The HGCA wheat disease management guide 2011

Spring 2011 Introduction Contents

This updated Wheat disease management guide Seed-borne diseases Foliar and other diseases brings together the latest information on controlling Seed production and certification 3 Impact on yield formation 9 economically important wheat diseases. Foliar, stem- Seed sampling and testing 4 Infection and development 10 base, root and ear diseases are covered. The guide now Seed-borne diseases Spray timing 11 includes a section on ensuring good seed health – Bunt 5 Foliar diseases particularly relevant if you are home-saving seed. Microdochium seedling blight 5 Septoria tritici 12 Reliance on repeated fungicide sprays has increased Septoria seedling blight 5 Septoria nodorum 13 the pressure for development of fungicide resistance. Fusarium seedling blight 6 Yellow (stripe) rust 14 Some important mode of action groups have lost Ergot 6 Brown (leaf) rust 15 activity against major diseases. The guide describes Seedling blight, foot rot and leaf spot 6 Tan spot 16 how to account for varietal resistance when making Loose smut 6 Powdery mildew 17 spray decisions. Seed treatment Root diseases Most energy, greenhouse gas and economic costs are To treat or not to treat 7 Take-all 18 invested in crop establishment and nitrogen application, Product choice 8 Stem-base diseases in order to grow green canopy. It is important to prevent Eyespot 19 diseases destroying green area before it can re-pay the Ear diseases 20 investment during grain filling. Virus diseases 21 Assessing disease risk Naming of fungal diseases Most recent name Previous Commonly The basis 22 Latin names of pathogenic fungi are agreed by name called Varieties 23 international convention and these can change over time Mycosphaerella Septoria Septoria Weather and region 25 as new scientific evidence emerges (eg Septoria tritici graminicola tritici tritici is now Mycosphaerella graminicola ). However, in some Fungicides Stagonospora nodorum or Septoria nodorum Septoria cases the original scientific names have become widely New fungicides and resistance management 26 Phaeosphaeria nodorum nodorum used to describe the diseases they cause (eg Septoria Activity chart 27 tritici or Septoria leaf blotch) – distinguished from Latin Blumeria graminis Erysiphe graminis Powdery Active ingredients and products 28 names by not being in italics. In general the most widely mildew Foliar diseases used common names are given in this guide. Puccinia triticina Puccinia recondita Brown rust Fungicide dose 29 Fungicide performance curves Septoria tritici 30 Yellow rust, brown rust and mildew 31 The HGCA/BASF Encyclopaedia of Cereal Diseases (2008) illustrates and describes Decision guide symptoms and life cycles of common and less frequently found diseases. T0, T1, T2 32 T3 33 www.hgca.com/cde Further information 34

The HGCA wheat disease management guide 2011 2 Seed production and certification

Certified seed Farmers must declare any use of farm-saved seed to All seed bought and sold in the UK must be certified. the British Society of Plant Breeders (BSPB). Most Wheat quality standards (including varietal and species varieties are eligible for payment; the list is available at purity, germination, loose smut and number of pieces of www.bspb.co.uk. Payments must be made via a ergot) are prescribed in the Cereal Seed Regulations registered processor or directly to BSPB. Payments which are issued as statutory instruments by the UK for previously zero rated varieties will be refunded governments within the EU-wide framework. These immediately but declarations of these varieties are prescribe minimum quality standards but also allow subject to verification by BSPB. member countries to set stricter standards. Note, by law farm-saved seed cannot be sold, In the UK, ‘HVS’ (Higher Voluntary Standard) seed is shared or bartered. certified to higher standards for varietal and species purity, ergot contamination and loose smut. HVS seed Organic seed production is sold at a premium over EU standard seed. Organic certified seed must meet the same Seed can be certified at various stages as a variety is quality standards as commercialised. Certified seed of the second conventionally produced generation (C2) is the normal category for commercial seed. No conventional seed crop production. treatments should be used on organic certified or Certification and seed-borne disease farm-saved seed. All seed The Cereal Seed Regulations state: “Harmful organisms considered for organic which reduce the usefulness of the seed shall be at the production should be tested lowest possible level.” for seed-borne diseases. Standards exist for loose smut, currently rare in UK wheat, and ergot but there are none for seed-borne bunt or fungal seedling blights. Although not a requirement of certification, in practice most certified seed is treated; which diseases are controlled depends on the treatment.

