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PAGE 1plant parasiticnematodes fact sheetsouthern and western REGIONManaging cereal cyst and rootlesion nematodesRoot lesion nematode (RLN, Pratylenchus species) and cereal cyst nematode(CCN, Heterodera avenae) are significant pests that feed on the roots of crop plantsand cause yield loss.KEY POINTS■ CCN has one life cycle per seasonwhereas RLN is polycyclic withthree to five generations per year.■ CCN hosts are restricted tocereals and grasses whereas theRLN host range is broader andincludes cereals, oilseeds, grainlegumes, pastures and broad leafand grass weeds.■ A number of different RLNspecies are present, includingPratylenchus neglectus, thornei,penetrans and teres.■ Nematode type and species willaffect choice of managementpractices, particularly rotationoptions.Management of RLN and CCNin winter crops2009■ As a general rule, well-managed rotations with resistant or non-host break cropsare vital. Avoid consecutive host crops to limit populations.■ Choose varieties with high resistance ratings, which result in fewer nematodesremaining in the soil to infect subsequent crops.■ Reducing RLN and CCN can lead to higher yields in following cereal crops.■ Healthy soils and good nutrition can, to some extent, ameliorate RLN and CCNdamage through good crop establishment, and healthier plants recover morereadily from infestation.■ Observe crop roots to monitor development of symptoms.■ Weeds can host parasitic nematodes and control of host weed species and cropvolunteers is important.Table 1: Reaction of major crop and pasture species to Pratylenchus neglectus,P. teres and P. penetransP. neglectus P. teres * P. penetrans *SUSCEPTIBLE MODERATELY SUSCEPTIBLE RESISTANT SUSCEPTIBLE SUSCEPTIBLEWheat Barley Field Pea Wheat WheatCanola Oat Narrow-leafed lupin Barley OatChickpea Medic Faba and Narbon bean Oat Field peaMustard Durum wheat Lentil Canola Faba beanBiserulla Common vetch Lathyrus Narrow-leafed lupinTrigonella Triticale ChickpeaRyeDurum wheatSafflowerTriticaleClover and Lotus MODERATELY SUSCEPTIBLE MODERATELY SUSCEPTIBLELegume pastures** Narrow-leafed lupin BarleyField peaCanolaTriticale*Information for P. teres and P. penetrans is based on samples received by AGWEST Plant Laboratories for diagnosis,combined with data from preliminary field and glasshouse trials.** Clover, Bitter vetch, Yellow serradella, French serradella, Sulla and Lotus. Source: VA Vanstone, DAFWA.Level 1, Tourism House | 40 Blackall Street, Barton ACT 2600 | PO Box 5367, Kingston ACT 2604 | t. +61 2 6166 4500 | f. +61 2 6166 4599 | e. grdc@grdc.com.au | w. www.grdc.com.au

PAGE 3The life cycle of RLNRLN is a migratory plant parasiticnematodes, meaning they migratefreely between roots and soil providingthe soil is moist. The life cycle ofRLN begins after the opening rains inautumn. Juvenile and adult nematodesrehydrate, become active and invadeplant roots where they feed andmultiply as they move through the root.Individual eggs are laid within the rootfrom which juvenile nematodes hatch,grow to adults and lay eggs. Theremay be three to five cycles within theplant host each season. As plants andsoil dry out in late spring, RLN enters adehydrated state called anhydrobiosisand can survive high soil temperaturesand desiccation over summer.As nematodes feed and multiply,lesions and/or sections of browndiscolouration are formed on the plantroot. Other symptoms include thereduction in the number and size oflateral roots and root hairs.Management of RLNThe most important management toolis good rotations. In heavily infestedpaddocks break crops should be grownfor one or two years to decrease thepopulation. Resistant varieties shouldbe selected for the following years.Adequate nutrition (especially nitrogen,phosphorus (P) and zinc) normallyallows plants to better tolerate plantparasitic nematodes, although this doesnot necessarily lead to lower nematodereproduction. Field trials in areasinfested with P. neglectus have shownyield losses for intolerant wheat rangedfrom 12 to 33 per cent when minimallevels of P were applied but losses werereduced to only five per cent with a high(50 kilograms per hectare) rate of P.Weeds can play an important rolein the increase or persistence ofnematodes in cropping soils. Thus,poor control of susceptible weedscompromises the use of crop rotationsfor RLN management.Wild oat, barley grass, brome grassand wild radish are susceptible toP. neglectus.When a pasture is included in thecropping rotation, weeds stronglyinfluence nematode populations at theend of the pasture phase.Manage volunteer susceptible cropplants that can harbour nematodes.Nematodes cannot move greatdistances unaided. However, theycan be spread by surface water, andin soil adhering to vehicles and farmmachinery. In uninfested areas, goodhygiene should be adopted. They canalso be spread in dust when they are ina dehydrated state over summer.CultivationSince RLN is vulnerable to deaththrough soil disturbance while inits dehydrated state, mechanicaldisturbance through tillage has beenconsidered as a method of reducingnematode populations. However, tillageof dry soil is not an option in southernor western Australian farming systemsas