G44 Barley disease management guide - HGCA

Seedling blights– Microdochium nivale– Fusarium graminearumSymptomsThe most common symptom of a serious attack is poorplant establishment. Other symptoms include brownlesions on stem base, leaf blotch and ear blight.ImportanceUnlike wheat, poor seedling establishment in barleydue to Microdochium nivale is rare. Very high infectionlevels may cause seedling blight when seed is sown incold seedbeds. Losses are not as high as those seenfor wheat. Fusarium graminearum has the potential tocause seedling losses in barley but is currently rare.Life cycleInoculum is mainly found on crop debris (F. graminearum),and soil (M. nivale) or from seed infection. The resultantseedling blight or stem-base browning releases sporeswhich are splashed up the plant ultimately infectingthe ear.Risk factors– High level of seed infection.– Untreated seed or seed without appropriate treatment.– M. nivale: early sown spring barley.– F. graminearum: maize in the rotation.Seedling blight, foot rotand leaf spot– Cochliobolus sativusSymptomsEarly symptoms include brown roots and coleoptileswhich can cause seedling blight but more usuallyinfected plants grow to maturity. Affected plants showbrown spotting on lower leaves. Severe infections cancause stem-base rotting and poorly-filled ears.ImportanceCochliobolus sativus is traditionally a disease of hotterclimates than that of the UK but seedling losses andleaf spotting can occasionally occur.The disease is rare on winter barley but is more oftenrecorded on spring barley. Some varieties are moresusceptible than others. Infections tend to be higherin organic compared to conventional systems.Life cycleThe soil and seed-borne fungus survives on debris andgrass weeds. It sometimes causes seedling blight.More usually it infects roots but the plant survives. Leafspotting and stem-base infections produce splash-bornespores to infect seed in ears.Risk factors– Any factors that slow germination and emergence.– Poor seedbeds.– Extended periods of warm, moist weather.Net blotch– Pyrenophora teres f.sp.teres– Pyrenophora teres f.sp.maculata (spot form)SymptomsSymptoms can be similar to leaf stripe infection inemerging crops – the first leaf has a single stripeextending the full length of the leaf. Later leavesdevelop more characteristic lesions.ImportanceSeed-borne inoculum is usually much less importantthan infected stubble, though infected seed can startearly foliar epidemics which may damage yield.Risk factors– High level of seed infection.– Varietal susceptibility.Ramularia leaf spot– Ramularia collo-cygniSymptomsRamularia shows no visible symptoms at the seedlingstage. Identification within seed and leaves requiresmolecular diagnostics. Symptoms occur when leavesare stressed. Square brown lesions develop on themiddle or tips of leaves, surrounded by a yellow halo,on both sides of the leaf. Symptoms are similar to thespot form of net blotch, but the rectangular shape istypical of ramularia leaf spot.ImportanceSeed-borne inoculum is considered a major diseasesource.Risk factors– High level of seed infection.– Varietal susceptibility.– Wet weather at flowering.The barley disease management guide 2009 6

Rhynchosporium– Rhynchosporium secalisSeed treatment – To treat or not to treatSymptomsRhynchosporium colonises seed tissues and can bedetected by molecular and other methods. Underfavourable conditions, it can be transmitted frominfected seed to seedlings. Typical symptoms on leavesare pale water-soaked lesions that develop into typicalbrown necrotic patches with dark margins.Certified seedFarm-saved seedGermination test85% plus 78–84% Under 78%ImportanceSeed-borne inoculum can contribute to the start ofepidemics. Yield loss is associated with severesymptoms on upper leaves.Risk factors– Varietal susceptibility.– Wet weather from flowering onwards.– Proximity to debris from previous barley crops.See also page 12.YESTreat seed for loose smut, leaf stripe, net blotchand seedling diseases*. Test for covered smut isonly a requirement if present in growing crop.NODoes loose smutexceed 0.5%or 2% if farmsavedseed?Considering sowinguntreated?YESNOIs grain damaged,eg heat, glyphosate?NOYESDO NOTUSE FORSEEDNODoes leaf stripeexceed 2%?YESNONODoes net blotchexceed 10%?Do seedlingdiseases exceedadvisory standards(page 4)?YESYESTreat seed with anappropriate product(see page 8)*Leaf stripe, net blotch and seedlingdisease can all be determined from thesame agar plate test.NOVery low risk of seed-borne disease.Consider sowing seed untreated.The barley disease management guide 2009 7

Seed treatment – OptionsDiseasesPestsActive ingredient Product Barley loose leaf covered seedling net snow take- leaf slugs virus wire- wheatsmut stripe smut blight blotch mould all hoppers vectors worm bulb flycarboxin, thiramcarboxin, thiramAnchorAnchorspringwinterChemturaChemtura✓✓✓✓✓✓✓✓✓clothianidin, prothioconazole, Raxil Deter wintertebuconazole, triazoxide Bayerclothianidin Deter winterBayer✓ ✓ ✓ ✓ ✓✓✓✓✓✓✓✓✓fludioxonil Beret Gold springSyngenta winter✓ ✓ ✓ ✓fludioxonil, flutriafol Beret Multi springSyngenta winter✓ ✓ ✓ ✓ ✓ ✓fludioxonil, tefluthrin Austral Plus springSyngenta winter✓ ✓ ✓ ✓✓ ✓fluquinconazole, prochloraz Jockey winterBASF✓ ✓ ✓fuberidazole, triadimenol Tripod springMakhteshimAgan winter✓ ✓ ✓ ✓fuberidazole, imidacloprid, Tripod Plus wintertriadimenolMakhteshim ✓ ✓ ✓ ✓ ✓Aganipconazole Crusoe winterChemtura✓ ✓prochloraz, triticonazole Kinto springBASF winter✓ ✓ ✓ ✓prothioconazole, Raxil Pro wintertebuconazole, triazoxide Bayer spring✓ ✓ ✓ ✓ ✓silthiofam Latitude winter✓Monsanto✓ label recommendation ✓ some known activityThe barley disease management guide 2009 8

Winter barley spray timingEar numberGrain number per earPotential grain sizeCanopy sizeGrain growthTiller productionSpikelet productionGreen canopy productionTiller lossSpikelet lossCanopy senescenceGrain fillingEmergence Start of tillering GS23 GS30 GS31 GS32 GS39 GS49 GS59HarvestAutumnT0 Early spring T1 Stem extension T2 Flag leafemergence and bootingSubstantialtillering canoccur inthe autumnafter earlydrillingand/orduring a mild winter. An autumn sprayto such crops may give small, butsignificant, yield responses. Whereplant populations are moderate or highthe potential to increase ear numbersis greater.However, an early spring treatment ismore likely to produce an economicresponse.Early springtreatmentsprotectagainst foliardiseasesthat canlimit growthduring tiller and spikelet production.Treatments atthe start ofstem extensionprovideprotectionduring theperiod of tillerand spikeletmortality. Yieldresponses aremostly due toincreased grain numbers and tend tobe greater than responses to treatmentduring booting (GS45–49) or in earlyspring.Treatments aroundflag leaf emergencecan significantlyincrease grainnumber/m 2 probablyby increasinggrains/ear, byreducing spikeletmortality duringbooting.Treatment atbooting may extendcanopy duration,increase dry matter available for grainfilling and increase grain storagecapacity leading to higher thousandgrain weight (TGW). Later applications,towards the end of booting, have moreeffect through TGW.Winter six-row barley responds similarly to two-row barley with T1 sprays producing most yield effect through increased grain number/m 2 .The barley disease management guide 2009 10

