Rice _diseases _part_2_ collected and edited by Syed zahid. Read book for details.

1. Syed Zahid Hasan, SAU
Rice Diseases in Bangladesh
 PART - 2

2. Blast of rice
CO: Pyricularia oryzae
Damagetoplants
 development oflesions
 productionofchalkygrainsandunfilledgrains
 Riceblastis oneof themost destructive disease
 Allaboveground parts of the riceplant (leaves,leaf collar,culm,
nodes,neck,and panicle)are attackedby the fungus
 Depending on thesiteof symptom, riceblastisreferredas leafblast,
collarblast,node blast,neck orpanicle blast.Amongstwhich,neck
blastis the mostdestructive phase of the disease
 Yield lossesrangingfrom50 - 85%, under extremecases100%
Economic important

3. Symptoms
 lesionson the leaves are ellipticalor spindle-shapedand
whitishto graywithbrownishor necroticborder
 Lesions on the leaves may enlarge and coalesce to kill the
entire leaves
 Lesions on the collar are brown to dark brownand can kill
the entire leaf blade
 Lesions on the node are blackish to grayish brownand
causes the culm to break at the infected node
 Lesions on the neck are grayish brown and causes the
girdling of the neck and the panicle to fall over

4. lesionsontheleaves are
elliptical orspindle-shaped
andwhitishtograywith
brownishornecrotic border
Lesionsonthe
collar arebrown
todarkbrown

5. Lesionsonthe node
areblackishtograyish
brownandcausesthe
culmtobreakatthe
infectednode
Lesionsonthe
neckaregrayish
brownandcauses
the girdlingofthe
neckandthe
panicle tofall over
Conidia&Conidiophore
ofPyriculariaoryzae

6. Factors favoring disease development
 Low night temperature(22to28°C)
 High relative humidity(>95%)
 Extendedleafwetnessperiod (>10hrs)
 Cloudy and drizzlingweather
 Soil fertility(HighN)
 Presenceof theblast spores inthe airthroughout theyear
 upland riceenvironment and high elevation inthetropics
(becauseof low silicaaccumulationin upland soil)

7. Disease cycle

8. Control measures
 Plantingresistantvarieties,Eg. BR-3,BR-4,BR-6,BR-8,IR-22
 Use of disease freeseeds
 Raisingseedlingunderlowlandcondition
 Excessive use of fertilizershould be avoided
 BeforesowingseedtreatmentwithAmistarToporTrooper75WPor
Zeal75WPorMela75WPorNativo75WP@3g/kgseedsorFilia
525SE@5ml/kgseeds
 ApplicationofAmistarToporAdarsho75WPorStanza75WPor
Trooper75WPorZeal75WPorMela75WPorNativo75WPor
Novita75WGorDifa75WP@2g/litofwaterorFilia525SE@2ml/lit
ofwaterat12-15days intervalfor2-3timesinthefield

9. Sheath blight
CO: Rhizoctonia solani
Damage to plants
 formationof lesions
 productionof emptygrains
Economic important
 Sheathblight isconsideredtobe animportantdisease
next toriceblast
 It isan increasingconcernforriceproductionespecially
in intensifiedproductionsystems
 The diseasecauseda yield loss of (20-25)%
 Yield loss of 50%wasreportedwhensusceptible
cultivarswereplanted

10. Symptoms
 Initiallesions are small,ellipsoidalorovoid, greenish-grayandwater-
soakedand usuallydevelop nearthewaterline inlowland fields
 Olderlesions are ellipticalor ovoid witha grayish whitecenterand
light browntodark brownmarginlook like the skinof cobrasnake
 Lesions may reachthe uppermostleafunder favorable conditions
 Lesions may coalesceformingbiggerlesionswithirregularoutline
and may cause thedeathof thewholeleaf
 Severely infectedplantsproducedpoorly filledorempty grains,
especiallythoseon thelowerportionof thepanicles

11. Initial sheath blight
symptoms usually
occur as water-soaked
lesions on the first
leaf sheath
Sheath blight
on panicles
Older lesions are
elliptical or ovoid
with a grayish
white center and
light brown to dark
brown margin look
like the skin of
cobra snake
Sclerotia on
sheath blight
affected plant

12. Factors favoring disease development
 presenceof the diseasein the soil
 presenceof sclerotiaor infectionbodies floatingon thewater
 relative humidity from96 to100%
 temperaturefrom28-32°C
 high levels of nitrogenfertilizer
 close planting
 presenceof irrigationwater
 growingof high yielding improved varieties
 latetilleringor earlyinternodeelongationgrowthstages

13. 1- Overwintering sclerotia
in the soil;
2- Sclerotia which floated
on the surface of the
paddy field water during
soil puddling come in
contact with the rice plant;
3- Sclerotium germinating
and infecting host;
4- Disease developing in
horizontal and vertical
directions;
5- Characteristic lesion
developed on the sheath.
Disease cycle

