common rice diseases (am sinohin)

DIAGNOSIS AND MANAGEMENT OF DISEASES IN RICE

A.M. SINOHIN

Crop Protection ClusterUP Los Baños

[email protected]

At the end of the session, participants should be At the end of the session, participants should be able to:able to:

1.1.Give their own definition of plant diseaseGive their own definition of plant disease

2. Know the causes of plant diseases and their 2. Know the causes of plant diseases and their characteristicscharacteristics

3. Know the three factors needed for the disease to 3. Know the three factors needed for the disease to occuroccur

ObjectivesObjectives

At the end of the session, participants should be At the end of the session, participants should be able to:able to:

4. Describe the specific symptoms and signs of 4. Describe the specific symptoms and signs of rice diseasesrice diseases

5. Know the art of plant disease diagnosis and the 5. Know the art of plant disease diagnosis and the importance of correct diagnosisimportance of correct diagnosis

6. Explain the principle of plant disease 6. Explain the principle of plant disease managementmanagement

ObjectivesObjectives

• LectureLecture• Power point presentationPower point presentation• Exercises:Exercises:

• Field collection and examination of Field collection and examination of disease specimen for signs and disease specimen for signs and symptomsymptom• Examination of pure cultures of Examination of pure cultures of pathogenpathogen

MethodologyMethodology

DIAGNOSIS AND MANAGEMENT OF DISEASES IN RICE

A.M. SINOHIN

Crop Protection ClusterUP Los Baños

[email protected]

National, average yield – 2.8t/ha

Asia, average yield – 3.6t/ha

World, average yield – 4.4t/ha

Rice StatisticsRice Statistics

Sources of Pressure for Higher Yield

• High population growth rate (2.5%)

• High per capita consumption (100 kg/yr)

• Declining area planted to rice

Strategies to Increase Production

• Increased cultivation of early maturing and short culm rice varieties

• High application rate of nitrogenous fertilizer

• High planting density

• Increasing cropping from 2 to 3 times per year

Common rice diseases in the Philippines

Sheath BlightSheath Blight

Causal organism :Causal organism : Rhizoctonia solaniRhizoctonia solani

Symptoms: Symptoms: Greenish gray lesions are first observed just above Greenish gray lesions are first observed just above the water leveling flooded field. the water leveling flooded field.

Under favorable conditions, the lesions expand to Under favorable conditions, the lesions expand to the upper part of the sheath and extend upward to the upper part of the sheath and extend upward to the leaves and then spread to neighboring tillers.the leaves and then spread to neighboring tillers.


Management Options Management Options At present, there is no resistant variety available for At present, there is no resistant variety available for cultivation. cultivation.

The main tools that are available to minimize sheath The main tools that are available to minimize sheath blight are prophylactic in nature including the blight are prophylactic in nature including the following:following:

Apply recommended rate of fertilizer- that has Apply recommended rate of fertilizer- that has to be adjusted according to the cropping to be adjusted according to the cropping

season and the risk of sheath blight outbreakseason and the risk of sheath blight outbreak


Management OptionsManagement Options The main tools that are available to minimize sheath The main tools that are available to minimize sheath blight are prophylactic in nature including the blight are prophylactic in nature including the following:following:

Density of seeding/planting has to be adapted Density of seeding/planting has to be adapted to cropping seasonto cropping season

Apply recommended fungicides at tillering Apply recommended fungicides at tillering and booting stage when symptoms appear.and booting stage when symptoms appear.

Rice BlastRice Blast

Causal organism :Causal organism : Magnaporthe oryzae/griseaMagnaporthe oryzae/grisea

Symptoms: Symptoms: The disease is found throughout the whole growth The disease is found throughout the whole growth stages of the rice plant. stages of the rice plant.

Leaf blast lesion is at first minute brown spots and Leaf blast lesion is at first minute brown spots and expands rapidly to spindle-shaped lesions; center expands rapidly to spindle-shaped lesions; center of the spot is usually gray or whitish with brown of the spot is usually gray or whitish with brown margin. margin.


Causal organism :Causal organism : Magnaporthe oryzae/griseaMagnaporthe oryzae/grisea

Symptoms: Symptoms: Node blast has black rotten node and breaks easily. Node blast has black rotten node and breaks easily. Neck blast may be confused with “white heads” Neck blast may be confused with “white heads” caused by stemborer. caused by stemborer.

Both injuries showed empty, erect white gray Both injuries showed empty, erect white gray panicle. panicle.