Spring barley spray timingEar numberGrain number per earPotential grain sizeCanopy sizeGrain growthTiller productionSpikelet productionGreen canopy productionTiller lossSpikelet lossCanopy senescenceGrain fillingEmergenceGS12 GS22 GS25 GS31 GS39 GS49 GS59HarvestEarly spring T1 T2Early mildew controlmay be needed onvery susceptiblevarieties using aprotectant fungicide.The main timing formaximum tiller andspikelet survivalprovides protectionthrough to T2application becausespring varietiesdevelop at a fasterrate than winterones.This is the optimum time to protectcrops against late developingRhynchosporium, as well as leafspots, brown rust and net blotch.The aim is to maximise TGW andspecific weights and minimisescreenings. Growers who omit a T1spray may use an earlier timing(GS37-39).Disease management in spring barley aims to provide early protection of developingtillers and spikelets and then to protect grain development and filling. Timing isinfluenced by sowing date and disease risk of site and variety. Early-sown crops(eg January/February) may be treated like winter barley whereas crops sown latermay only require one or two sprays.Key points for both winter and spring barley:– Barley yields are usually limited by grain numbers per unit of ground area.– Foliar diseases can reduce tiller numbers.– Barley is less able than wheat to recover from early disease effects on tillering.– Disease management must start early to protect tillering and thedeveloping ears and spikelets.– Season-long protection maximises grain storage capacity.– For difficult to control diseases, eg Rhynchosporium, early fungicide applicationmay prevent epidemics developing.The barley disease management guide 2009 11

Foliar diseases –RhynchosporiumRhynchosporium secalisSymptomsInitially, pale grey water-soaked lesions appear,commonly at the leaf base close to the stem. Theselesions expand into pale, irregular patches with darkbrown margins across the foliage.ImportanceUntil 2004, Rhynchosporium was the most damagingdisease of barley in the UK, especially in the north andwest. More recently its importance has diminished dueto improved varietal resistance, although it can stillcause significant yield loss.UK survey data indicates that in 2005 farm crops had0.6% Rhynchosporium on leaf 2 at GS75, which equatesto a national yield loss worth £4.8 million (at £100/t)despite treatment.Life cycleSeedlinginfectionRainsplashcausesspreadof conidiaup plantConidia fromfungal stromatictissue are a primarysource of inoculumInfection causesblotch symptomsSeedinfectionOverwintersas myceliumin seed andon cropdebrisIn winter barley, symptoms can occur in autumn asrandom patches as a result of infection from rainsplash spores from crop debris, previous stubbleand volunteers. Widespread infection can occur inJanuary/February as a consequence of seed-borneinfection which initially develops inside the leavesand roots without symptoms showing.Symptom expression can be high at tillering stages ofgrowth in winter barley. Infection of upper leaves canalso occur in a wet summer. Spores on upper leavesmay spread to ears and affect seed.In spring barley, it is rare to see symptoms until aftertillering. Symptoms spread to the upper leaves duringa wet summer. Crops adjacent to affected winter barleycrops may become infected with rain splash sporesduring wet and windy weather.Risk factors– Cool, wet weather favours the disease, hence it ismost common in the north and west UK.Disease sources are seed, trash, volunteers andairborne spores.ControlVarieties– Select resistant varieties in high risk areas.– Avoid seed from affected crops.Cultural– Minimise barley trash and volunteers.– Avoid early sowing (December-February) of springvarieties.– Use clean seed stocks.– Avoid excessive N uptake.FungicidesIn autumn, control should only be considered if earlysymptoms cause extensive leaf damage.In early spring (March – GS30), if symptoms occur, afungicide application will help control disease until themain fungicide timing (GS31-32).At GS31 an effective triazole, in mixture with astrobilurin is a good foundation for diseasemanagement and in most crops will be the firsttreatment. For additional eradication, a morpholinecan be included in the mixture.Later protection of upper leaves is needed if weatheris wet between flag leaf emergence (GS39) and bootstage (GS49) – a mixture of chlorothalonil or boscalidwith a triazole should be considered.The barley disease management guide 2009 12

Foliar diseases –RamulariaRamularia collo-cygniSymptomsSmall brown ‘pepper spot’ lesions on the upper sideof leaves develop into dark-brown rectangular lesionswith yellow margins – easily mistaken for net blotch,particularly if lesions coalesce. Lesions develop moston the middle of leaves exposed to the sun and canbe seen on upper and lower surfaces. Symptoms alsooccur as small brown flecks on awns and stems.Ramularia symptoms can occur on dying leavesthroughout the season, but most commonly occuron upper leaves after ear emergence.ImportanceIncreasingly important in the north of the UK, butbecoming more common in the south. Spring varietiesare more affected than winter ones.Life cycleCarriedon seedInfectionspreadsto earRamularia is seed-borne, spreading to new leaveswithout visible symptoms. Symptoms usually appearwhen the crop is stressed. Then spores are releasedfollowing a period of leaf wetness. Although thesespores can cause secondary infections, they areimportant for seed infection.Risk factorsSeedlinginfectionAirbornespores fromcereal hostsLesions on deadlower leavesSpread toupper leavesConidiaDisease sources are seed, trash and airborne spores.– Stress, eg waterlogging, poor nutrition orphysiological stress.Under stress –symptoms onupper leavesControlVarietiesThe main economic loss is in spring malting barleywhere the varieties preferred by the market are notdisease resistant. Some spring varieties show betterresistance, eg Decanter, NFC Tipple and Appaloosa.Cultural– Prevent N stress/deficiency.FungicidesCurrent seed treatments have little effect ondisease development.Triazoles, eg prothioconazole and epoxiconazole,applied at the boot stage before symptoms appear,provide effective control and protect upper leaves.Using a triazole in mixture with boscalid orchlorothalonil achieves the best control.Strobilurins are no longer effective due tofungicide resistance.The barley disease management guide 2009 13