14. Disease cycle

15. Control measures
 Avoid closerplantspacingordensecrop
 Need-basedorreal-timeapplicationofnitrogenfertilizer
 Infectedfieldshouldbedrain out
 Removal ofinfectedstubbles,cropresidues&weedfromthefield
 Plantingmoderatelevel ofresistancevarietysuch asBR-5,IR-26,BAU-63
 Duringlandpreparationapply ofKnowin50WPorAimcozim50WPor
Genuine50WPorAgridazim50WPorTurbo50WPorAwal72WPor
Dimbazim50WPorForastin50WP@1kg/haofland.
 Applicationof Score250ECorFolicur250EWorProud25EC orPotent250
EC orShadid250ECorTilt250EC orAkonazol250EC orHexa5ECor
AmistarToporNustar40EC orKrizole5EC @2ml/litofwaterat12-15days
intervalfor2-3timesinthefield

16. Sheath rot
CO: Sarocladium oryzae
Damage to plants
 Development of spotsor lesions
 Unfilledand discoloredpanicles
 reducesgrain qualityby causing paniclestorot and grains
to become discolored.
Economic important
 Sheathrot infectsthe rice plantat allgrowthstages,but it is most
destructivewheninfectionoccurs duringor afterthe bootingstage,
beforethe emergenceof the panicle
 It causesyield lossesfrom(20-50)%

17. Symptoms
 The typical sheathrot lesion startsatthe uppermost leafsheath
enclosing the young panicles
 It appearsoblong or as irregularspotwithdark reddish,brown
margins,and gray centeror brownishgray throughout
 Usuallyseveralspots are observed and thesespots enlargeand
combine or grow togetherand can cover mostof theleafsheath
 Paniclesremainwithinthesheathormay partiallyemerge.Affected
leafsheathsmay have abundantwhitishpowderyfungalgrowth
(mycelium) visible on theoutersurface
 Paniclesthathave not emergedrot andthe floretsturnred-brown
todark brown
 Infectedpanicles sterile,shrivelled, orwithpartiallyfilledgrain

18. typical sheathrotlesionattheuppermost
leafsheathenclosingtheyoung panicles
several spotsareenlarge
andcombineorgrow
together andcover most
oftheleafsheath
Paniclesremainwithinthe
sheathormaypartially
emerge.Affected leaf
sheathshave abundant
whitishpowderyfungal
growth(mycelium) visible
ontheoutersurface
Paniclesthat
have not
emergedrot
andtheflorets
turnred-brown
todarkbrown

19. Factors favoring disease development
 associated with insect injury
 presence of entry points
 high amount of nitrogen
 high relative humidity
 dense crop growth
 temperature from 20 to 28°C
 heading to maturity rice crop stages

20. Control measures
 Use healthyseeds
 Minimizeinsectinfestationinrice field
 Remove infectedstubblesafterharvest
 Use optimumplant spacing
 Applypotashat tilleringstage
 Apply foliarspray of calciumsulfateand zinc sulfate
 BeforesowingseedtreatmentwithKnowin50WPor
Aimcozim50WPor Genuine50 WPor @ 3 g/kgseeds
 Applicationof Folicur25 EC orEdifen 50EC orKrizole5EC @
2ml/litofwateror Knowin50WPorAimcozim50WPor Genuine
50 WPorNativo 75 WP@ 2g/litofwaterat 12-15days interval
for2-3timesin the field

21. Stem rot
CO: Sclerotium oryzae
Damage to plants
 formationof lesions
 productionof chalkygrains and unfilledpanicles
Economic important
 The infectionis seenon the ricecrop duringearlyheading and
grainfilling
 The leafsheathsdecay and causelodging and lowergrainfilling
 It cancause heavy lossesin manycountries.For example,In
Vietnam,thePhilippines, andIndia, lossesfrom30%to80%were
recorded

22. Symptoms
 Initial symptoms are small, irregular black lesions on
the outer leaf sheath near water level
 Lesions expand as the disease advances
 Visible numerous tiny white and black sclerotia and
mycelium inside the infected culms
 Infected culm lodges and caused unfilled panicles and
chalky grain
 Severe infection causes tiller death

23. small, irregular black
lesions on the outer
leaf sheath near
water level
numerous tiny white
and black sclerotia
and mycelium inside
the infected culms
Expand
lesions

24. Factors favoring disease development
 presenceof infectionbodies or sclerotiain theupper soil
layer or on irrigationwater
 presenceofwoundsas entrypoints of thefungus
 paniclemoisturecontent
 excessive nitrogenand low potashfertilizer
 rice steminfestedwithstemborer
 presenceof thewhitetipnematode,whichhas synergistic
effectwiththe disease
 frommilkingtoripeningstagesof the crop

25. 1- Stubbles with sclerotia
inside the stem;
2- Shreaded sclerotia
in the soil;
3- Sclerotia floating in water
during pudding soil;
4- Sclerotia got attached to
leaf sheath at water line;
5- Black lesions around
water line;
6- Minute sclerotia formed
inside stem.
Disease cycle

