Reproduced by:

Regional Agriculture and Fisheries Information DivisionDEPARTMENT OF AGRICULTURE

Regional Field Unit IXE-mail:rfu9da@yahoo.com

website:http://www.da.gov.ph

Source:Rice Technology Bulletin

Philippine Rice Research Institute (PhilRice)Science City of Muñoz, 3119 Nueva Ecija

Tel: (044) 456-0113, -0258, -0277Tel/Fax: (044) 456-0112; -0651 local 512;

-0652 local 515E-mail: prri@philrice.gov.ph

Website: http://www.philrice.gov.ph

• Usehealthytransplants.Makesurethatyourtransplantsdonothave galledroots.• Practicesolarization.Exposethesoiltothesunaftereachplowingand beforetheplowingtokillthenematodeandothersoilbornepathogens. Plowthefield15to30cmdeep.• Applyhighorganicmattersuchaschickenmanureandothercomposted materialsfromplantsandanimals.Highorganicmattersupporthigh populationofnematophagousfungiorfungithatfeedonnematodes. Chickendungalsoemitssubstancesfromtheammonificationofnitro- genouscompoundthataretonixtothenematodes.

• RemoveweedssuchasCyperus rotundus(purplenutsedge), C. iria (riceflatsedge),andTrianthema portucalastrum(horsepurselane) whicharegoodhostsofthenematode.• Grownon-hostcropsafteronionsuchashotpepper,cucumber, mungbean,andbushbeans.Othervegetablesthatarenon-hoststo M. graminicolaarebatao,bittergourd,bottlegourd,carrot,upland kangkong,pigeonpea,snapbean,spongegourd,andradish.• Practicefallowperiodforoneortwoseasons.• Afteronionproduction,growplantsantagonistictoriceroot-knotsuch asmarigold.• ApplyplantgrowthpromotingrhizobacteriasuchasBasilus subtilis as biocontrolagent.

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Introduction

Root-knotdiseaselocallyknownas“bukolsaugat”iscausedbysoil-bornenematodeofthegenusMeloidogyne spp. Meloidogynegraminicolaisthemostimportantspeciesofthisnematodeattackingriceparticularlyinrainfedanduplandecosystems.Thisspecieisquitedifferentfromotherroot-knotnematodesinricebecauseitcansurviveinfloodedfields,remainpassivewithinriceroots,becomeactiveupondryingofthesoil,andinfectthesucceedingsusceptiblecropsuchasonion.

Meloidogyne graminicolahasbeenreportedinmanyriceproducingcountriesinSoutheastAsia:Laos,Thailand,Bangladesh,Vietnam,Burma,andPhilippines.Itisapestinrainfedanduplandareas,andinlowlandfieldswithintermittentirrigation.Itslossesrangefrom20%inrainfedriceareasto70%inuplandecosystemsusingasusceptiblevariety.Hence,itsoccurrenceisnowrecognizedasathreatinfieldsusingaerobicricetechnology.

In1994,thepestwasdiscoveredtobeinfectingonionsgrownafterriceinCentralLuzonthroughPhilRice-IntegratedPestManagementCollaborativeResearchandSupportProgram,aUSAIDfundedproject.Thediseasehasbeenrecorded inmajorityof theonionfields (72%) in IlocosNorte,Pangasinan,NuevaVizcaya,andNuevaEcija.Thediseasewasalsodetectedin50%ofricefieldsinthecentralplains.

Root-knot nematode emerged as a serious pest problem in onion-producingprovinces. Thewidespreaddistributionofnematodepopulation,owingtocontinuouspracticeofrice-onionrotation,hindersamoreproductive

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• Removeweeds.Manydominant weedsinthericefieldsserveas alternatehostsofthisnematode, suchasEchinocloa colona (junglerice),E. glabrescens(barn yardgrass)Ludwidgia octavalvis (Longfruitedprimrosewillow),and Leptochloa chinensis(Chinese prangletop).

Echinocloa colona (jungle rice) with root galls

• Plowunderricestubbles.• Practicegoodtillage.Preparelandthoroughlybyplowingand harrowingthefield2-3times,allowingthesoiltobeexposedto thesunaftereachplowing.Thiswillalsoreduceweedhostsofthe nematode.• Removesoilleftinequipmentwhendoingfieldoperations.

Onion

• Ingrowingtransplants,applyvesiculararbuscularmycorrhizalfungi (VAM)intheseedbedbeforesowingonionseeds.VAMcanhelptheplantstoleratetheeffectofsoilbornepathogensincludingthericeroot-knotnematode.VAMalsoenhancerootgrowthandnutrientabsorption. Theyentertherootsandproducehyphaeorgrowing structuresthatalso extendoutsidetheroots. Theseroot“extensions”helptheplantstoabsorbmorenutrientsinthesoil,particularlyphosphorous.

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Apply management options before growing onions such as weeding of onion field and good land preparation to reduce nematode population at the early stage of the crop.

Root-Knot Nematode as Carry Over Pest

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ChannelsofTransmission:

• irrigationandrun-offwater • mudstickingtoanimals,machinery,peopleandinfectedplants • fieldsthatarenotfallowed • succeptibleonionvarietyplantedafterriceproduction

ManagementOptions

Themainobjectiveofnematodemanagementistopreventsignificantre-ductionincropyieldandtoreducenematodepopulationattheearlystageofthecropwhenbulbsarenotyetproduced.

An integrated program incorporating different options help rice-oniongrowersinkeepingthenematodepopulationsbelowdamaginglevels.Mana-gingroot-knotdiseasesismoreeffectivethroughawell-plannedandefficientlyimplemented cropping calendar. This calendar contains schedule for farmactivitiesforcropestablishmentuntilharvesttime.