Foliar diseases – Net blotchPyrenophora teresSymptomsSymptoms can vary depending on source of infection:– seed: brown stripes spread from the base of leavesin seedlings and tillering plants.– spores from crop debris or neighbouring plants: long,brown lesions with a mottled or netted appearancedevelop.Leaf tissue surrounding lesions may be yellow and canoccur anywhere on the leaf. Lesions differ in size. Smalllesions appear as individual spots which can easily bemistaken for Ramularia. Diagnosis may requiremicroscopic examination.Symptoms can be extensive in winter, but affectedleaves die back and new leaves in spring can besymptom-free. The most serious symptoms usuallyoccur on upper leaves in summer on unprotectedsusceptible varieties.ImportanceNet blotch is a serious disease of barley causing largeyield losses when left uncontrolled. Infections fromtrash-borne inoculum pose the biggest threat to yield.UK survey data indicates that in 2005 farm crops hadan average infection of 0.85% on leaf 2 at GS75 whichequates to a national yield loss of £6.8 million (at £100/t)despite treatment.Life cycleStrong aircurrentsrelease conidiacausingreinfectionPrimary infection resultsfrom conidia and ascosporesOverwinters as seed-borne myceliumand as pseudothecia on crop debrisAt end of seasonpseudotheciadevelopRisk factorsDisease sources are seed, trash, volunteers andairborne spores.-- Mild, wet weather.– Second barley crops, especially after minimumtillage.ControlVarietiesHGCA Recommended Lists provide resistance ratingsfor winter barley varieties, but data is limited for springtypes. A resistant variety will reduce risk substantially.Cultural– Minimise previous crop debris.– Apply appropriate treatment on infected seed.– Manage N to avoid excessive concentrationsin plants.FungicidesSeed treatments protect against seed-borne inoculum.Seed testing can be used to assess the need for seedtreatment.Susceptible crops are at risk from late infections, sofungicides should be used to protect upper leaves.The triazole prothioconazole remains the most effective.Insensitivity to strobilurins is now widespread, but moststrobilurins show useful activity even where resistanceis widespread.The barley disease management guide 2009 14Splashdispersalof conidiaup plantTypical net likesymptoms occur

Foliar diseases – Brown rustPuccinia hordeiImportanceInfections threaten green leaf area and hence yield.Infections of the ear can also reduce quality.UK survey data indicate that between 2001 and 2005farm crops had an average of 0.3% on leaf 2 at GS75which equates to a national yield loss of £2.4 million ayear (at £100/t) despite treatment.Life cyclePustules of brown urediaerupt from the leafreleasing uredosporesMost rapid spreadoccurs at hightemperature latein the seasonTeliospores producebasidia and basidiosporesLate in the season blacktelia form on leaf surfaceControlVarietiesResistant varieties reduce disease risk, but varietalresistance can break down so any extensive outbreakwill require fungicide treatment.Cultural– Control volunteers to remove ‘green bridge’ inautumn and spring.– Manage N to avoid excessive concentrations in plants.FungicidesProtecting against infection is far more successfulthan eradicating established disease. Most strobilurinsand triazoles provide effective protection. Mixing amorpholine with one of these fungicide groups helpseradicate established disease. However, eradicationis difficult when ideal weather conditions for thedisease occur.SymptomsSmall brown spore pustules may form on leaves.Symptoms can occur at any time during the seasonand are usually scattered randomly. Lesions reducegreen leaf area.In winter barley, symptoms can occur in autumn andwinter if conditions are mild. However, affected leavesdie off and do not always lead to high disease incidencein spring.Favourable conditions (high temperatures and overnightdews) can occur in April–June leading to extensivesymptoms on the upper leaves in susceptible varieties.Slow disease developmentin spring – infection bywind-borne uredosporesOverwinters onvolunteersAecidial stagefound onalternate host(Ornithgalium)Brown rust can only survive on live leaf tissue, sooverwinters in crops and on volunteers. It spreads bymeans of airborne spores. Optimum conditions are dayswith high temperatures (15–22 o C) followed by overnightdews. Surface moisture on leaves is essential for sporegermination. Symptoms can occur in 5–6 days afterinfection at optimum temperatures.Risk factorsDisease sources are volunteers and airborne spores.– Humid, warm weather, especially in April to June.The barley disease management guide 2009 15

Foliar diseases – Yellow rustPuccinia striiformis f.sp. hordeiSymptomsIn autumn, yellow/brown spore pustules canoccasionally appear randomly distributed on leaves.They can easily be mistaken for brown rust. In spring,yellow pustules develop in distinctive lines. Withouttreatment, symptoms on susceptible varieties canbe extensive.ImportanceYellow rust is rare and has not been included innational surveys.Life cyclePustules eruptreleasinguredosporesEarly infection of plantsby wind-borne uredosporesSpringSummerDiseasespread bywinddispersalOverwinters onvolunteer plantsLate in the season blacktelia form on leavesAutumnTeliospores producebasidia andbasidiaspores (noalternate host known)Mild winter weather enables the disease to survive oncrops and volunteers.Cool (10–15ºC) temperatures, and prolonged periodswhen the leaves are wet, provide optimum conditions.Symptoms occur 7–14 days after infection. Hot, dryweather can stop disease development.Risk factors– Susceptible varieties.– Cool, wet weather in an early spring beforefungicides applied.ControlVarietiesEffective varietal resistance means yellow rust is rarenowadays.Cultural– Control volunteers to remove ‘green bridge’ inautumn and spring.– Manage N to avoid excessive concentrations in plants.FungicidesAs with brown rust, fungicides will protect againstyellow rust provided treatments are applied before thedisease becomes well established.Most strobilurins and triazoles are effective. Oncedisease is established, adding a morpholine to fungicidetreatments will help to eradicate the disease, buteffective eradication is a challenge when weatherconditions are ideal for the disease.The barley disease management guide 2009 16

Foliar diseases – Powdery mildewBlumeria graminis f.sp. hordeiSymptomsPowdery mildewproduces white fluffyfungal growth onleaves, stems andears. Individualpustules merge,under favourableconditions, to covermuch of the leaf andstem surfaces. Leafyellowing is associatedwith infection. Late inthe season, small blackfungal bodies developwithin pustules toproduce airbornespores.In winter barley, symptoms can occur in autumn orwinter under mild conditions.However, autumn infection can be reduced by winterfrosts, thus spring infection may not be severe.Spring barley is most affected at leaf emergence andtillering, but symptoms can develop as early as GS11(first leaf unfolded).ImportanceUK survey data indicate that between 2001 and 2005farm crops had an average of 0.3% on leaf 2 at GS75which equates to a national yield loss worth £2.4 milliona year (at £100/t) despite treatment.Life cycleMycelium develops on young plantsconidiophores release conidiaIn spring, conidia and ascosporesstart early infectionsThe fungus can only grow on living plants. It spreadsfrom winter crops to spring crops and to volunteerbarley via airborne spores. New pustules are producedin 5–14 days after infection.Risk factorsDisease sources are volunteers and airborne spores.Warm (15–22ºC), breezy conditions with short periodsof high humidity favour infection. Temperatures above25ºC and rain can inhibit the disease.ControlReinfection of leaf layersby airborne conidiaOverwinters as mycelium andcleistothecia on crop debris, autumnsown crops and volunteersCleistothecia developon lower leavesVarietiesThe risk of mildew can be substantially reduced bygrowing varieties with good mildew resistance (seeHGCA Recommended List).In spring barley, varieties with effective resistanceprovided by the ‘mlo’ gene should be grown wherepossible. Some mildew can develop on these varieties,particularly on seedlings during dry conditions. Howeverresistance has proved reliable and effective over thepast ten years.In some varieties adult plant resistance, which startsto become effective during stem extension, reducesinfection on upper leaves.Cultural– Manage N to avoid excessive concentrations in plants.– Control volunteers to remove ‘green bridge’ in theautumn and spring.FungicidesIn winter barley, control in autumn or winter is rarelywarranted.During rapid growth at tillering in the spring, powderymildew can cause yellowing and loss of tillers. Earlycontrol is therefore essential on susceptible varietiesto protect the crop from yield loss.Several fungicides (eg metrafenone, proquinazid,cyflufenamid) give effective protection when appliedbefore symptoms become extensive. Morpholines canprovide eradication and short-term control, but poorprotection. Mixing a protectant with a morpholine willeradicate and protect. Cyflufenamid provides bothshort-term knockdown and longer-term protection.Other fungicides (eg prothioconazole and cyprodinil)provide some protection, but activity is limited oncedisease is established. Strobilurins no longer controlmildew due to widespread resistance.The barley disease management guide 2009 17