Farm-saved seed Quality seed can be grown and processed on farm. The aim should be to meet at least the minimum certified seed standards.

The HGCA wheat disease management guide 2011 3 Seed sampling and testing By law, seed must be officially sampled and tested Germination testing Seed health testing before it can be certified. Sampling and testing are also Low germination, due to disease, sprouting, drying, – Never sow untreated seed without testing for seed- important for grain intended for farm-saved seed. mechanical or chemical damage, is a major cause of borne diseases, particularly bunt and Microdochium poor quality in UK seed. Where time is limited the seedling blight. Sampling tetrazolium test (TZ) is recommended. However, this – Test for ergot, loose smut, Septoria seedling blight – Sample grain before cleaning or drying; ideally with a does not detect low germination caused by disease and Fusarium graminearum if a problem is single or multi-chamber stick sampler. damage, but gives a good indication of potential suspected. – Wash equipment with water and detergent, before germination after treatment for seedling blights. and between lots, where there is a risk of bunt Regulatory standards and advisory thresholds contamination. – Keep grain intended for sowing separate from larger Disease Method Duration Results given as Regulatory S tandard grain bulks. A dvisory threshold – Only use seed from one field to reduce variability Bunt Wash 48 hours Spores per seed A Treat if 1 spore/ within a seed lot. Molecular test 48 hours Either over or under seed or more – Sub-divide seed lots over 30 tonnes into smaller lots. 1 spore/seed – Sample across the bulk, or trailer, at different depths Microdochium seedling Agar plate 7–10 days % infection A Treat if over 10% (see table below for number of samples required). blight Molecular 48 –72 hours Either over or under infection – Thoroughly mix all samples from a lot in a clean 10% infection bucket; divide to create a composite sample for testing. Septoria and Fusarium Agar plate 7–10 days % infection A Treat if over 10% seedling blights Primary samples required for given lot sizes Ergot Visual 500g 24 hours Number of pieces Maximum pieces: Lot size (tonnes) Primary samples required or 1000g in 500g or 1000g A S 3 pieces/500g Under 5* 10 search – minimum standard S 1 piece/1000g – HVS 5 10 Loose smut Embryo 48 hours % infection in Maximum infection: 10 20 extraction 1000 embryos (advisory) or A S 0.5% – minimum 20 –30 40 2000 embryos (certification) standard S 0.2 %–HVS *Seed treatment should only be used where necessary but with small seed lots it may be cheaper to treat than to Treat for seedling blights when sum of infection levels exceeds 10%. sample and test for seed-borne diseases. At present seedling blight caused by Cochliobolus sativus is a low risk in UK wheat.

