Diseases of rice

The overall description of major diseases of Rice or Paddy crop is ellustrated in presentation. The students prepairing for Agriculture can feel helpful. Thank You!

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) D eficiency 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 82 o   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: R ice 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. S eptate 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 (K 2 O) 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: Results from early systemic infection. Leaf rolling, drooping, yellowing and withering of tillers. Death of the affected tillers. Margin Blight: Watersoaked transluscent spots on margin and along with midrib. Elongated streaks with wavy margin becoming white yellow coloured. Streaks coalesce filling vascular bundles with bacteria. Milky exudations from leaf. 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) D eficiency 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 ZnSO 4  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: Bacilliform Double stranded DNA Coat Protein of 36k- MW Responsible for induction of majority of symptoms. A) RTSV: Isomeric Single stranded RNA Essential for vector transmission i.e. No vector transmission of RTBV in the absence of RTSV.

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 C rops and their Management