Rice diseases and their management
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Rice diseases and their management
- 1. RICE DISEASES AND THEIR MANAGEMENT ANDRELORD G. MEDINA AGRICULTURIST I-REGULATORY DIVISION
- 2. What is Plant Disease? Plant Disease - Any abnormalities, disturbances, malfunctions in plant’s life that may affect the normal physiological processes that can give economic losses.
- 3. Diseases cause substantial losses in rice production. Published data on actual losses vary with region, disease severity, and varietal susceptibility.
- 5. BACTERIAL PATHOGENS BACTERIAL LEAF BLIGHT (BLB) Causal organism: Xanthomonas oryzae pv. oryzae (Xoo) SYMPTOMS: • Wilting of seedlings (kresek) • Appearance of bacterial ooze that looks like a milky or opaque dewdrop on young lesions early in the morning • Drying/yellowing of leaf tips and margins Source: RCPC-1 Source: IRRI
- 7. BACTERIAL PATHOGENS BACTERIAL LEAF STREAK(BLS) Causal organism: Xanthomonas oryzae pv. oryzicola SYMPTOMS: • narrow, dark-greenish, water-soaked, interveinal streaks of various lengths, in leaf blades. -Chin Khoon Min • Lesions begin as small, interveinal, water-soaked (dark green) streaks which later become translucent.. -T.W. Mew/IRRI • severe damage; the translucent streaks enlarge and coalesce turning light brown then greyish-white until the whole leaf dries up. -T.W. Mew/IRRI Source: RCPC-1Source: RCPC-1Source: IRRI
- 8. BACTERIAL PATHOGENS MANAGEMENT: • Plant resistant varieties • Use balanced amounts of plant nutrients, especially nitrogen. • Ensure good drainage of fields • Sanitation - Keep fields clean. • Dry Fallowing • Solarization • Use of chemicals (thiodiazole-copper; Cuprous Oxide) as last resort
- 9. FUNGAL PATHOGENS RICE BLAST Causal organism: Magnaporthe oryzae SYMPTOMS: • white to gray-green lesions or spots, with dark green borders. • Older lesions on the leaves are elliptical or spindle- shaped and whitish to gray centers with red to brownish or necrotic border. • Some resemble diamond shape, wide in the center and pointed toward either ends. • Lesions can enlarge and coalesce, growing together, to kill the entire leaves.
- 10. Source: RCPC-1
- 17. Neckblastphotos:Castilla,N.P.2004.IRRI ExperimentStation;Castilla,N.P.2004. Sichuanprovince,China. •When a grayish brown lesion around the neck is exhibited, the panicles fall during severe infection. Brown lesions on the panicle branches and spikelets are also produced (neck blast) Panicle blast photos: Castilla, N. P. 2004. IRRI Experiment Station; Castilla, N. P. 2006. Lampung province, Indonesia. •Dark, necrotic lesions cover partially or completely the panicle base, or the uppermost internode, or the lower panicle axis. Panicles are grayish and have either partially filled or unfilled grains (panicle blast)
- 19. FUNGAL PATHOGENS MANAGEMENT: • Plant resistant varieties • Use balanced amounts of plant nutrients, especially nitrogen. • Adjust planting time. Sow seeds early, when possible, after the onset of the rainy season. • Flooding • Silicon fertilizer application • Use of chemicals (edifenphos, benomyl, triazoles and strobilurins) as last resort
- 20. FUNGAL PATHOGENS SHEATHBLIGHT Causal organism: Rhizoctonia solani SYMPTOMS: • oval or ellipsoidal greenish gray lesions, usually 1-3 cm long, on the leaf sheath and leaf • lesions on the leaves usually have irregular lesions, often with gray-white center and brown margins as they grow older. • in subtropical environments, the disease is mostly initiated by sclerotia (up to two million of which can be produced per square meter in a diseased crop).
- 21. Source: AgFax
- 22. Source: IRRI
- 23. on leaf sheath: oval gray spots that later enlarge; with black brown margins and gray center •on leaves: lesions are irregular, banded with green brown coloration; center is grayish white; leaf whitens; panicle exertion affected when flag leaf is infected. Photo by Peggy Greb
- 24. FUNGAL PATHOGENS MANAGEMENT: • Proper fertilization • Proper crop density,canopy structure, & spacing • Sanitation • Deep plowing • Solarization • drain rice fields relatively early in the cropping season to reduce sheath blight epidemics. • use fungicide (difenoconazole, iprodine, benomyl)
- 25. FUNGAL PATHOGENS BROWN SPOT Causal organism: Cochliobolus miyabeanus SYMPTOMS: • small, circular, and dark brown to purple-brown. Fully developed lesions are circular to oval with a light brown to gray center • On susceptible varieties, lesions are 5−14 mm long which can cause leaves to wilt. On resistant varieties, the lesions are brown and pinhead-sized
- 26. FUNGAL PATHOGENS MANAGEMENT: • Use resistant varieties • Proper fertilization • Use fungicides (e.g., iprodione, propiconazole, azoxystrobin, trifloxystrobin, and carbendazim) as seed treatments. • Treat seeds with hot water (53−54°C) for 10−12 minutes before planting, to control primary infection at the seedling stage. To increase effectivity of treatment, pre-soak seeds in cold water for 8 hours.