this would expose the soil to winderosion and also result in the loss ofvaluable soil moisture.FIGURE 1 ROOT LESION NEMATODERoot system ofhealthy plantNematodeinvadingrootcortexAdultsNematodes penetrateroots directly4thmolt3rdmoltIV StagelarvaeIII StagelarvaeII Stagelarvae2ndmoltII Stagelarvae1stmoltI StagelarvaeLarvae and adultsattack rootsEggsEggs are laid orreleased in soilReduced rootsystem and lesionson roots of infectedplantNematode leavesdecaying rootsand attacks new rootsYoung roots may begirdled and theirdistal portions killedSome nematodesleave the lesionand attack otherrootsInvadedtissuesturnbrownNematode reproducesand migrates withinthe rootInvaded corticaltissues collapseand break downSource: Agrios GN, Plant pathology 4th edition. Academic Press: New York and London, 1997.

PAGE 4About the cereal cyst nematodeOnly one race of CCN, Heteroderaavenae, occurs in Australia and itcauses cereal crop damage in WesternAustralia, South Australia, SouthernNSW and Victoria.It affects wheat, barley, oat and triticalevarieties and can cause yield loss ofup to 80 per cent in intolerant varieties.Barley varieties are tolerant, whereaswheat, and particularly oat, rangesignificantly from moderately tolerant tovery intolerant depending on the variety.The symptomsThe symptoms of CCN infection arereadily recognised. Above-ground,patches of yellowed and stuntedplants can be observed. Planting asusceptible crop in successive yearswill result in these patches becominglarger with time. Below-ground, wheatand barley roots will be ‘knotted’,and oat roots appear ‘ropey’ andswollen. Development of root systemsis retarded and shallow. In spring, thecharacteristic pinhead-sized ‘whitefemales’ can be seen, particularly onsusceptible plants, with the naked eyeif roots are carefully dug and washedfree of soil.CCN is a sedentary plant-parasiticnematode which means after invasionof the host it sets up a fixed feedingsite within the plant root. The life cycleof CCN, which has one generation perAlthough the majority of barley varietiesare tolerant to CCN, they can still besusceptible. Although the tolerantbarley crop will not be affected by thenematodes, they can still reproduceif that crop is susceptible, leavinghigh populations in the soil to infect asubsequent crop.If CCN is a problem, the best choiceis to grow a cereal variety that is bothresistant and tolerant to the nematode.year, can be thought of as four stagesbeginning as an over summering stageas a brown cyst containing 200 to 300eggs. Only 70-80 per cent of eggshatch in the first year, regardless ofconditions, leaving some in reservefor the second year which will infect afuture host crop if planted.The brown cyst develops from theswollen body of the female nematodeas the crop matures in the previous latespring. Each cyst is approximately onemillimetre in diameter and is coveredwith a hard, brown outer casing whichenables the eggs to survive in soil overthe hot dry Australian summer.After opening rains (April-June),and when soil temperatures dropto 15 degrees C or below, juvenilenematodes hatch from the cyst andCCN infested paddocks (regions) insouthern Australia are now relativelyrare following the widespread adoptionof rotations using resistant cereals andnon-host crops.If CCN is present at moderate to highlevels growers need to implementrotations using tolerant and resistantcereals and non-host crops for at leasttwo years and then monitor nematodelevels before considering the use ofsusceptible varieties.invade host plants. Each nematodesets up a feeding site called a syncytia.Female nematodes remain feedingin the root and gradually swell in theprocess of producing eggs.The eggs are retained inside the bodywhich eventually bursts through to theoutside of the root. The white femalecan then be seen on the outside of theroots as a small cyst about the sizeof a pinhead and visible to the nakedeye. Resistant plants may have asmall number of white females presentwhereas susceptible plants may havelarge numbers where CCN is present ina paddock.The female nematode dies as the cropripens and forms a brown cyst thathardens and remains in the soil untilthe next season to complete the cycle.Resistant and tolerantSusceptible and tolerantResistant and intolerantSusceptible and intolerantsource: sardiVariety ratings for nematodesVarieties are rated according to theirtolerance or intolerance and theirsusceptibility or resistance to nematodes.The mechanisms of resistance and toleranceare different and need to be treated as such.■ Intolerance means the crop yields poorlywhen attacked.■ Susceptibility means nematode numbersincrease during the cropping season.■ Tolerance and intolerance ratingsindicate the effect nematodes will have onthe yield of the current crop.■ Resistance/susceptibility ratings indicatethe effect the crop variety will have onreproduction of the nematodes, and hencethe possible effect on the next crop via thenematode population remaining in the soilto infect the next crop.Pictured are four combinations of ratingsfor nematodes. Tolerance/intolerance =the effect on the yield of the current crop,Resistance/susceptibility = the effecton building nematode numbers and thecarryover to next year’s crop.

