy margin becoming white yellow
coloured.
3) Streaks coalesce filling vascular bundles with bacteria.
4) Milky exudations from leaf.
5) Grain discolouration with watersoaked spots.

18. Etiology:
Infection:
• PSI: Seed born inoculum carried externally or internally.
• SSI:Wind or water carried inoculum causing passive infection through
stomata, hydathodes or wounds.
• Shape: Rod shaped occureing singly or in pairs.
• Flagellation: Monotrichous, Polar.
• Bacterium is Gram –ve.
• Aerobic and Capsule former.
• No formation of spores.

19. Xanthomonas oryzae
Life Cycle of Xanthomonas oryzae
Fig 1 . Disease cycle of bacterial blight of rice caused by
Xanthomonas oryzae pv. oryzae. Reprinted from [ 67 ]
with permission from APS Press.

20. Management:
Cultural measures:
•Use of resistant varieties - Ajaya, Asha, Biraj, CO-43, Gobind, IR-64, Janaki, PR-4141, Radha, Sona
Mahsuri, Sujata, Suraj, Swarna, Udaya.
•Balanced fertilizer application - Split application of N
•Reduce the disease spread by careful handling of seedlings during transplanting, maintaining
shallow water in nurseries, providing good drainage during severe flooding.
•Reduce the amount of inoculum through clean cultivation and drying the fallow fields.
• Remove collateral weed hosts from bunds and channels.
• Use only disease free seedlings.
• Apply N in three split doses, 50% basal, 25% in tillering phase and 25%N in panicle initiation
stage.

21. Chemical control:
• Seed treatment with 0.1 g Streptocycline and 0.1 g Copper Sulfate
or 0.3 g Agrimycin-100 and 0.1 g Copper Oxychloride in one liter
of water for 20 minutes.
• Foliar spray of 0.05 g Streptocycline and 0.05 g Copper Sulfate.

22. 4.Sheath Blight of Rice:
CO.- Rhizoctonia solani
Symptoms:
•Plants affected exhibit stunting and reduced tillering. Their
leaves become yellow or orange-yellow, may also have rust-
colored spots.
•Discoloration begins from leaf tip and extends down to the
blade or the lower leaf portion.
•Delayed flowering, - panicles small and not completely
exerted.
•Most panicles sterile or partially filled grains.
Infected sheath
Infected leaves

23. Etiology:
Infection:
• PSI: Seed and soil born inoculum.
• SSI:Sclerotial bodies left in the field from previous crop and weeds,
Mycelium in the plant debris.
•The fungus produces usually long cells of septate mycelium which are hyaline when young,
yellowish brown when old.
•It produces large number of globoses sclerotia, which are initially white, later turn to brown
or purplish brown.
•Sclerotia consist of compact masses of mycelia. They are irregular, hemispherical, flattened
at the bottom, white when young, and turn brown or dark brown when older. Individual
sclerotia are 1-6 mm in diameter. They may unite to form a larger mass. Large sclerotia are
significantly more virulent than smaller ones.

24. Epidemiology:
•Presence of sclerotia or infection bodies floating
on the water.
•Presence of the disease in the soil.
•Relative humidity from 96 to 100%.
•Temperature from 28-32 °C.
•High levels of nitrogen fertilizer.
•High seeding rate or closing plant spacing.
•Frequent rain.

25. Life Cycle of Rhizoctonia solani

26. Management:
Cultural Practices:
•Moderately Resistant Varieties: Swarnadhan, Vikramarya, Radha, Pankaj,
Manasarovar, Mandya Vijaya.
•Avoid using infected seed.
•Apply moderate 'N' levels (80-100 kg/ha) in 3-4 splits.
•Avoid excess 'N', skip final 'N' in sheath blight infected fields.
•Destroy stubbles / weeds, etc.
•Check brown plant hopper population.

27. Chemical control:
•1g of carbendazim 50 WP(540g/acre) or 2g mancozeb 75 WP in 1 liter of
water.
•Seed treatment with carendizm 2.0g/kg of seeds.
•Spraying fungicides of 1g carbendazim 50WP (540g/acre) or 2.0g mancozeb
75WP OR 1ml hexaconozole in 1 liter of water.

28. 5.False Smut Of Rice:
CO.- Ustilaginoidea virens
Symptoms:
•Only few grains in a panicle are usually infected
and the rest are normal.
•Individual rice grain transformed into a mass of
yellow fruiting bodies.
•Growth of velvety spores that enclose floral parts.
•Immature spores slightly flattened, smooth, yellow,
and covered by a membrane.
•Growth of spores result to broken membrane.
•Mature spores orange and turn yellowish green or
greenish black.
Infected panicle
Infected grain

29. Etiology:
Infection:
• PSI: Seed born inoculum.
• SSI:Plant debries,Many grasses and Wild rice.
• Vegetative mycelium: Septate
• Asexual reproduction: By conidia
• Sexual reproduction: By ascospores, which are produced in peripheral perithecia of stroma.
• The stroma are produced as result of germination of sclerotia.

30. Epidemiology:
•Low temperature (20°C).
•High relative humidity (>92%).
•Moderate rainfall with intermittent clear and drizzling weather
during flowering.
•More prevalent in seasons favorable for good growth and high yields.