Stem-base diseases – EyespotOculimacula acuformisO. yallundaeImportanceLosses due to true eyespot are less in barleythan in wheat. Other stem-base diseases seldomdamage yield.Life cycleConidia splash fromdebris to young plants.Ascospore infection ofautumn sown crops‘Eyespot’ lesionon stem baseLesions cause whiteheadsand sometimes lodgingControlVarietiesVarietal resistance to stem-base diseases is not assessedon barley.CulturalA two year break from cereals will substantially reduceeyespot risk, but a break of just one year will havelittle effect.FungicidesSeveral fungicides (eg prothioconazole, boscalid andepoxiconazole, and cyprodinil) are effective against bothRhynchosporium and eyespot when used at stemextension (GS31-32).Sexual stage on straw debrismay result in long distancespread of ascosporesRisk factorsDisease sources are trash and airborne spores. Earlysowing and high rainfall in spring increase eyespot risk.SymptomsTrue eyespot appears as brown marks at the stem baseon winter barley. These develop into typical ‘eye-shaped’lesions which weaken straw and impede water andnutrient uptake.Eyespot can be confused with sharp eyespot andFusarium.A risk forecast developed for winter wheat provides auseful indicator of risk for barley, since the same fungiare involved in both crops. However, the calculationshave not been tested for barley (see The wheat diseasemanagement guide, HGCA 2008).The barley disease management guide 2009 18

Ear diseases and mycotoxinsEar diseasesSpecific ear and grain diseases (eg Botrytis, Fusarium,Microdochium nivale, and sooty moulds includingAlternaria and Cladosporium) are encouraged bywet weather during flowering and grain filling.Foliar diseases (eg powdery mildew, Rhynchosporium,rusts, net blotch and Ramularia) can spread to the earsand awns. These diseases are best managed byprotecting upper leaves with a foliar fungicide.Seed-borne diseases (eg loose smut) can affect theear. Seed treatments control these diseases.For feed barley varieties, delaying the last fungicideuntil the ear is fully emerged, or applying an additionalear spray may help. However, for malting barley fewfungicides are approved for use after ear emergence.FusariumErgotClaviceps purpureaErgot can develop in the ear of any cereal crop, but it isless common in barley than open-flowered triticale orrye. Crops with secondary tillers are more susceptible.Ergot is common in weed grasses and field marginswhich should be checked for its presence. As ergot ishighly poisonous to man and animals, contaminatedgrain will be rejected. No fungicide is effectiveagainst ergot.ErgotIn the absenceof host crops,ergots which fallto the groundusually decayover a 12 monthperiod. Controlis helped byploughingbetween hostcrops and breakcrops combinedwith goodcontrol of cerealvolunteers andgrass weeds.Check crops just before harvest to decide if ergotinfested areas should be harvested separately.MycotoxinsLevels of mycotoxins (toxic chemicals produced byspecific fungi that infect crops) are much lower in theUK than in mainland Europe and rarely exceed currentEU limits.Fusarium species, that affect ear and grain, are themain mycotoxin producers in winter and spring barley.Mycotoxin risk, while lower than wheat, should beconsidered particularly if barley is commonly grownin rotation with maize with minimum tillage (seeGuidelines to minimise risk of fusarium mycotoxinsin cereals, HGCA (2007)).HGCA has also produced a Fusarium mycotoxin riskassessment tool to help identify wheat crops at risk(www.hgca.com/fusarium risk). This is a useful aidfor assessing barley risk too.Legal limits have been set for certain mycotoxins inbarley grain intended for human consumption (1250ppbDON (deoxynivalenol) and 100ppb zearalenone).EU guidelines apply for mycotoxin levels in barleyintended for animal feed (8,000ppb DON and 2,000ppbzearalenone – lower for certain classes of stock).Grain qualityEarly infections (pre-GS31) of foliar diseases canreduce photosynthetic area and restrict tilleringleading to lower yields with N content above the1.85% specified by many malting barley buyers.Smaller grains and increased screenings, whichmay lead to price penalty or rejection in both feedand malting markets, can result from foliar diseaseinfections after GS39.The barley disease management guide 2009 19

Virus diseases – Barley yellow dwarf virus (BYDV)Caused by an aphid-borne luteovirusInfected plants cannot becured, so methods toprevent infection and limitspread are necessary.SymptomsInfections cause leafyellowing and stunting,initially confined to singleplants scattered randomlyin a field but later developing into distinct circularpatches as secondary spread occurs.ImportanceBYDV is most damaging when young plants are infectedin autumn. Economic loss from a severe infection canmake the crop unprofitable.Life cycleIndividualplants andsmall patchesaffectedDirect tranfer fromgrass (wingless aphids)Aphids spreadvirus to otherplants in autumnand winterWinged aphids introducevirus to emerging cropsAffected plantsstunted and yellowPresent in late summer ingrasses and volunteersBYDV is transmitted by the grain aphid and the birdcherry aphid. Grain aphids feed on cereal crops andgrasses all year round. During late summer and autumn,winged aphids migrate between hosts, so this is whenthe disease is most likely to be introduced to crops.The LT50 (lethal temperature for 50% mortality) for grainaphid is -8°C, so they can survive through the winter insome years and even increase in numbers during mildspells. The bird cherry-oat aphid is more frostsusceptible,with an LT50 of 0.5°C, and tends to berestricted in cold winters to milder coastal areas.Risk factorsRisk in winter crops is greatly increased by:– early crop emergence.– mild winters– sowing after grassSpring-sown crops can also be infected, but substantialyield loss is rare.ControlThe only control option is to prevent infection andreduce its spread.CulturalGood stubble hygiene, or a gap of five weeks betweenploughing and sowing, will help prevent transmissionvia the ‘green bridge’ (ie aphids on grass weeds andvolunteers).Natural enemies include spiders, ground beetles andparasitoid wasps. Grass banks and uncultivated fieldmargins encourage natural enemies, but can alsoprovide a refuge for infective aphids. Therefore,the overall benefit may be unclear.ChemicalChemical control aims to prevent wingless secondand third generation aphids spreading disease withinthe crop.Development time for each generation depends ontemperature. It requires an accumulated sum of 170day-degrees above 3°C to produce a generation (the‘T-sum 170’). Treatments timed to coincide with theproduction of second generation aphids in a crop, ie atT-sum 170, are most cost-effective because they controlthe maximum number of aphids before any secondaryspread can occur. The T-sum 170 is calculated fromeither the time of emergence of the crop or from theend of the protection afforded by seed treatment (sixweeks from sowing).Treatments at T-sum 340 are sometimes justified onearly-emerged crops where winged aphid immigrationcontinued after the T-sum 170 spray was applied.Early emerged crops are most at risk of BYDV infection.Decisions on whether to treat crops emerging inSeptember must be made by the start of October. Thetreatment window is wider for later-emerging crops.The barley disease management guide 2009 20