The HGCA wheat disease management guide 2011 4 Seed-borne diseases

Bunt Tilletia tritici Microdochium seedling blight Septoria seedling blight Symptoms Microdochium nivale and majus Phaeosphaeria nodorum Symptoms appear after ears emerge. Plants are often stunted and sometimes have yellow streaks along the flag leaf. Infected ears are dark grey-green with slightly gaping glumes. Bunt balls replace all grains and, if broken, release millions of black spores smelling of rotten fish. Symptoms Importance The most common symptom of a serious attack Bunt occurs at low levels in some seed stocks. is poor establishment. The fungus can also cause root Contaminated grain may cause rejection. rotting, brown foot rot, leaf blotch and, in combination Symptoms with Fusarium species, ear blight. The most common effect is poor plant establishment. Life cycle Symptoms are so similar to those of Microdochium Spores on the seed surface germinate with seeds. Importance seedling blight that only laboratory analysis can After invading shoots and growing points, the fungus In most years Microdochium seedling blight occurs on distinguish them. Septoria nodorum is more commonly grows within the plant until ear emergence when bunt wheat seed and is the most important cause of seedling associated with necrotic blotching of leaves and glumes. balls replace grain. The spores contaminate healthy blight in the UK. Sowing untreated seed with high levels grain during harvest, transport and storage. Spores of infection causes very poor crop establishment leading Importance can land on soil or spread by wind to neighbouring to yield loss. Effects of Septoria seedling blight are usually less fields. Soil-borne spores can invade seedlings very Life cycle severe than Microdochium seedling blight. However, at early in germination. Inoculum (spores) are found in soil and on infected seed. high levels crop establishment can be badly affected. Risk factors Spores, released when seedling blight or stem-base Life cycle Seed-borne infection: browning occurs, are splashed up the plant and While the disease can survive on plant debris, most ultimately infect the ear. infections result from seed-borne inoculum. – Seed repeatedly sown without a fungicide treatment. Risk factors Risk factors – Seedbed conditions leading to slow emergence. – Wet weather during flowering. – High seed infection levels. Soil-borne infection: – High level of seed infection. – Untreated seed sown into poor seedbeds. – Very short time between harvesting first wheat and – Untreated seed sown into poor seedbeds. – Cool, wet soils. sowing second wheat. – Late-sown crops. – Dry soil conditions between harvesting and sowing. The HGCA wheat disease management guide 2011 5 Seed-borne diseases Fusarium seedling blight spread by wind to open grass and cereal flowers nearby. Risk factors Rain splash or insects carry spores to other flowers, – Any factor that slows germination and emergence, Fusarium graminearum leading to further infection. eg poor seedbeds. Symptoms Control – Extended periods of warm, moist weather. Poor plant establishment is the most common effect No fungicide is effective against ergot. In the absence of together with root rotting, brown foot rot and ear blight. host crops, ergots decay over 12 months. Check weed Importance grasses and field margins for ergot. Consider ploughing Loose smut At present Fusarium graminearum is the only Fusarium between host crops and break crops. Control cereal Ustilago nuda f. sp. tritici species that causes significant seedling losses in the UK. volunteers and grass weeds. Symptoms Life cycle Risk factors The ear is usually completely Inoculum occurs mainly on crop debris, but can be seed- – Grass weeds, particularly black-grass. replaced by black fungal borne. Spores are splashed up the plant to infect ears. – Cool, wet conditions during flowering. spores. Sometimes ears are partly affected. Spores are Risk factors – Prolonged flowering periods. released as soon as the ear – High levels of seed infection. –Late tillering. emerges leaving a bare ear – Sowing untreated seed into poor seedbeds. rachis with total grain loss. – Maize in the rotation. Seedling blight, foot rot Blackened ears are so obvious that very low and leaf spot incidences appear severe. Ergot Cochliobolus sativus Importance Claviceps purpurea Symptoms Seed certification and resistant varieties have minimised Symptoms Early symptoms include brown roots and coleoptiles. seed-borne infection. A hard, purple-black sclerotium, up to 2cm long, replaces Infected plants with brown spotting on lower leaves Life cycle some grains in the ear. usually grow to maturity. Severe infections cause The fungus is present inside the embryo. As seed Importance stem-base rotting and poorly filled ears. germinates the fungus grows within the plant and infects the ear at an early stage. Eventually spikelets Yield is hardly affected but ergot is highly poisonous to Importance are replaced with masses of fungal spores which are man and animals, so contaminated grain will be rejected Cochliobolus sativus is traditionally a disease of hotter released at ear emergence. Spores spread by wind to or require cleaning. Standards for number of ergot pieces climates. Symptoms only occasionally occur in the UK. exist for certified seed. nearby open flowers and infect developing grain sites Life cycle on healthy plants. Life cycle The soil and seed-borne fungus survives on crop debris Risk factors At or near harvest, ergots fall to the ground, or are and grass weeds. It sometimes causes seedling blight. – Cool, moist conditions during flowering. spread with contaminated seed. They remain dormant More usually it infects roots but the plant survives. until the following summer, when they germinate and Splash-borne spores infect seed in ears. – Infected neighbouring crops. produce spores, encased in sticky ‘honeydew’. Spores – Seed repeatedly sown without treatment. The HGCA wheat disease management guide 2011 6 Seed treatment –To treat or not to treat

Certified seed Farm-saved seed

Germination test

85% plus 78 –84% Under 78%

Considering sowing Is heat damage untreated? present?