26. Control measures
 Use resistantcultivars,eg.BR-2,BR-3,BR-5,BR-12,BR-14,etc
 Burnstraw andstubbleorany cropresidueafterharvest
 Drainthe fieldtoreduce sclerotia
 Balancethe use of fertilizeror performsplitapplicationwithhigh
potashandlime toincreasesoilpH
 Chemicalssuch asfentinhydroxide sprayed at the mid-tilleringstage,
thiophanate-methylsprayed atthe time of diseaseinitiation
 Applicationof Ferimzoneor validamycinA@ 2g/lit ofwaterat 12-15
days interval for2-3 timesin thefield

27. False smut
CO: Ustilaginoidea virens
Damage to plants
 reductionin seedgermination
 chalkinessof grains - reductionin grainweight
 The diseasecauseschalkinessand canreduce grainweight
 It alsocausesa reductionin seedgerminationof up to 35%
 In dampweather,the diseasecanbe severe and lossescan reach25%
 In India,a yield loss of 7-75%wasobserved
Economic important

28. Symptoms
 Individual rice graintransformedintoa mass of velvety spores or yellow
fruitingbodies
 Growthof velvety sporesenclose floralparts
 Immaturespores slightlyflattened,smooth,yellow,andcovered by a
membrane
 Growthof spores resulttobrokenmembrane
 Maturesporesorange and turnyellowishgreenorgreenishblack
 Only few grainsin a panicleare usually infectedand the restare normal

29. Immature sporesslightlyflattened,
smooth, yellow, andcovered bya
membrane
Maturesporesorange
andturnyellowishgreen
orgreenishblack

30. Factors favoring disease development
 presenceof rainand high humidity
 presenceof soilswithhigh nitrogencontent
 presenceofwindfordisseminationof the sporesfromplant toplant
 presenceof overwinteringfungus as sclerotiaand chlamydospores
 floweringstage of the ricecrop

31. Disease cycle

32. Control measures
 Keepthe fieldclean
 Remove infectedseeds,panicles,and plant debrisafter harvest
 Reduce humidity levels throughalternatewettinganddrying
 Use moderateratesof Nitrogen
 Use certifiedseeds
 Use resistantvarieties
 Treatseeds at52°C for10 min
 Applicationof Bavistin DFor Knowin50WPorGenuine 50 WPor
Turbo50 WP@ 2g/lit ofwaterat 12-15days intervalfor2-3times
in thefield

33. Bakanae or foot rot
CO: F. moniliforme, Gibberella fujikuroi
Damage to plants
 abnormal plant growth
Economic important
 Bakanaeis widelydistributedin allrice-growingareas
 Its namevaries in differentcountries.In thePhilippines it iscalled
as palay lalake(male rice);in China,whitestalkandin Guyana,
man rice.In India,describedit as foot rot disease
 Loss reportsvarywidely,3.7- 50.0%. In Japan,20%to50%loss
wasobserved.Yieldlosses of 15%and 3.7%werereportedin
India and Thailand,respectively.

34. Symptoms
 The mostconspicuous symptom of bakanae is the appearanceof
abnormallyelongated,slender,paleseedlingsdue toexcessive
elongationof the lowerinternodes
 Infectedseedlings may, however,alsobe stuntedand chlorotic,
exhibitingroot and crownrot.Infectedseedlingsusuallyare killed
 Olderplants canalsobe infectedand may exhibitabnormalelongation
and produce adventitious rootsat the lowernodes of the culm
 Plants thatsurvive untilmaturityare sterileand produce no panicles or
emptypanicles

35. appearanceofabnormally
elongated, slender,pale
seedlingsduetoexcessive
elongationofthelower
internodes
adventitious
rootsatthe
lowernodes
oftheculm

36. Factors favoring disease development
 presence of infected seeds
 soilborne pathogens
 damp soil condition
 high nitrogen application
 temperature ranging from 30 to 35°C
 High humidity and cloudy weather during heading stage
 presence of wind or water

37. Disease cycle
1 - Infected seed and crop
residues as primary source
of infection;
2 - Infected plant (ip) with
adventitious roots (ar) at
upper nodes and healthy
plant (hp). Diseased plant in
tall with narrow leaves;
3 - Conidiophores and
conidia on the diseased
area;
4 - Grain infection by air-
borne conidium.

38. Control measures
 collectseedfromdiseasefreearea
 Thin and abnormallyelongatedpale greentillershould be uprooted
and destroyed by burning
 Use resistantvarieties
 Saltwatercan be used toseparatelightweight,infectedseeds from
seed lots andtherebyreduce seedborne inoculum
 Seed treatmentwithUnisaaf75WPor Knowin50WPor Genuine50
WP@ 3g/kgseeds orProud 25 EC orProven 250 EC orPropicon
250 EC or Filia525 SE @ 5ml/kg seeds
 ApplicationofUnisaaf75WPor Knowin50WPorGenuine 50 WP@
2g/litof waterorProud 25 EC orProven 250 EC orPropicon 250 EC
orFilia 525 SE @ 2ml/lit ofwaterat 12-15days intervalfor2-3times
in the field

39. THANKS TO ALL