- 27. FUNGAL PATHOGENS SHEATHROT Causal organism: Sarocladium oryzae MANAGEMENT: • use healthy seeds • Underplowing or burning of straw and stubble • Optimum plant spacing (20x30cm) • Proper fertilization • Use of chemicals (carbendazim, edifenphos, mancozeb, benomyl and copper oxychloride)
- 28. FUNGAL PATHOGENS STEMROT Causal organism: Sclerotium oryzae MANAGEMENT: • use of resistant cultivars • Underplowing or burning of straw and stubble • Proper fertilization • Use of chemicals (fentin hydroxide, thiophanate-methyl, Ferimzone and validamycin A)
- 29. FUNGAL PATHOGENS NARROW BROWN SPOT Causal organism: Cercospora janseana MANAGEMENT: • Use resistant varieties. • Keep fields clean. Remove weeds and weedy rice in the field and nearby areas to prevent the disease to occur across cropping seasons. • Proper fertilization • Use of chemicals (propiconazole, azoxystrobin)
- 30. FUNGAL PATHOGENS LEAF SCALD Causal organism: Microdochium oryzae MANAGEMENT: • Proper fertilization • Chemicals such as benomyl, carbendazim, quitozene, and thiophanate-methyl can be used to treat the seeds to eliminate the disease. In the field, spraying of benomyl, fentin acetate, edifenphos, and validamycin significantly reduce the incidence of leaf scald. Foliar application of captafol, mancozeb, and copper oxychloride also reduces the incidence and severity of the fungal disease.
- 31. FUNGAL PATHOGENS BAKANAE Causal organism: Gibberella fujikoroi MANAGEMENT: • Use clean seeds • Use salt water to separate lightweight, infected seeds during soaking • Use fungicides as seed treatments (benomyl, triflumizole, propiconazole, prochloraz or a combination of thiram + benomyl) Source: RCPC-1
- 32. FUNGAL PATHOGENS FALSESMUT Causal organism: Ustilaginoidea virens (Cooke) Takah. MANAGEMENT: • Sanitation • Remove infected seeds, panicles, and plant debris after harvest. • Reduce humidity levels through alternate wetting and drying (AWD) rather than permanently flooding the fields. • Use moderate rates of nitrogen. • Use certified seeds. Resistant varieties have been reported. • Treat seeds at 52°C for 10 min.
- 33. VIRAL PATHOGENS TUNGRO DISEASE Causal organism: Rice Tungro Virus (RTV) SYMPTOMS: • Yellow or orange-yellow discoloration. • mottling or striped appearance, rust-colored spots, and inter-veinal necrosis. • stunting, delayed flowering, reduced number of tillers, small and not completely exerted panicles, partially filled grains, covered with dark brown blotches. • Presence of Green Leaf Hoppers (GLH) • Yellow patches eventually turning into hopperburn
- 34. VIRAL PATHOGENS MANAGEMENT: • Grow tungro or leafhopper resistant varieties • Practice synchronous planting with surrounding crops and farms • Plow infected stubbles immediately after harvest to reduce inoculum sources, and destroys the eggs and breeding sites of green leaf hopper • If infected, control hoppers with insecticides and pull out RTV-infected plants • Once a rice plant is infected by tungro, it cannot be cured.
- 35. VIRAL PATHOGENS RICE RAGGEDSTUNT DISEASE Causal organism: Rice Ragged Stunt Virus (RRSV) MANAGEMENT: • There are no specific control measures for the ragged virus disease except for the use of resistant varieties. Because some rice varieties are resistant to the brown planthopper, to the virus, and to both. • Cultivars resistant to the vector have low disease incidence.The application of insecticides to migratory planthoppers is being used in temperate countries to reduce disease incidence.