YES YES DO NOT NO NO USE FOR Test seed for bunt and Microdochium seedling blight. SEED Test for Septoria seedling blight if Septoria nodorum present in the growing crop.

Does bunt exceed 1 spore/seed? YES

NO

Do combined seedling diseases exceed 10%? YES

NO Treat seed with an appropriate Very low risk of seed-borne disease. product Consider sowing seed untreated. (see page 9)

High infection of Microdochium seedling blight (left)

The HGCA wheat disease management guide 2011 7 Seed treatment – Product choice

Seed-borne diseases Other diseases Active ingredient Product Bunt Seedling Loose Ergot Bunt Blue Take- Yellow Septoria Brown Virus vector blights smut soil-borne mould all rust tritici rust control carboxin, thiram Anchor Ch 3 3 3 3 clothianidin Deter By 3 clothianidin, prothioconazole Redigo Deter By 3 3 3 3 3 3 3 difenconazole, fludioxonil Celest Extra Sy 3 3 3 3 3 fludioxonil Beret Gold Sy 3 3 3 3 3 fludioxonil, flutriafol Beret Multi Sy 3 3 3 3 3 3 fludioxonil, tefluthrin Austral Plus Sy 3 3 3 3 3 fluquinconazole Galmano By 3 3 3 3 3 3 3 fluquinconazole Jockey Solo Bs 3 3 3 3 3 3 3 fluquinconazole, prochloraz Galmano Plus By 3 3 3 3 3 3 3 3 fluquinconazole, prochloraz Jockey Bs 3 3 3 3 3 3 3 3 fluquinconazole, prochloraz Epona Bs 3 3 3 3 3 3 3 fuberidazole, imidacloprid, Tripod Plus MA 3 triadimenol 3 3 3 3 3 3 3 3 3 fuberidazole, triadimenol Tripod MA 3 3 3 3 3 3 3 3 3 ipconazole Rancona 15ME Ch 3 3 3 3 3 3 prothioconazole Redigo By 3 3 3 3 3 3 prochloraz, triticonazole Kinto Bs 3 3 3 3 3 silthiofam Latitude Mo 3

Key to company: Bs=BASF By=Bayer CropScience Ch=Chemtura Mo=Monsanto MA=Makhteshim-Agan Sy=Syngenta

3 label recommendation 3 some known activity, but no label recommendation

The HGCA wheat disease management guide 2011 8 Foliar diseases – Impact on yield formation

Most foliar diseases accelerate senescence of the top three leaves and so reduce 7 yield. Fungicide sprays during canopy growth prevent green leaf area loss during Slow expansion Rapid expansion Senescence grain filling. T2 6 T3 Foliar diseases cause early senescence, loss Construction phase of GAI and yield Canopy growth: Canopy expansion accelerates in April/May as temperatures 5 rise and large upper leaves emerge. The maximum green area of leaves and Soil-borne, seed-borne, T1

stems (measured as green area index – GAI) is reached as ears emerge, just ) root and stem-base I 4 A diseases reduce canopy Crop protected before grain filling begins. G

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C Applying sprays during this critical phase – at T1 (GS32) and T2 (GS39) – limits 2 control foliar diseases disease progress and protects emerging upper leaves, so maximising H e a lt photosynthesis later. D h 1 is y e a s e Production phase d GS30 GS32 GS39 GS59 GS71 Grain filling: In this six to seven week period, up to 80% of yield comes from 0 photosynthesis. On bright days, yield typically increases by 0.2t/ha/day. In this Jan Feb Mar Apr May Jun Jul Aug Sep phase, stem reserve relocation accounts for 20% of grain filling. 25 A fungicide at full ear emergence may help prevent premature leaf loss.