PAGE 5Management of CCNCCN is easy to manage which isevidenced by the widespread reductionin paddock CCN levels that has takenplace since the introduction of resistantvarieties and extension of managementstrategies. CCN is much easier tomanage than RLN because of thegreater range of resistant and non-hostcrops available.CCN only feeds on cereals and othergrasses. Wild oats are susceptibleso will multiply the CCN population,but other grasses are resistant andproduce low levels of CCN.The use of CCN-resistant cereals andnon-host crops such as pulses andoilseeds in rotation is the requiredmanagement strategy. Where CCNlevels are moderate to high the bestchoice is two years of resistant andtolerant cereal or non-host crops.The most profitable option will oftenbe chosen, but growers should alsobe mindful of management of otherdiseases and weeds when makingthese choices to produce longer-termprofits. While two years is generallyaccepted to reduce CCN to low levels,exceptions do occur. Monitoringpaddocks and the use of diagnosticservices to check CCN levels isencouraged. Less than five eggs pergram of soil can produce yield loss forintolerant cereals.If susceptible cereal varieties arecontinually used in a rotation CCN cancause ongoing significant yield losses.Soil testing can help ascertain the risk.Break crops must be maintained freeof wild oats and susceptible cerealvolunteers. The benefit of a two-yearbreak should be regarded as temporarybecause the nematode populationrises quickly when susceptible cerealsare returned to the system. Thesolution is not instant and it can takeseveral years to reduce high levels.CultivationCultivation exacerbates CCN damage,probably because it spreads cysts andhatched nematodes and/or facilitatesthe movement of nematodes to rootsby lowering soil bulk density.In contrast, there is less root damageunder reduced tillage. Since thereare also fewer white females on rootsin non-till situations, there is lesscarry-over of cysts and eggs into thefollowing season. The widespreadadoption of no-till farming systems,along with the associated increase inrow spacing, has probably played arole in reducing losses from CCN.TestingIf cases of CCN or RLN infestationare suspected, growers are advisedto check the roots of the host crops.Carefully digging up, then simplywashing the soil from the roots of aninfected plant can sometimes revealevidence of infestation in the rootswhich warrants laboratory analysis.Testing services are available aroundAustralia and growers are advisedto contact their local agriculturaldepartment for advice.FIGURE 2 CEREAL CYST NEMATODEFemale beginsto produceeggsMaleleavesrootII StagelarvaeemergefromeggsFemale layseggs ingelatinousmass RootsurfaceSyncytia beginto degenerateFemalecyst filledwith eggsstill attachedto rootII Stage larvae ineggs inside brown cystoverwintering in soilAdult nematodes4th moltIV Stage larvae3rdmoltFemales at variousstages of developmentattached to root2ndmoltII Stage larvaeemerge fromcystII Stagelarvaefree insoilSyncytia of malebegins to degenerateII Stage male and female larvae II Stage larvae invades rootfeeding on syncytia and causes formation of syncytiaSource: GN Agrios, Plant Pathology, 4th edition, Academic Press, 1997.II Stage larvaeattack young rootsCCN cause roots to be retardedand shallow. Infected wheat andbarley roots will appear knottedand oats appear ‘ropey’ andswollen.