Unlike injury caused by stemborer, where the entire Unlike injury caused by stemborer, where the entire stem can be pulled readily, neck blast causes only stem can be pulled readily, neck blast causes only injury at the neck and does not extend further into injury at the neck and does not extend further into the leaf sheath.the leaf sheath.


Management OptionsManagement OptionsThe primary control option for blast is host-plant The primary control option for blast is host-plant resistance. resistance.

The disease can also be managed through the use The disease can also be managed through the use of diverse varieties with different levels of of diverse varieties with different levels of resistance and modified cultural practices. resistance and modified cultural practices.

In China, good control of panicle blast was In China, good control of panicle blast was achieved through interplanting varieties. In Japan, achieved through interplanting varieties. In Japan, the use multi-lines carrying different resistance the use multi-lines carrying different resistance genes have successfully used to manage the genes have successfully used to manage the disease.disease.


Management OptionsManagement OptionsSplit application of nitrogenous fertilizer and good Split application of nitrogenous fertilizer and good water management (flooding the soil) are water management (flooding the soil) are recommended to manage the disease.recommended to manage the disease.

Systemic fungicides are often used to control the Systemic fungicides are often used to control the disease in many rice growing areasdisease in many rice growing areas

Sheath RotSheath Rot

Causal organism :Causal organism : Sarocladium oryzae

Symptoms: Symptoms: Rot occurs in the uppermost leaf sheath enclosing Rot occurs in the uppermost leaf sheath enclosing the young panicle. the young panicle.

Lesions start as oblong or irregular spots with Lesions start as oblong or irregular spots with brown margin. and gray centers. brown margin. and gray centers.

Abundant whitish powdery growth may be found Abundant whitish powdery growth may be found inside infected sheaths. inside infected sheaths.


Causal organism :Causal organism : Sarocladium oryzae

Symptoms: Symptoms: Rotted growing panicle are incompletely exerted Rotted growing panicle are incompletely exerted with numerous empty grains Infected plants may with numerous empty grains Infected plants may be infested with stem borers. be infested with stem borers.

The disease is usually associated with virus The disease is usually associated with virus disease infectiondisease infection


Management OptionsManagement OptionsUse resistant variety. Use resistant variety.

To eradicate seed-borne pathogens causing the To eradicate seed-borne pathogens causing the disease, use Mancozeb and benomyl for seed disease, use Mancozeb and benomyl for seed treatments. treatments.

Systemic fungicide can be applied when typical Systemic fungicide can be applied when typical symptoms are observed on emerging panicle.symptoms are observed on emerging panicle.

BakanaeBakanae

Causal organism :Causal organism : Gibberella fujikuroi

Symptoms: Symptoms: The disease is commonly found throughout the The disease is commonly found throughout the whole growth stages of the rice plant. whole growth stages of the rice plant.

Infected seedlings elongates abnormally, becomes Infected seedlings elongates abnormally, becomes slender and the leaves turn pale yellow green. slender and the leaves turn pale yellow green. Infested plants develop roots at the upper nodes Infested plants develop roots at the upper nodes and the whole plant turns yellow. and the whole plant turns yellow.

At booting stage, some infected plants dieAt booting stage, some infected plants die

BakanaeBakanae

BakanaeBakanae

Management OptionsManagement OptionsUse resistant variety. Use resistant variety.

Since the causal organism is typically seed borne, Since the causal organism is typically seed borne, seed treatment with fungicide (e.g.benomyl or seed treatment with fungicide (e.g.benomyl or thiophanate methyl) is very effective in managing thiophanate methyl) is very effective in managing the disease.the disease.

Brown SpotBrown Spot

Causal organism :Causal organism : Helminthosporium oryzae

Symptoms: Symptoms: Typical spots on the leaves are oval, about the size Typical spots on the leaves are oval, about the size and shape of sesame seeds. and shape of sesame seeds.

They are relatively uniform and fairly evenly They are relatively uniform and fairly evenly distributed over the leaf surface. distributed over the leaf surface.

Young spots are small, circular (0.05 to 0.10mm in Young spots are small, circular (0.05 to 0.10mm in diameter) and usually dark brown. diameter) and usually dark brown.

Most spots have a light-yellow halo around their Most spots have a light-yellow halo around their margins.margins.


Management OptionsManagement OptionsSince the disease is known to be associated with Since the disease is known to be associated with soil deficient in nutrients, proper fertilization, good soil deficient in nutrients, proper fertilization, good water management and soil amendment are water management and soil amendment are suggested as management option.suggested as management option.