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The HGCA wheat disease management guide 2011 9 Foliar diseases – Infection and development

Initial infection Latent periods, fungicide activity and spray timing Infection usually results from spores moving into the crop. When this occurs Example based on Septoria tritici depends on the disease. For example by spring, Septoria tritici is present on the lower leaves of most crops. GS32 GS33 GS39 GS59 Leaf 3 just emerged Leaf 2 just emerged Flag leaf emerged Ear emerged Disease development Infection is followed by a ‘latent period’ when the fungus grows within the leaf but Latent infection First spores arrive First spores arrive the leaf exhibits no symptoms. (no symptoms) Leaf 1 Leaf 1 The cycle of leaf emergence, infection, latent period and symptom expression applies (flag leaf) Latent infection First spores arrive Latent infection to all foliar diseases. The latent period varies considerably between pathogens and is (no symptoms) Leaf 2 (no symptoms) First lesion Leaf 2 affected by temperature. At higher temperatures, latent periods are shorter. Leaf 2 Septoria tritici has a very long latent period (14 –28 days). Many modern fungicides First lesion can control disease after a leaf becomes infected but only for about half of the Leaf 3 Leaf 3 Leaf 3 Leaf 3 latent period. In the summer, Septoria tritici may have a latent period of 14 days, but 10–14 days 10–14 days 10–14 days Severe lesions fungicides provide eradicant control for only about seven days. Although there may be no symptoms on a leaf, infection may be so far into the latent period that no fungicide at any dose will control the fungus.

Importance of spray timing and latent period Leaf 4 and below Leaf 3 infected but Leaf 3 may now be Symptoms now visible already showing disease still in latent showing symptoms – on leaves 2 and 3, not symptoms. Disease on period and controllable. disease not now controllable by ear Spore lands Fungus penetrates Fungus grows Symptoms appear these leaves cannot controllable on this leaf sprays. Ear sprays top on leaf leaf inside leaf on leaf now be controlled. Leaf 2 just infected. layer. up protectant activity on the flag leaf. Leaf 3 can be Leaf 2 infected but still protected. in latent period, so disease controllable by flag leaf sprays. Latent period Infection from within crops Fungal growth beyond As stems extend and upper leaves emerge, the crop tends to grow away from the Fungicides effective in this period chemical control disease. Newly emerged leaves always appear free from Septoria tritici between GS32 and GS39. However, the crucial final three leaves are at risk as soon as they No disease symptoms visible emerge. By this stage, most inoculum comes from within the crop and spore movement from other fields is much less important. Rusts and powdery mildew Latent periods can be as short as 4–5 days for mildew and brown rust. Strategies have very short latent periods and can be found before leaves have fully expanded. to manage these diseases depend largely on protecting leaves as they emerge. In the absence of fungicide use, the final severity of disease is determined by variety and weather.

The HGCA wheat disease management guide 2011 10 Foliar diseases – Spray timing Foliar treatments Effects of spray timing on disease control To ensure adequate protection of the key yield forming leaves, fungicide treatments The optimum T2 spray gives maximum disease should be targeted to leaf emergence, rather than growth stage. Full emergence of The optimum T1 spray gives maximum disease control on leaf 3, and provides control on the flag leaf and eradicates any latent leaf 3 usually coincides with GS32 but this can vary between crops. Very early some protection for leaf 2. infections on leaf 2 that have escaped earlier sprays. sowing can lead to leaf 3 emerging as late as GS33, but leaf 3 may emerge at GS31 in late-sown crops. Thus, leaf emergence is the best guide for decisions on spray T1 T2 timings. With practice, this can be assessed quickly in the field. Growth stages

provide a second best option. ) 100 % (

Flag leaf

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Spray window t

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The ‘spray window’ for effective disease control on a particular leaf layer is c 40 e relatively narrow. The optimum spray timing is when a leaf has just fully emerged. s a

e 20 s – Spraying too early, when the leaf is not fully emerged, results in insufficient spray i D 0 on the leaf and thus poor control.