PAGE 6Frequently asked questionsQ. Why is my resistant cerealshowing CCN root damage?Resistant cereals sown into apaddock with CCN will be attackedand penetrated at a similar rate as asusceptible variety causing the samedamage. Resistant cereals act bysuppressing the development of CCNin the root so very few can mature andcause multiplication whereas the CCNin the root of a susceptible variety willmature to produce large numbers ofCCN white females.Q. Can I spray for CCN or RLN?Nematicides provide significantimprovements in grain yield whenapplied to nematode-infested plots,but are no longer used commercially inAustralia. They are not recommendedbecause of their cost and inherentmammalian toxicity, and also becauserotational crops are available fornematode management. If they wereused commercially, it is likely theirefficacy would be poor, particularly insituations where the nematode occursat depth.Currently, no nematicides areregistered for use on broadacre cropsin Australia.Q: Is CCN ever likely to be amajor problem in Australianfarming again?Yes. In SA and Victoria, thewidespread adoption of resistantcereal varieties and non-host rotationshas significantly reduced the problem.However, if susceptible varieties aregrown in continuous rotation, CCNlevels could easily increase again.Although CCN is less widespreadin WA than in SA or Victoria, manyWestern Australian cereal varietiesare susceptible to CCN. Intensivecultivation of susceptible cereals canlead to significant increase in CCNlevels. So it is not a major problemat the moment but could be again ifprecautions are not taken, much thesame way some human diseasescould increase if inoculation programswere to stop.Q: Does timing of sowing help?There is limited information on theaffect of time of sowing on the yieldloss to intolerant crops in the presenceof RLN. Trials in the northern regionhave shown later sown wheat cropscan be more severely affected thanthose sown early. In Victoria, sowingin mid July compared with late Mayresulted in 60 per cent lower yield foran intolerant wheat variety, and 10 percent lower yield for a tolerant varietywhere there was a high population ofP. thornei.Q: Could P. teres and P. penetransspread to other states?P. teres has only been identified incrops in WA and is not known to occurin other regions of Australia. In fact,P. teres is uncommon on broadacrecrops anywhere in the world.P. penetrans does occur in otherstates, although it is generally knownas a horticultural pest.Useful resources:■ Dr Vivien Vanstone, DAFWA (08) 9368 3141 Email vivien.vanstone@agric.wa.gov.au■ John Lewis, SARDI (08) 8303 9394 Email lewis.john@saugov.sa.gov.au■ PreDicta B – a soil analysis service delivered by accredited agronomists which can detect P. neglectus, P. thornei andCCN. This test is not currently able to detect P. teres and P. penetrans, so results need to be interpreted with caution,particularly for Western Australia. Contact your local agronomist or to locate your nearest supplier, email your contactdetails and location to:predictab@saugov.sa.gov.au■ Growing season tests can be carried out on affected plants and associated soil through state departments■ Testing laboratories WA (08) 9368 3721 or agwestplantlabs@agric.wa.gov.auSA (08) 8303 9360, VIC (03) 5362 2111■ Cereal Root and Crown Diseases (2000), Hugh Wallwork, GRDC and SARDI■ DAFWA Bulletins www.agric.wa.gov.au■For variety ratings see state crop variety and disease guides published annuallyDisclaimerAny recommendations, suggestions or opinions contained in this publicationdo not necessarily represent the policy or views of the Grains Research andDevelopment Corporation. No person should act on the basis of the contents ofthis publication without first obtaining specific, independent professional advice.The Corporation and contributors to this Fact Sheet may identify products byproprietary or trade names to help readers identify particular types of products.We do not endorse or recommend the products of any manufacturer referred to.Other products may perform as well as or better than those specifically referredto. The GRDC will not be liable for any loss, damage, cost or expense incurredAcknowledgements: Dr Vivian Vanstone, DAFWA; John Lewis, SARDI.or arising by reason of any person using or relying on the information in thispublication.CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USEAny research with unregistered pesticides or of unregistered products reportedin this document does not constitute a recommendation for that particular use bythe authors or the authors’ organisations.All pesticide applications must accord with the currently registered label for thatparticular pesticide, crop, pest and region.produced by www.coretext.com.au