Virus diseases – Soil-borne mosaic virusesBarley yellow mosaic virusBarley mild mosaic virusSymptomsAffected plants are stunted and pale. Leaves typicallyhave pale yellow streaks, especially in early spring,which are replaced by dark brown flecking and brownor purple leaf tips later in the season. Infections usuallyoccur in distinct patches that increase in size insuccessive years.ImportanceOnce present in the soil, it can persist in the absence ofa cereal crop for more than 25 years. Yield, within infectedpatches of a field, can be reduced by up to 50%. Aspatches are quite visible, it is easy to over-estimateaffected areas. However, overall yield can be reducedsubstantially as patches spread in successive crops.Life cycleRisk factors– Previous infection, that can persist for 25 years.– Soil movement, especially during cultivationsspreading within and between fields.ControlDisease cannot be controlled once plants are infected,so methods to prevent transmission and limit spreadare required.VarietiesWinter barley varieties, resistant to both mosaic viruses,are available (see HGCA Recommended List).CulturalCleaning cultivation equipment between fields willreduce the risk of the virus spreading.Polymyxa graminis formsintercellular plasmodiaand resting sporesVirus particles multiplyin the plant causing leafchlorosis and stuntingYellow stuntedplants in patchesin winter and springSymptomsfade astemperaturerisesRestingsporesin rootsThese virus diseases, very common in Britain inautumn-sown crops, are transmitted by the soil-bornePolymyxa graminis.Polymyxa graminis zoospores,carrying virus particules,infect root hairs in autumn/winterBYMV vector,Polymyxa graminislong-term survivalin soilThe barley disease management guide 2009 21

Assessing disease risk – The basisYield responses from some fungicide treatments can occur even where visibledisease is at very low levels. Once infection is established and visible, yield mayalready be affected and disease will be difficult to control. Avoiding yield lossrequires early decision making based on risk assessments. The likelihood ofinfection – ‘disease pressure’ – has to be balanced against ‘field resistance’,ie the ability of the crop to resist or avoid infection.Crop managementThe diagram below summarises the effect of various crop management practices ondisease risk. For example, a dense crop, early sown using min-till following barley wouldbe at very high risk of Rhynchosporium.Rhynchosporium Ramularia Net blotch Rusts Mildew EyespotDisease pressure must bebalanced against field resistanceEarly sownHigh N/dense crop➡ ➡➡ ➡➡ ➡ ➡ Diseasepressure=disease inoculum(this page)+weather and region(page 23)Fieldresistance=varieties(page 24)+crop management(this page)Min-till, iffollowing barley➡ ➡➡ ➡➡ ➡➡ ➡➡ ➡Key➡ ➡Increasedrisk➡➡Small increasein risk➡DecreasedriskDisease inoculumKey sources of inoculum differ for each disease. However, they generally includeseed, trash, soil, volunteers, and airborne spores and are primarily governed byfrequency of previous cropping, either in the same field or the vicinity.The barley disease management guide 2009 22

Assessing disease risk – Weather and regionHighModerateLowRhynchosporiumRamulariaNet blotch– Favoured by cool,wet conditionsRhynchosporium– Favoured by wetJune and JulyRamularia– Favoured bywet and humidconditions– Regional distributionvaries with seasonsNet blotchBrown rustMildewEyespot– Favoured by warmtemperatures(15–22 0 C)and dew formationBrown rust– Favoured by mild,humid conditionsMildew– Favoured byspring rainfallEyespotThe barley disease management guide 2009 23

Assessing disease risk – VarietiesHGCA Recommended List trialsassess disease susceptibility andyield across the UK each year. Theseprovide a clear guide of the strengthsand weaknesses of different varietiesand help in selection of varieties withresistance to diseases prevalent inspecific regions.Robust fungicide programmes areused in RL trials to maximise varietalpotential. Comparing treated anduntreated yields provides a usefulindication of total yield response tofungicides.Varieties with larger differencesbetween treated and untreated yieldwill usually need higher fungicideinputs to achieve their yield potential.In both winter and spring barley thesusceptibility of varieties to eachdisease is partly reflected in the yieldresponse to fungicides. Other factorsmay affect varietal yield response:– differing yield sensitivity todisease– diseases have differing effectson yield– fungicide effects not entirelylinked to control of visible disease,eg canopy ‘greening’ or growthregulatory effects.SpringWinterMaltingFeedMaltingtwo-rowFeedtwo-rowFeedsix-rowMildew Yellow Brown Rhyncho- Net Viruses* Yield response to fungicide treatment (t/ha)rust rust sporium blotch0.5 1.0 1.5 2.0Quench 9 4 4 8 – (6)Cropton 9 – 5 6 – (5)Concerto 9 – 6 4 – (7)Publican 8 3 5 8 – (6)NFC-Tipple 8 3 8 4 – (7)Forensic 5 – 5 5 – (7)Belgravia 9 (7) 6 7 – (6)Westminster 9 6 6 8 – (6)Cocktail 7 4 8 6 – (7)Oxbridge 7 5 6 7 – (6)Cellar 9 4 7 4 – (7)Optic 5 8 6 4 – (5)Decanter 9 8 5 6 – –Waggon 9 6 5 3 – (7)Sweeney 9 (4) 8 5 – (7)Scout 8 (2) 6 5 – (7)Jolika 9 (5) 4 5 – (7)Rebecca 6 4 6 8 – (4)Doyen 7 3 7 7 – (7)Riviera 8 6 4 5 – (5)Wintmalt 5 2 6 6 8 RFlagon 7 8 7 8 6 –Cassata 4 2 7 8 5 RPearl 6 6 6 7 5 –Retriever 5 8 6 8 7 RSaffron 3 7 7 6 8 –Accrue 6 7 7 8 8 –Suzuka 5 8 7 9 7 RCamion 5 7 5 6 8 –Carat 6 7 5 7 6 RVolume 5 6 5 8 8 RBronx 7 7 4 8 8 RPelican 7 5 8 8 6 RColibra 8 8 7 7 8 RBoost 7 8 4 8 8 RAmarena 8 5 8 8 7 –Sequel 5 7 5 8 7 ROn the 1 – 9 scales high figures indicate that a variety shows the character to a high degree (eg high resistance). ( ) = limited data*BYDV in spring varieties, BaYMV in winter varietiesSource: HGCA Recommended lists 2009/10The barley disease management guide 2009 24