– Spraying too late means the disease is already established and results in poor ) 100 % (

control, especially with protectant fungicides. l 80 o r t 60 n o c Main timings 40 Leaf 2 e s

T1 timing – Leaf 3 emerged (usually coincides with GS32, but can be as early as a

e 20 s GS31 or as late as GS33). i

D 0 T2 timing – Flag leaf emerged (GS39)

Applying both T1 and T2 sprays at optimal timings gives effective disease control on ) 100 % (

the top three leaves – those most important in grain filling. l 80 o r t

n 60 o c Additional timings 40 e s

T0 timing – Usually two to four weeks earlier than T1. a e 20 Leaf 3 s i

Instances where a T0 spray may be considered include: D 0 – to delay Septoria tritici development GS31 GS32 GS33 GS39 GS59 Time of spray application – where mildew, yellow or brown rusts are active Effects of spray timings on disease control – when eyespot requires earlier treatment. The figures above were produced from trials. Sprays were applied at frequent intervals T3 timing –- Ear spray across a range of growth stages. Each curve shows the level of control achieved on May be used to control ear diseases and 'top-up' foliar disease control on the flag each of the top three leaves for the spray timings from GS31 to GS59. The interval leaf on susceptible varieties under high disease pressure. between T1 and T2 is important. Disease control on upper leaves will be lost if the interval extends beyond three weeks, especially when diseases with short life cycles, eg rusts or powdery mildew, are active. The HGCA wheat disease management guide 2011 11 Foliar diseases – Septoria tritici Mycosphaerella graminicola Life cycle Risk factors – Susceptible varieties. sometimes known as leaf blotch Airborne spores disperse in autumn/winter from previous wheat stubbles. These ascospores infect leaves to – Early sowing. Symptoms produce leaf spots from mid-autumn onwards and then – Rainfall: high risk Septoria periods occur during In autumn and spread by rain splash and physical contact between ‘splashy’ or prolonged rain, especially in May and winter, brown oval leaves. early June. leaf spots (lesions) occur on older Spread of pycnidiospores up plants Mild winters and wet, windy conditions in early spring by contact and rain splash leaves which contain increase risk. the diagnostic small Pseudothecia and pycnidia In autumn and spring, develop within lesions black fruiting bodies crops infected by Control (pycnidia). Several airborne ascospores Varieties lesions may turn The HGCA Recommended List contains varieties with large areas of leaf resistance ratings from 5 to 8 so a fungicide treatment brown. In spring and perithecia pycnidia (wind blown) (rain splash) is likely to be necessary in most instances. However, summer, lesions are ascospores a lower dose is required for effective control on more usually rectangular resistant varieties. and confined by leaf Overwinters as mycelium, pycnidia veins. Leaf lesions and pseudothecia on crop debris, Cultural are often surrounded by areas of leaf yellowing or death. autumn-sown crops and volunteers Avoid very early sowing of susceptible varieties.

During rapid development, water-soaked lesions gradually Fungicides turning brown may be present. Heavy rainfall encourages rapid spore movement from Control relies on using robust rates of azole fungicides lower to upper leaves during stem extension. Optimum at T1 and T2, in mixture with a fungicide of a different Importance temperatures are 1 5–20ºC. mode of action; usually an SDHI (bixafen, isopyrazam or Septoria tritici is the most damaging foliar disease boscalid) and/or chlorothalonil. of UK wheat, causing significant yield loss every year. Symptoms appear after a latent period (1 4– 28 days after Infection occurs in all crops. Unusually dry weather infection); this period reduces as temperatures rise. Resistance to strobilurin products is widespread and they throughout May and June may reduce losses. Higher are unlikely to be effective. rainfall areas in the south and west are most at risk. Some systemic seed treatments (eg fluquinconazole) National survey data over the past ten years indicates may give limited early control. that crops had an average of 5.3% Septoria tritici on leaf 2 at GS75, despite treatment, representing an annual yield loss worth £49 million (at £100/t).