Narrow Brown SpotNarrow Brown Spot

Causal organism :Causal organism : Cercospora oryzae

Symptoms: Symptoms: The characteristic symptoms of the disease are The characteristic symptoms of the disease are usually observed during the late growth stages and usually observed during the late growth stages and are characterized by the presence of short, linear, are characterized by the presence of short, linear, brown lesions mainly on the leaves (although it may brown lesions mainly on the leaves (although it may also occur on leaf sheaths, pedicels, and glumes).also occur on leaf sheaths, pedicels, and glumes).


Management OptionsManagement OptionsFoliar fungicides such as mancozeb, benomyl, Foliar fungicides such as mancozeb, benomyl, propiconazole, and iprodione effectively suppress propiconazole, and iprodione effectively suppress this disease and may be economical if other this disease and may be economical if other diseases are also controlled along with narrow diseases are also controlled along with narrow brown spot.brown spot.

Bacterial Leaf BlightBacterial Leaf Blight

Causal organism :Causal organism : Xanthomonas oryzae pv. oryzae

Symptoms: Symptoms: Lesions start at the edge near the tip of the leaves. Lesions start at the edge near the tip of the leaves.

The young lesion expands along the vein forming The young lesion expands along the vein forming yellow streak. yellow streak.

The edge of the lesion is usually irregular or wavy The edge of the lesion is usually irregular or wavy and has a yellow margin. and has a yellow margin.


Causal organism :Causal organism : Xanthomonas oryzae pv. oryzae

Symptoms: Symptoms: As the disease advances, the lesion covers the As the disease advances, the lesion covers the entire blade, turn straw colored and later become entire blade, turn straw colored and later become grayish from the growth of various saprophytic grayish from the growth of various saprophytic fungi.fungi.


Management OptionsManagement OptionsResistant variety has been the most effective and Resistant variety has been the most effective and cheapest tool to manage the disease. cheapest tool to manage the disease.

Cultural practices (i.e. good drainage, balanced Cultural practices (i.e. good drainage, balanced amount of plant nutrients, nitrogen in particular) amount of plant nutrients, nitrogen in particular) clean culture (e.g. removing weed hosts and other clean culture (e.g. removing weed hosts and other possible sources of inoculum) and fallowing field to possible sources of inoculum) and fallowing field to dry in between cropping season are some control dry in between cropping season are some control option against the disease.option against the disease.

Bacterial Leaf StreakBacterial Leaf Streak

Causal organism :Causal organism : Xanthomonas oryzae pv. oryzicola

Symptoms: Symptoms: Symptoms begin with fine translucent streak Symptoms begin with fine translucent streak between veins. between veins.

As the disease progresses, the streaks becomes As the disease progresses, the streaks becomes yellowish-gray, the lesion coalesce, then eventually yellowish-gray, the lesion coalesce, then eventually turn to brown to grayish white causing the leaves to turn to brown to grayish white causing the leaves to die.die.


Management OptionsManagement OptionsThe use of resistant varieties is the most effective The use of resistant varieties is the most effective method of controlling the disease. method of controlling the disease.

Apply balanced level of plant nutrients, especially Apply balanced level of plant nutrients, especially nitrogen. nitrogen.

Draining the field when symptoms start to appear Draining the field when symptoms start to appear helps minimize the spread of the disease.helps minimize the spread of the disease.

RiceTungroRiceTungro

Causal virus :Causal virus : RNA virus - rice tungro spherical

virus (RTSV)DNA virus - rice tungro bacilliform

virus (RTBV)

RTBV depends on the helper produced by RTSV for its transmission.

It is the RTBV which is mainly responsible for the severe tungro symptoms.

Rice TungroRice Tungro

Symptoms: Symptoms: Rice plants infected by both RTBV and RTSV show Rice plants infected by both RTBV and RTSV show typical tungro symptoms: stunting and yellow or typical tungro symptoms: stunting and yellow or orange-yellow discoloration of the leaves. orange-yellow discoloration of the leaves.

Panicle exertion of infected plants is delayed and Panicle exertion of infected plants is delayed and often incomplete and some panicles become short often incomplete and some panicles become short and produce sterile or partially filled grains. and produce sterile or partially filled grains.


Symptoms: Symptoms: Plants that are infected with RTBV alone develop Plants that are infected with RTBV alone develop symptoms that are similar to but milder than those symptoms that are similar to but milder than those by both RTBV and RTSV. by both RTBV and RTSV.