Moreover,landpreparationshouldbethoroughlydonebeforerice-onionproductionasitprovidesthesoilconditionfavorableforplantgrowth.Thisalsofacilitateswater,nutrientsandpestmanagement.

RainfedRice

• Practicecroprotation.Grownon-hostcropssuchascorn,eggplant, melon,peanut,cowpea,orsquashbeforericeproduction.Afterrice croppingseason,avoidgrowingonion,garlic,mustard,pechay,soy beans,wingedbeans,okra,tomato,bellpepper,greenpeas,andwheat sincetheyaregoodhostsofthenematode.• Floodthefieldafterriceharvestorbeforelandpreparationtoreduce nematodepopulationinthesoil.• UseresistantricevaritiessuchasIR72,IR68,UPLRi-7,LubangRed, Salumpikit,Vandana,andToride.UPLRi-5isverysusceptibletoM. graminicola.

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Nematode juveniles become active in saturated soil

Second-stage nematodejuveniles infectsucceeding crop

Nematode reproducesin onion roots

Nematode in rice rootsremains inactive in flooded rice areas

Signs and Symptoms

Ricegrowninintermittentlyfloodedsoil,rainfed,anduplandecosystems• unevencropstand• wiltedplantsinfieldwithsufficientsoilmoisture• yellowingofleaves• stuntedgrowth• reducedtillering• earlyfloweringandreducednumberofpanicles• shortroots• hooked-likeinfectedroots.Sizeofgallsmayvaryfrom0.3-0.55mmlongand0.15-0.45mmwideto13mmlongand2.29mmwide, dependingontherateofinfection.Thegallsproducedonlowland riceareusuallybiggerthanthoseontherainfedrice,althoughmore gallsareproducedinthelatter

Roots with galls

Yellowing of rice leaves

Healthy rice(L) and infected plant (R) that is stunted and had reduced number of panicles

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Onionlpoorgrowthinsmallareasofthefield.Thisisthefirstsignof infestastionwhichlaterspreadinwiderareas.lbeadlikegallsthataresmallerthanricegalls.

Life cycle When the female lays its eggmasses, the life cycleof thenematode iscompleted.

Meloidogyne graminicola cancompleteitslifecyclewithin14-22days,whenthesurroundingtemperatureis28-320oC.Itsshortlifecycleinriceandonionrootspermitsittoproducelargenematodepopulationswithinasingleseason.

Thenematodepopulationincreasesrapidlyinricethaninonionprimarilybecausericeplantsproduceamorevigorousrootsystemonwhichthenematodefeeds.

Dissemination of the nematode

Meloidogyne graminicolacansurviveaseggsforlongperiodsinwater-loggedsoilandotheradverseconditions,orasjuvenilesforaslongasfoodsupplyisavailable.Withoutfood,thejuvenilescansurviveinthesoilforfivemonths.

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RICE

Nature of Damage

Thenematodeattackstherootsofplantsandcausesdirectdamage,orpredisposesplantstootherdiseases.Thesecauseswellingoftherootsorgallswhichblocktheflowofnutrientsnecessaryfornormalplantgrowth.Whenthesegallsarepulledapart,maturefemale,males,juveniles,andeggsmaybeobservedmicroscopically.

When the soil is infestedwithM. graminicola, it is not economical tocontinuouslygrowcropsonthesamefieldwithoutinterventions.

Effects on Yield

Rainfed Rice

Meloidogyne graminicolamay reduce yields of rice by 10% for every120nematodesper10-daysoldseedlings.Susceptiblericemayreducegrainyieldashighas70%,when375ormorejuvenilesarepresentaroundyoungseedlingofsusceptiblevariety. Infestationmayreducethegrain yieldofsusceptibleuplandriceashighas70%,iftheplantsarenotprovidedwithpropernutrition.

Lowlandvarietiesinirrigatedfieldstoleratethedamagebyproducingmoretillersandincreasingtheamountofrootsperhill.

Onion Bulbweightisreducedintothefollowingpercentages: • YellowGranex-40%.Bulbdiameterscanbereducedby75% onhigherlosses. • RedCreaole’s-85% • Batanes-60% • Tanduyong-31%Moreover,itsnumberofaggregatebulbsis reducedby48%.

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Whenthepopulationofnematodeishighduringthestartofcroppingseason,hostplantswithlessrootmass,maydie.

Yellow Granex onions with severe root galling

Reduced number and bulb size of Tanduyong (result of inoculation experiment in the greenhouse)

Life Cycle of Root-Knot Nematode Theroot-knotnematodestartstomultiplywithanegglaidbyafemale.Theeggsareusuallyheldtogetherinamassinagelatinousmatrix,whichiseitherpartiallyorcompletelyembeddedintheroots.Inrice,aneggmassmaycontainmorethan500eggs.

The nematode enters the firstlarvalorjuvenilestage(J1)developingandmolting inside the egg. Eventually, thejuvenileinitssecondstage(J2)emergesfrom the eggbypuncturing the eggshellusing its stylet. The stylet is an organfoundinitsmouththatisusedforpiercingplantcellstoobtainnourishment.J2movesthroughthesoilandthentowardstheroots.Itpenetratestherootsjustbehindtheroottips.Insidetheroots,J2migratesinbetweenand inside the cells through the cortex,untilitfindsafeedingsite.ThenematodegrowsinsizeandundergoesmoltingstagetobecomeJ3andJ4.

Whenthenematodesstartstofeedinsidetheroot,itbecomessedentary.Asitcontinuestofeed,itsbodysizeincreasesanddevelopsintoflask-shapedfemalesorintoelongatedmaleswithintheroottissueoftheplant.

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Egg of Meloidogyne graminicola with nematode’s first larval stage

Second larval stage near the root tip

Adult female feeding within the root tissue