Assessing disease risk – Variety diversificationMildew can spread between barley varieties that aresusceptible to the same race of the pathogen.The risk of severe and widespread infection may bereduced by:– Growing varieties with good resistance to mildew(as indicated by high resistance ratings on theHGCA Recommended List).– Diversifying the varieties grown so they are not allsusceptible to the same mildew race, using theVariety Diversification Scheme.Choosing varieties to grow together1. Select a first-choice variety and find itsDiversification Group (DG).2. Go to the selection matrix and find this DG under‘Chosen DG’ on the left-hand side of the table.3. Read across the table to find the risk of spreadof mildew for each companion DG.+ = Low risk of mildew spreadm = Intermediate risk of mildew spreadM = High risk of mildew spread4. Wherever possible choose combinations ofvarieties marked ‘+’. A combination marked ‘m’is a lower risk than one marked ‘M’.5. If there is a choice of varieties in a companionDG, give preference to those with higher resistanceratings (see 1-9 ratings on HGCA RecommendedList).Diversification group Winter varieties Spring varietiesDG1 Amarena Belgravia, Cellar, Cropton, Concerto,Decanter, Jolika, NFC Tipple, Publican,Quench, Riviera, Scout, Sweeney,Waggon, WestminsterDG3 (Mla3)DG4 (Mla13)DG10 (Mla6)Boost, Saffron, SequelDoyenCocktailDG14 (“Van”)Oxbridge, RebeccaDG0 Accrue, Bronx, Camion, Carat, Forensic, Optic(Mlra/Mlh/Mlg/Mla7/Cassata, Colibri, Flagon, Pearl,Mla12/MlAb/unknown) Pelican, Pict, Retriever, Suzuka,Volume, WintmaltVariety diversification scheme for barley mildew, 2009ChosenCompanion DGDG 1 3 4 10 14 01 + + + + + +3 + M m m m M4 + m M m m M10 + m m M m M14 + m m m M M0 + M M M M MSource: UK Cereal Pathogen Virulence Survey, funded by HGCA and DefraThe barley disease management guide 2009 25

Fungicide activity against major diseasesProtectionEradication★★★★ Excellent ★★★★★★★ Good ★★★Performance is scored according to whether spray is applied before (protectant) or after (eradicant) disease ★★ Moderate ★★becomes established. In high disease pressure situations, effective eradication will be difficult with any fungicide. ★ Low ★Chemical group Active ingredientActivity ratingRhynchosporium Mildew Brown rust Net blotch Ramularia Abiotic*Amidoxine cyflufenamid ★★★ ★★★Anilinopyrimidine cyprodinil ★★ ★★ ★ ★★ ★ ★ ★★Benzophenone metrafenone ★★★★ ★Chloronitrile chlorothalonil ★★ ★★★ ★★★★Imidazole prochloraz ★ ★Morpholine fenpropimorph ★ ★★ ★★ ★★ ★ ★★ ★fenpropidin ★ ★★ ★ ★★ ★ ★★ ★Quinolene quinoxyfen ★★Quinazolinone proquinazid ★★★ ★Spiroketalamine spiroxamine ★ ★★★ ★★ ★★★ ★★ ★★ ★Strobilurin azoxystrobin ★ ★★★ ★★ ★ ★★picoxystrobin ★★★ ★★ ★★★ ★★ ★★★ ★pyraclostrobin ★★★ ★★ ★★★ ★★ ★★★ ★★ ★★★trifloxystrobin ★ ★★ ★Strobilurin mixtures prothioconazole + fluoxastrobin ★★★★ ★★★ ★★ ★ ★★★ ★★ ★★★★ ★★★ ★★★ ★★★★kresoxim-methyl + epoxiconazole ★★ ★★ ★ ★ ★★★ ★★ ★★ ★★ ★★ ★★kresoxim-methyl + fenpropimorph ★ ★★ ★ ★★ ★ ★★ ★Triazole cyproconazole ★ ★ ★★★ ★★epoxiconazole ★★ ★★ ★ ★ ★★★ ★★ ★★ ★★ ★★ ★★flusilazole ★ ★★★ ★★ ★ ★metconazole ★ ★★★ ★★ ★ ★propiconazole ★★ ★★prothioconazole ★★★★ ★★★★ ★★★ ★★ ★★ ★★ ★★★★ ★★★ ★★★ ★★★★tebuconazole ★ ★★★ ★★Triazole +carboxamide epoxiconazole + boscalid ★★★ ★★ ★ ★ ★★★ ★★ ★★★ ★★ ★★★ ★★★★The barley disease management guide 2009 *Spots not associated with any known fungi, but which can be reduced by fungicide treatment.26

Active ingredients for barley disease controlNo Active ingredient Example products – single ai Example products – more than one ai1 azoxystrobin Amistar Amistar Opti, Priori Xtra2 boscalid only available in mixtures Chord, Deuce, Splice, Totem, Tracker, Venture3 chlorothalonil Bravo 500 Alto Elite, Amistar Opti, Cherokee, Credo,Midas, Zimbrail4 cyflufenamid Cyflamid5 cyproconazole Centaur Alto Elite, Cherokee, Furlong, Menara,Priori Xtra, Radius, Sphere6 cyprodinil Kayak, Unix Acanto Prima, Radius7 epoxiconazole Epic, Opus Capalo, Ceando, Chord, Deuce, Diamant,Eclipse, Envoy, Gemstone, Landmark, Mantra, Opera,Opus Team, Splice, Totem, Tracker, Venture8 fenpropidin Tern9 fenpropimorph Corbel Capalo, Colstar, Diamant, Eclipse, Ensign,Jenton, Mantra, Opus Team, Orka, Pluton10 fluoxastrobin only available in mixtures Fandango, Jaunt, Maestro11 flusilazole Capitan 25, Lyric, Genie 25, Sanction 25 Charisma, Colstar, Contrast, Harvestan, Medley,Midas, Pluton, Punch C12 kresoxim-methyl only available in mixtures Ensign, Landmark, Mantra13 metconazole Caramba, Caramba 90, Juventus, Sunorg Pro14 metrafenone Attenzo, Flexity Capalo, Ceando15 picoxystrobin Galileo Acanto Prima, Credo, Furlong, Zimbrail16 prochloraz Poraz Agate, Bumper P, Foil, Monkey17 propiconazole Bumper 250EC Bumper P, Cherokee, Menara18 proquinazid Justice, Talius19 prothioconazole Proline Cello, Fandango, Helix, Jaunt, Maestro,Mobius, Prosaro, Zephyr20 pyraclostrobin Comet 200, Comet, Flyer, Platoon, Tucana, Vivid Diamant, Envoy, Gemstone, Jenton, Opera21 quinoxyfen Apres, Fortress Orka22 spiroxamine Torch Extra Cello, Helix, Sage23 tebuconazole Folicur Agate, Cello, Monkey, Prosaro, Sage, Silvacur, Veto F24 trifloxystrobin Swift Jaunt, Mobius, Sphere, ZephyrProduct No Product NoAcanto Prima 6, 15Alto Elite 3, 5Agate 16, 23Amistar 1Amistar Opti 1, 3Apres 21Attenzo 14Bravo 500 3Bumper 250EC 17Bumper P 16, 17Capalo 7, 9, 14Capitan 25 11Caramba 13Caramba 90 13Ceando 7, 14Cello 19, 22, 23Centaur 5Charisma 11Chord 2,7Cherokee 3, 5, 17Colstar 9, 11Comet 20Comet 200 20Contrast 11Corbel 9Credo 3, 15Cyflamid 4Deuce 2, 7Diamant 7, 9, 20Eclipse 7, 9Ensign 9, 12Envoy 7, 20Epic 7Fandango 10, 19Flexity 14Flyer 20Foil 16Folicur 23Fortress 21Furlong 5, 15Galileo 15Gemstone 7, 20Genie 25 11Harvestan 11Helix 19, 22Jaunt 10, 19, 24Jenton 9, 20Justice 18Juventus 13Kayak 6Landmark 7, 12Lyric 11Maestro 10, 19Mantra 7, 9, 12Medley 11Menara 5, 17Midas 3, 11Mobius 19, 24Monkey 16, 23Opera 7, 20Opus 7Opus Team 7, 9Orka 9, 21Platoon 20Pluton 9, 11Priori Xtra 1, 5Proline 19Prosaro 19, 23Punch C 11Radius 5, 6Sage 22, 23Sanction 25 11Silvacur 23Sphere 5, 24Splice 2, 7Sunorg Pro 13Swift 24Talius 18Torch Extra 22Totem 2, 7Tracker 2, 7Tucana 20Unix 6Venture 2, 7Veto F 23Vivid 20Zephyr 19, 24Zimbrail 3, 15The barley disease management guide 2009 27