- 36. Rice Ragged Stunt Virus Disease
- 37. VIRAL PATHOGENS RICE GRASSYSTUNT DISEASE Causal organism: Rice Grassy Stunt Virus (RGSV) MANAGEMENT: • Plant variety with BPH resistance. • Plow under infected plants and stubbles. • Do not apply excess N-fertilizer. • Monitor field and note increase in planthopper population
- 42. Illustrated guide to disease symptoms on leaves BACTERIAL LEAF BLIGHT Gray to brown, uneven lesions progressing downwards. SHEATH BLIGHT Large, irregular lesions with dark brown margin and gray center. BROWN SPOT Circular to oval dark brown spots with brown margins and light gray center.
- 43. BACTERIAL LEAF STREAK Linear, water-soaked, yellowish streaks between the veins. RAGGED STUNT Leaves with ragged edge and twisted tip. Whitish galls on veins. TUNGRO Yellow to yellow orange leaves. Young leaf is mottled. GRASSY STUNT Light green, narrow, and erect leaves with numerous dark spots. Illustrated guide to disease symptoms on leaves
Editor's Notes
- In a study conducted by the International Rice Research Institute (IRRI), it was found that, on average, farmers lose 37% of their rice yield to pests and diseases, and that these losses can range between 24% and 41% depending on the production situation.
- narrow, dark-greenish, water-soaked, interveinal streaks of various lengths, initially restricted to the leaf blades. The lesions enlarge, turn yellowish-orange to brown (depending on cultivar), and eventually coalesce. -Chin Khoon Min Lesions begin as small, interveinal, water-soaked (dark green) streaks which later become translucent. Numerous tiny yellow beads of exudate are commonly found on the lesions. -T.W. Mew/IRRI Symptoms of severe damage on rice; the translucent streaks enlarge and coalesce turning light brown then greyish-white until the whole leaf dries up. -T.W. Mew/IRRI
- Planting resistant varieties has been proven to be the most efficient, most reliable, and cheapest way to control bacterial blight. Other disease control options include: Use balanced amounts of plant nutrients, especially nitrogen. Ensure good drainage of fields (in conventionally flooded crops) and nurseries. Keep fields clean. Remove weed hosts and plow under rice stubble, straw, rice ratoons and volunteer seedlings, which can serve as hosts of bacteria. Allow fallow fields to dry in order to suppress disease agents in the soil and plant residues.
- Initial symptoms appear as white to gray-green lesions or spots, with dark green borders. Older lesions on the leaves are elliptical or spindle-shaped and whitish to gray centers with red to brownish or necrotic border. Some resemble diamond shape, wide in the center and pointed toward either ends. Lesions can enlarge and coalesce, growing together, to kill the entire leaves. -IRRI rice knowledge bank
- Adjust planting time. Sow seeds early, when possible, after the onset of the rainy season. Split nitrogen fertilizer application in two or more treatments. Excessive use of fertilizer can increase blast intensity. Flood the field as often as possible. Silicon fertilizers (e.g., calcium silicate) can be applied to soils that are silicon deficient to reduce blast. However, because of its high cost, silicon should be applied efficiently. Cheap sources of silicon, such as straws of rice genotypes with high silicon content, can be an alternative. Care should be taken to ensure that the straw is free from blast as the fungus can survive on rice straw and the use of infected straw as a silicon source can spread the disease further. Systemic fungicides like triazoles and strobilurins can be used judiciously for control to control blast. A fungicide application at heading can be effective in controlling the disease.
- oval or ellipsoidal greenish gray lesions, usually 1-3 cm long, on the leaf sheath, initially just above the soil or water level in the case of conventionally flooded rice. under favorable conditions, these initial lesions multiply and expand to the upper part of the sheaths, the leaves, and then spread to neighboring tillers belonging to different hills (transplanted rice) or plants (direct-seeded rice). lesions on the leaves usually have irregular lesions, often with gray-white centers and brown margins as they grow older. in subtropical environments, the disease is mostly initiated by sclerotia (up to two million of which can be produced per square meter in a diseased crop).
- -use reasoned level of fertilizer adapted to the cropping season. -use reasoned density of crop establishment (direct seeding or transplanting). -carefully control of weeds, especially on the levees. -drain rice fields relatively early in the cropping season to reduce sheath blight epidemics. -use fungicide to treat seeds. -improve canopy architecture by reducing seeding rate or providing wider plant spacing. -Avoid high N-fertilization; split the application -K and Si fertilizers reduce disease incidence -Avoid close plant spacing -Apply fungicide (difenoconazole, iprodine, benomyl) on leafsheaths; if field was heavily affected in previous cropping -Deep plow to bury infected stubble and weeds -Expose affected soil to intense sunlight
- Use healthy seeds. Minimize insect infection of the rice crop in the field. Remove infected stubbles after harvest. Use optimum plant spacing. Sow 3 plants per hill at 20−30 cm row spacing. Apply potash at tillering stage. Apply foliar spray of calcium sulfate and zinc sulfate. Apply carbendazim, edifenphos, or mancozeb as seed treatment and foliar spraying at booting stage Apply benomyl and copper oxychloride as foliar sprays.