Plant infected with RTSV alone may be symptom Plant infected with RTSV alone may be symptom less or exhibit only very mild stuntingless or exhibit only very mild stunting


Management OptionsManagement OptionsThe most practical method of tungro management The most practical method of tungro management

are: are: use of cultural practices (cultural control) use of cultural practices (cultural control) resistant varieties (host-plant resistance) resistant varieties (host-plant resistance)

Cultural practices (cultural control) involve the Cultural practices (cultural control) involve the following:following:

1. timing of planting: when both the 1. timing of planting: when both the viruliferous viruliferous GLH population and tungro GLH population and tungro incidence are lowincidence are low


Management OptionsManagement Options


2. synchrony of planting: establishing rice 2. synchrony of planting: establishing rice crops at about the same time to reduce the crops at about the same time to reduce the spread of tungro.spread of tungro.

3. plowing under infected stubbles to destroy 3. plowing under infected stubbles to destroy source of inoculum.source of inoculum.




4. direct seeding; tungro incidence is often 4. direct seeding; tungro incidence is often lower in direct seeded rice; dense plant lower in direct seeded rice; dense plant population reduce the chances for GLH to population reduce the chances for GLH to find and feed on diseased plants.find and feed on diseased plants.

RTSV resistant and RTBV tolerant varieties in the Philippines (IRRI, 2009)

VARIETY LINE NO. SOURCE OF RESISTANCE

REACTION TO TUNGRO VIRUSES

Matatag 1 IR69726-116-1-3 Utri Merah Resistant to RTSV

Matatag 2 IR69726-29-1-2-2-2 Utri Merah Resistant to RTSV

Matatag 3 IR 68305-18-1-1 Balimau Putih Tolerant to RTBV

Matatag 4 IR 68305-18-1-2 Balimau Putih Tolerant to RTBV

Matatag 9 IR73885-1-4-3-2-1-6 O. rufipogon Tolerant to RTBV

NSIC Rc 112 IR72102-159-1-3-3-3 O.barthii Resistant to RTSV

NSIC Rc 140 IR77298-5-6 Aday Sel Resistant to RTSV


Ragged StuntRagged Stunt

Causal virus :Causal virus :

Rice ragged stunt virus (RRSV) belongs to Reoviridae family

RRSV is transmitted in a persistent manner by BPH, Nilaparvata lugens


Symptoms: Symptoms: The primary symptoms are general stunting, ragged The primary symptoms are general stunting, ragged leaves with irregular or serrated edges, twisted leaves with irregular or serrated edges, twisted leaves and leaves are darker green in color. leaves and leaves are darker green in color.

These symptoms are generally exhibited during the These symptoms are generally exhibited during the tillering stagetillering stage

Grassy StuntGrassy Stunt

Causal virus :Causal virus :

Rice grassy stunt virus (RGSV) is a member of the Tenuivirus group.

RGSV is transmitted in a persistent manner by the brown planthopper (BPH) Nilaparvata lugens


Symptoms: Symptoms: Grassy stunt-infected rice plants show pronounced Grassy stunt-infected rice plants show pronounced stunting and proliferation of short, erect, and stunting and proliferation of short, erect, and narrow leaves that are pale green or pale yellow.narrow leaves that are pale green or pale yellow.

Ragged & Grassy StuntRagged & Grassy Stunt


The use of resistant varieties for ragged stunt The use of resistant varieties for ragged stunt management is probably the most important management is probably the most important control measure. control measure.

However, BPH-resistant cultivars, which formerly However, BPH-resistant cultivars, which formerly had little or no ragged stunt, often showed had little or no ragged stunt, often showed infestations when populations of BPH became infestations when populations of BPH became adapted to the resistant cultivars.adapted to the resistant cultivars.



Insecticides can be used to control ragged stunt by Insecticides can be used to control ragged stunt by drastically reducing BPH populations, which drastically reducing BPH populations, which otherwise may migrate to uninfected fields. otherwise may migrate to uninfected fields.

However, the logic of this strategy implies However, the logic of this strategy implies continuous pesticide application, and local continuous pesticide application, and local protection of a given field is in general ineffective protection of a given field is in general ineffective because of the very strong mobility of the vector.because of the very strong mobility of the vector.



Adjusting the timing and synchrony of crop Adjusting the timing and synchrony of crop establishment and the plowing under of infected establishment and the plowing under of infected stubbles are in general quite effective.stubbles are in general quite effective.

common rice diseases (am sinohin)

Technology

rice plant

rice blast causal organism

sheath blight causal

sheath rot causal organism

signs of rice diseases

definition of plant

management of diseases

neck blast