Foliar diseases – Fungicide doseDetermining appropriate doseFungicides are rigorously tested in HGCA-funded trials.Each year, a single spray is applied at a range of doseson varieties which are highly susceptible to each majordisease, and at sites where disease pressure is high.Disease levels are observed a few weeks later.Performance of individual active ingredients can beassessed by comparing dose-response curves. Theseshow average performance measured across a rangeof sites, seasons and leaf layers.Disease severity in untreated crops depends on localdisease pressure and varietal resistance. In treatedcrops, severity also depends on fungicide dose applied.The dose-response curveFungicide dose and marginFungicide spray cost increases with dose applied,while yield loss, to some degree, is proportional tothe amount of disease present. The figure belowplots fungicide dose against margin and identifieswhen the return from a higher dose would not beeconomically justified.How disease and variety affect appropriate doseDiffering disease pressure is a major reason for varyingappropriate doses between different crops. Clearly,higher disease pressure and disease susceptibilityjustify higher inputs.However, crop tolerance to disease (ie the yield lossfrom a given level of disease) and fungicideeffectiveness also modify the appropriate dose.To help in selecting the appropriate dose, see theFungicide performance tool on the HGCA website:www.hgca.com/diseasecontrolModerately resistantvariety under moderatedisease pressureThe appropriate dose depends on disease risk andpredicted yield loss and is defined as that point wheremargin is maximised.Below the appropriate dose, profit is seriously reducedby ineffective disease control.Maximising profit may mean accepting a small amountof disease in the crop despite treatment.Susceptible varietyunder high diseasepressureThe barley disease management guide 2009 28

Fungicide performance curvesRhynchosporiumNet blotchProtectionEradicationProtection – strobilurin activityProtection – other fungicide options16.025.06.06.014.05.55.512.020.05.05.0Rhynchosporium %10.08.06.04.0BravoOpusCometTrackerRhynchosporium %15.010.05.0BravoTrackerOpusCometNet blotch %4.54.03.53.02.5AmistarSwiftNet blotch %4.54.03.53.02.5Torch ExtraKayakOpus2.0FandangoProlineFandangoProline2.0GalileoComet2.0TrackerProlineFandango0.00.00 0.25 0.50 0.75 1.000.00.00 0.25 0.50 0.75 1.000.00 0.25 0.50 0.75 1.00Dose Dose Dose DoseYAll curves based on 2005–2007 aggregate dataThe barley disease management guide 2009 291.51.50.00 0.25 0.50 0.75 1.00

Fungicide performance curvesBrown rustMildewProtectionEradicationProtectionEradication9.09.04.57.58.08.04.07.07.07.03.56.56.06.03.0Talius2.5Fortress6.0Brown rust %5.04.03.0Torch ExtraProlineOpusBrown rust %5.04.03.0Torch ExtraProlineMildew %2.01.51.0CorbelCyflamidFlexityMildew %5.55.0MCorbel2.02.0GalileoOpusAmistarAmistar1.00.00 0.25 0.50 0.75 1.001.00.00 0.25 0.50 0.75Galileo1.000.00.00 0.25 0.50 0.75 1004.00.00 0.25 0.50 0.75 1.00Dose Dose Dose Dose0.5Torch Extra4.5Torch ExtraCyflamidAll curves based on 2005–2007 aggregate dataThe barley disease management guide 2009 30

Resistance to fungicides‘Fungicide resistance’ occurs as populations of a pathogen adapt to a fungicide. The specific mode of action of some modern fungicides (eg strobilurins) means the risk ofresistance occurring is greater than with older ones (eg chlorothalonil) with less specific activity.Resistance to strobilurins is widespread in barleypathogens. However, the effectiveness of fungicidesagainst different pathogens varies:– powdery mildew and Ramularia – strobilurins nolonger effective– net blotch – still some activity, especially frompyraclostrobin and picoxystrobin– Rhynchosporium – no resistance has been detectedand control remains effective– rusts – no resistance has been detected and controlremains effective.Triazole resistance results in reduced efficacy overseasons.– powdery mildew – the first disease to developtriazole resistance. Some of the newer triazolesprovide useful control.– Rhynchosporium – insensitivity is developing acrossmost of the UK, with Northern Ireland less affected.Higher doses are required to control less sensitivestrains.Prothioconazole continues to show useful activityagainst both powdery mildew and Rhynchosporium,but should be used in mixture with an effective partner.Quinoxyfen resistance may be reflected in poor activityagainst powdery mildew. Alternative fungicides includemetrafenone and proquinazid.Good resistance management is based on limiting exposure of target pathogen to fungicides– Practise good hygiene through disposal of crop debris and control of volunteers which may harbour disease.– Select varieties exhibiting a high degree of resistance to diseases known to be prevalent in your area.– Avoid growing large areas of any one variety, particularly in areas of high disease risk where the variety is knownto be susceptible.– Only use fungicides in situations where the risk or presence of disease warrants treatment.– Monitor crops regularly for disease and treat before infection becomes established.– Use the minimum effective fungicide dose.– Use effective fungicides with different modes of action in mixtures or as alternate sprays. Mixtures oferadicant fungicides with protectant materials offer the most flexibility as well as reducing resistance risk.– Avoid repeated applications of the same product or mode of action. Never exceed the maximumrecommended number of applications to each crop for any particular fungicide group.– When planning spray programmes, take into account any earlier use of fungicide groups as seed treatments.For more information on resistance management, see the Fungicide Resistance Action Group – UK(www.pesticides.gov.uk/rags.asp)The barley disease management guide 2009 31