31. Management:
Cultural Control:
•Use disease free seeds for sowing.
•Hot water treatment of seeds at 52°C for 10 min.
•Removal and destruction of diseased panicles in field.
•Seed treatment with carbendazim 2.0g/kg of seeds.
•Remove alternative hosts, including grassy weeds, especially Common barnyardgrass
(Echinochloa crus-galli) and Jungle rice (Echinochloa colona).
Chemical Control:
• Two sprayings of Propiconazole 25 EC @ 500ml/ha (or) Copper hydroxide 77 WP @
1.25 kg/ha at boot leaf and 50% flowering stages.

32. 6.Khaira Disease:
Caused Due to- Zinc (Zn) Deficiency
Symptoms:
•Dusty brown spots on upper leaves of stunted plants.
•Uneven plant growth and patches of poorly established hills in the field, but
the crop may recover without intervention.
•Increased spikelet sterility in rice.
•Chlorotic midribs, particularly near the leaf base of younger leaves.
•Leaves lose turgor and turn brown as brown blotches and streaks appear on
lower leaves, enlarge, and coalesce.
•White line sometimes appears along the leaf midrib.
•Leaf blade size is reduced.
Infected leaves

33. Management:
•Grow Zn-efficient varieties.
•Use fertilizers that generate acidity (e.g., replace some urea with ammonium sulfate).
•Apply organic manure before seeding or transplanting or applied to the nursery seedbed a few
days before transplanting.
•Allow permanently flooded fields (e.g., where three crops per year are grown) to drain and dry out
periodically.
•Monitor irrigation water quality.
•Broadcast ZnSO4 in nursery seedbed.
•Dip seedlings or presoak seeds in a 2−4% ZnO suspension .

34. 7.Tungro Disease of Rice:
CO.- Rice tungro virus
Symptoms:
•Plants affected by tungro exhibit stunting and reduced tillering. Their
leaves become yellow or orange-yellow, may also have rust-colored
spots.
•Discoloration begins from leaf tip and extends down to the blade or the
lower leaf portion.
•Delayed flowering, panicles small and not completely exerted.
•Most panicles sterile or partially filled grains.
•Tungro virus disease affects all growth stages of the rice plant
specifically the vegetative stage.
Yellowing from
Tip to Downwards
Tungro affected field

35.  Transmission:
• Tungro virus disease is transmitted by leafhoppers, wherein the most efficient vector is the
green leafhopper, Nephotettix virescens.
• No latent period in vector.
• Retention of infectivity for 6 days after acquisition.
Epidemiology:
•Presence of the virus sources.
•Presence of the vector.
•Age and susceptibility of host plants.
•Synchronization of the three above factors.
•All growth stages of the rice plant specifically the vegetative stage.

36. Etiology:
Composite disease caused by association of two unrelated viruses:
A) RTBV:
i. Bacilliform
ii. Double stranded DNA
iii. Coat Protein of 36k- MW
iv. Responsible for induction of majority of symptoms.
A) RTSV:
i. Isomeric
ii. Single stranded RNA
iii. Essential for vector transmission i.e. No vector transmission of RTBV in the absence of R

37. Management:
Cultural methods:
•Planting of resistant varieties against tungro virus disease is the most economical
means of managing the disease.
•Use Resistant varieties like IR 36, IR 50 ,ADT 37, Ponmani,Co 45, Co 48,
Surekha, Vikramarya, Bharani, IR 36 and white ponni .
•Among the cultural management practices, adjusting the date of planting is
recommended.
• In epidemic areas follow rotation with pulses or oil seeds.
•Apply neem cake @ 12.5 kg/20 cent nursery as basal dose.
• Plouging and harrowing the field to destroy stubbles right after harvest in order to
eradicate other tungro hosts are also advisable.
•Destruction of weed hosts on bunds.

38. Chemical methods:
• Leaf yellowing can be minimized by spraying 2 % urea mixed with Mancozeb at
2.5 gm/lit.
•Instead of urea foliar fertilizer like multi-K (potassium nitrate) can be sprayed at
1 per cent which impart resistance also because of high potassium content.
•Green leaf hoppers as vectors are to be controlled effectively in time by
spraying.
•In nursery when virus infection is low, apply Carbofuran granules @ 1 kg./ha to control
vector population.
•Spray insecticides twice, 15 and 30 days after transplanting.
Monocrotophos 36 WSC (40 ml/ha)
Fenthion 100 EC

39. Disease Causal organism Biocontrol agent
Blast Pyricularia grisea (Cooke) Sacc. Pseudomonas
fluorescens
Brown spot Bipolaris oryzae (Breda de Haan)
Shoemaker
Pseudomonas sp.
P. aeruginosa
Bacillus sp.
B. subtilis
Bacterial
blight
Xanthomonas oryzae pv.
oryzae
(Ishiyama) Swing et al.
Bacillus sp.
Tungro Rice tungro virus
Vector - Nephotettix spp.
P. fluorescens (for
vector)
Biological Control Of Rice Diseases:

40. Reference:
 www.plantwise.org
 http://agritech.tnau.ac.in
 www. Researchgate.com
 www.agropedia.ac.in
 www.knowledgebank.irri.org
 Practical manual on Diseases of Field Crops and their Management