- Among the cultural control practices, burning straw and stubble or any crop residue after harvest or letting the straw decompose and draining the field can reduce sclerotia in the field. A balanced use of fertilizer or split application with high potash and lime to increase soil pH reduces stem rot infection and increases yield. The use of resistant cultivars may be the best control measure for stem rot. There are reported resistant cultivars from USA, India, Sri Lanka, Philippines, and Japan. Chemicals such as fentin hydroxide sprayed at the mid-tillering stage, thiophanate-methyl sprayed at the time of disease initiation can reduce stem rot incidence in the rice field. The use of other fungicides such as Ferimzone and validamycin A also show effectivity against the fungus.
- Use resistant varieties. Keep fields clean. Remove weeds and weedy rice in the field and nearby areas to prevent the disease to occur across cropping seasons. Use balanced nutrients If narrow brown spot poses a risk to the field, spray propiconazole at booting to heading stages. Use fungicide (e.g. azoxystrobin) for seed treatment.
- Use fungicides as seed treatments because the disease is commonly spread through spores on the surface of the seed, applying a fungicide containing benomyl or benomyl-t (at 1-2% of seed weight) for dry seed coating to treat infested seed can be effective. Soaking seed in a fungicide solution of 1:1000 for one hour or 1:2000 for five hours has also been shown to be useful. Avoid repeated applications of benomyl since the fungus can develop resistance to this treatment. In cases where resistance to benomyl occurs, use a fungicide that contains triflumizole, propiconazole, prochloraz or a combination of thiram + benomyl.
- Keep the field clean. Remove infected seeds, panicles, and plant debris after harvest. Reduce humidity levels through alternate wetting and drying (AWD) rather than permanently flooding the fields. Where possible, perform conservation tillage and continuous rice cropping. Use moderate rates of nitrogen. Use certified seeds. Resistant varieties have been reported. Treat seeds at 52°C for 10 min.
- Yellow or orange-yellow discoloration is noticeable in tungro-infected plants. Discoloration begins from the leaf tip and extends down to the blade or the lower leaf portion. Infected leaves may also show mottled or striped appearance, rust-colored spots, and inter-veinal necrosis. Tungro-infected plants also show symptoms of stunting, delayed flowering which may delay maturity, reduced number of tillers, small and not completely exerted panicles, as well as a higher than normal percentage of sterile panicles or partially filled grains, covered with dark brown blotches. The degree of stunting and of leaf discoloration varies with rice varieties, strains of the viruses, the age of the plant when infected, and with the environment. In varieties that carry some resistance to the disease, infected plants exhibit no discoloration or only a mild discoloration that may disappear as the plants mature. Tungro symptoms can be mistaken for physiological disoders. Specifically, the yellowing of the plant and its stunted height can be confused as nitrogen and zinc deficiencies and water stress pest infestation such as stem borer infestation, plant hopper infestation, and rat damage, and other diseases such as grassy stunt virus disease and orange leaf
- Once a rice plant is infected by tungro, it cannot be cured. Preventive measures are more effective for the control of tungro than direct disease control measures. Using insecticides to control leafhoppers is often not effective, because green leafhoppers continuously move to surrounding fields and spread tungro rapidly in very short feeding times. The most practical measures at present, include Grow tungro or leafhopper resistant varieties It is the most economical means of managing the disease. There are tungro-resistant varieties available for the Philippines, Malaysia, Indonesia, India, and Bangladesh. Contact your local agriculture office for up-to-date lists of varieties available. Practice synchronous planting with surrounding crops and farms Delayed or late planting, relative to the average date in a given area, makes the field susceptible for Tungro. Late-planted fields also pose a risk to early planting in the next season. Adjust planting times to when green leafhopper are not in season or abundant, if known Plow infected stubbles immediately after harvest to reduce inoculum sources, and destroys the eggs and breeding sites of green leaf hopper
- Plant variety with BPH resistance. Plow under infected plants and stubbles. Do not apply excess N-fertilizer. High intensity cropping leading to asynchronous planting favors disease outbreak. Monitor field and note increase in planthopper population
- Plant variety with BPH resistance. Plow under infected plants and stubbles. Do not apply excess N-fertilizer. High intensity cropping leading to asynchronous planting favors disease outbreak. Monitor field and note increase in planthopper population