Fungicide decision guide – Winter barleyWhile there are four key timings when a spray may be used, most winter barley crops are adequately protected by T1 and T2 sprays.Spray timing RationaleProduct choice and doseWinterRarely necessary unless extensive disease affectsoverwintering capability or in high risk snow rot crops.Use doses at 30–40%. If possible avoid triazoles to minimise resistance risk.Powdery mildew – fenpropimorph, spiroxamine, fenpropidinBrown rust – fenpropimorph, spiroxamine, fenpropidinRhynchosporium – cyprodinil, fenpropimorph, spiroxamine, fenpropidinNet blotch – cyprodinilSnow rot – epoxiconazoleT0GS23-30Early springUseful time to start control of established disease onsusceptible varieties. Yield responses vary, dependingon disease pressure.Use doses at 30–40%. If possible avoid triazoles to minimise resistance risk.Powdery mildew – fenpropimorph, spiroxamine, fenpropidinBrown rust – fenpropimorph, spiroxamine, fenpropidinRhynchosporium – cyprodinil, fenpropimorph, spiroxamine, fenpropidinNet blotch – cyprodinilT1GS30-32T2GS39-49GS59Main fungicide timing to control all foliar and stem-basediseases. 60% of response to fungicide is achievable atthis timing. Target will be to eradicate established diseaseand provide protection until the next timing.Good timing to protect upper leaves against brown rust,Ramularia and net blotch. Rhynchosporium risk will be lowerexcept in wet summer. Take care if using eradicant mildewfungicides, since they sometimes reduce green leaf area.40% of yield response comes here. Higher responses occurwhere late brown rust or Ramularia and where later harvests(ie north UK).Only use if no spray at GS39-49. Protection from ear disease(not malting barley). Fungicides choice is more limited.Use dose of 40–60% for triazole. For other fungicides in mixture use at 30–50% dose.Rhynchosporium – prothioconazole, epoxiconazole, boscalid (in mixture), strobilurin,cyprodinil, chlorothalonilNet blotch – triazole, strobilurin, cyprodinilPowdery mildew – fenpropimorph, spiroxamine, metrafenone, proquinazid,cyflufenamidEyespot – boscalid (in mixture), cyprodinil, prothioconazoleUse dose of main fungicide at 30–50%. Use other fungicides in mixture at 30–50%.Rhynchosporium – triazole, strobilurin, cyprodinilNet blotch – triazole, strobilurin, cyprodinilRamularia – prothioconazole, epoxiconazole, chlorothalonil, boscalidBrown rust – triazole and most strobilurinsFusarium – prothioconazole, epoxiconazole, and most strobilurinsThe barley disease management guide 2009 32

Fungicide decision guide – Spring barleyThere are three key timings at which a spray might be considered. Most spring barley crops are adequately protected by one or two sprays applied at T2 and/or T1.Spray timingT0GS12-22T1GS25-31T2GS39-49RationalePowdery mildew present on susceptible variety and timingcoincides with herbicide application.Good timing to protect against Rhynchosporium, brown rust,net blotch and mildew. 40% of yield response to fungicidescomes from treatments applied now.Best timing to protect upper leaves from disease. 60%of yield response to fungicides comes from treatmentsapplied now.Product choice and dosePowdery mildew – fenpropimorph, spiroxamine, metrafenone, proquinazidRhynchosporium – prothioconazole, epoxiconazole, boscalid (in mixture), strobilurin,cyprodinil, chlorothalonilNet blotch – triazole, strobilurin, cyprodinilPowdery mildew – fenpropimorph, spiroxamine, metrafenone, proquinazid, cyflamidEyespot – boscalid (in mixture), cyprodinil, prothioconazoleRhynchosporium – triazole, strobilurin, cyprodinilNet blotch – triazole, strobilurin, cyprodinilRamularia – prothioconazole, epoxiconazole, chlorothalonil, boscalid (in mixture)Brown rust – triazole and most strobilurinsThe barley disease management guide 2009 33

Further informationInformation on the efficacy of individual productsprovided in the ‘Fungicide performance tool’ on theHGCA website www.hgca.com – see ‘Online Resourcesand Tools’ – will be updated annually. Always consult theHGCA website for the latest version of these ‘doseresponsecurves’.HGCA guidesPest management in cereals and oilseed rape– a guide, HGCA (2003) G14The barley growth guide, HGCA (2006) G30HGCA Recommended Lists for cereals and oilseeds,HGCA (annual)Nozzle selection chart, HGCA (2007) P05Guidelines to minimise risk of fusarium mycotoxinsin cereals, HGCA (2007) G34The wheat disease management guide, HGCA (2008)G38The Encyclopaedia of Cereal Diseases, HGCA/BASF(2008) G41SAC Barley Disease Control Technical Note, SAC(2008) SAC BD1 (available from HGCA and SAC)HGCA Topic SheetsPosted free to levy payers on requestTopic Sheet 42 Rhynchosporium control programmes,HGCA (2001)Topic Sheet 57 Necrotic spots in barley: causes andcontrol, HGCA (2002)Topic Sheet 97 Ramularia leaf spot in barley, HGCA(2007)Topic Sheet 102 Managing mycotoxin risk in wheatintended for human food, HGCA (2008)HGCA Project ReportsAvailable at cost from HGCA366 Appropriate fungicide doses on winter barley:producing dose-response data for a decision guide(2005)368 Application timing of recent fungicides used inwinter barley disease control programmes (2005)392 Development and field testing of fungicide antiresistancestrategies, with particular reference tostrobilurin QoI group of fungicides (2006)408 Spray behaviour and efficacy of herbicides andfungicides applied to wheat at reduced volumes(2007)415 Investigation of Fusarium mycotoxins in UK barleyand oat production (2007)431 Impact and interactions of Ramularia collo-cygniand oxidative stress in barley (2008)436 Understanding fungicide mixtures to controlRhynchosporium in barley and minimise resistanceshifts (2008)The barley disease management guide 2009 34

HGCACaledonia House 223 Pentonville RoadLondon N1 9HYwww.hgca.comT 020 7520 3920 F 020 7520 3931publications@hgca.comDisclaimerHGCA has provided funding for the projects on whichthese guidelines are based but has not conducted theresearch or written the guidelines.While the authorshave worked on the best information available tothem, neither the HGCA nor the authors shall in anyevent be liable for any loss, damage or injuryhowsoever suffered directly or indirectly in relation tothe guidelines or the research on which it is based.Reference herein to trade names and proprietaryproducts without stating that they are protecteddoes not imply they may be regarded as unprotectedand thus free for general use. No endorsement ofnamed products is intended, nor is any criticismimplied of other alternative, but unnamed products.AcknowledgementsThis guide was funded by HGCA as a knowledgetransfer project and is based on research funded byDefra, HGCA and the Scottish Government. It waswritten by Jonathan Blake and Dr Neil Paveley, ADAS;Professor Bruce Fitt, Rothamsted Research; Dr SimonOxley and Dr Ian Bingham, SAC; and Dr ValerieCockerell, Scottish Agricultural Science Agency.HGCA is grateful to many experts who have commentedon draft versions of the guide, including: Dr Steve Ellis,Dr Peter Gladders, Dr David Lockley, Dr Mike Lole andJohn Spink, ADAS; Dr Louise Cooke and Dr PeterMercer, AFBINI; Dr Rosie Bryson, Barry McKeown,Will Reyer and Steve Waterhouse, BASF; Nigel Godley,Bayer; Bill Clark, Brooms Barn Research Station;Mike Ashworth, Du Pont; Dr Simon Edwards, HarperAdams University College; Dr Simon Hook, Dr ClareKelly, Prof Graham Jellis and Dr Jim McVittie, HGCA;David Stormonth, Interfarm UK; Dr Colin West, MAGB;Dr Rosemary Bayles, NIAB; Dr Bart Fraaije, RothamstedResearch; and David Ranner, Syngenta.Edited by Dr Clive Edwards, HGCA and Geoff Dodgson,Chamberlain.Design: Chamberlain.Photographs: ADAS, Dalton Seeds, SASAHGCA Guide 44 (G44)Electronic version can be downloaded at www.hgca.comPrinted on material containing at least 75% recycled content.© 2008 AHDB-HGCA263377