The HGCA wheat disease management guide 2011 12 Foliar diseases – Septoria nodorum Phaeosphaeria (Stagonospora) Importance Risk factors nodorum Although Septoria nodorum is widespread, it is now rare – Susceptible varieties. for severe attacks to occur; when they do it is usually sometimes known as leaf and glume blotch – High rainfall during and after ear emergence. associated with high rainfall at ear emergence (eg south- – South-west and coastal locations. Symptoms west Britain). Here yield losses in untreated crops may On leaves, symptoms exceed 50%. Control are mainly oval brown lesions with a small Life cycle Varieties yellowish halo. Pale The HGCA Recommended List contains varieties brown, rather than Leaves and ear infected by with resistance ratings from 4 to 9. Resistant varieties contact and rain splash black, pycnidia are preferred in high risk areas. distinguish Septoria In spring, crops also infected by Cultural nodorum from pycnidiospores and ascospores Ploughing or cultivation to bury crop residues after Septoria tritici. The harvest may provide some control. indistinct brown pycnidiospores ascospores pycnidia may be only Seed infection Fungicides visible when lesions T1 and T2 sprays applied to control other diseases are held up to the light. usually control Septoria nodorum on the leaves. When Overwinters on crop Under high disease debris, grass weeds and risk is high, a T3 protectant ear spray is important. volunteers pressure, leaf Seed infection causes damping symptoms can include off and early infection of plant small purplish-brown spots. The pathogen survives in crop residues, volunteers and wild grasses. It can be seed-borne. Airborne ascospores On ears, symptoms are typically purplish-brown blotches from wheat stubbles spread infection to newly-emerged on glumes. crops. Secondary spread occurs when pycnidiospores, produced within leaf spots, are dispersed by rain splash. Symptoms appear within 7–14 days. The disease can develop very rapidly in warm temperatures (2 0– 27ºC) with long periods ( 6–16 hours) of high humidity.

The HGCA wheat disease management guide 2011 13 Foliar diseases – Yellow (stripe) rust Puccinia striiformis Life cycle Risk factors Epidemics are associated with mild winters that enable – Large variation between years in epidemic risk. Symptoms the pathogen to overwinter in crops and volunteers. – Overwinter survival is critical. Groups of yellow Cold winters with severe frosts restrict its survival. pustules forming – Problems occur after mild winters and on susceptible stripes between Summer varieties. veins are the main Disease – Cold winters with several frosts below -5ºC reduce spread by symptoms. Under Pustules erupt wind survival. hot, dry conditions – releasing dispersal uredospores Late in the season black – New races continue to develop that overcome the or after fungicide telia form on leaves major gene resistance of some new varieties. use – pustules may be difficult to detect. Control In spring, small Varieties patches (foci) Varieties with resistance ratings of 7 and 8 on the of leaves with Early infection of plants Autumn HGCA Recommended List give effective control and by wind-borne uredospores scattered yellow may be less prone to sudden loss of resistance than Spring Teliospores produce pustules precede Overwinters on basidia and varieties with a rating of 9. The wheat yellow rust rapid spread volunteer plants basidiospores (no alternate host known) diversification scheme is designed to help growers throughout the field. choose combinations of varieties in such a way as to Ears can also be In early spring distinct foci may occur; secondary spread reduce the risk of crop loss due to disease spreading affected. is through airborne spores as well as leaf-to-leaf contact. from one variety to another. Cool (1 0–15ºC), damp weather, with overnight dew or Cultural Importance rain, provides optimum conditions for disease Control volunteers that provide a ‘green bridge’ between New races developed in 2009; as a result over 30% of development. harvest and emergence of new crops. the 2010 crop was rated 4 or less for yellow rust. Severe UK weather conditions are unlikely to limit development Fungicides epidemics can occur where large areas of susceptible in spring or early summer. Symptoms appear 7–14 days varieties are grown. In untreated susceptible varieties, Azole and most strobilurin products are very effective, after infection so leaf tips may show symptoms before some SHDIs also have good activity. yellow rust can reduce yields by over 50%. However, leaves fully emerge. Hot, dry weather with temperatures well-timed fungicide sprays are usually very effective so over 25°C limit development. Systemic seed treatments (eg fluquinconazole or annual losses are small. triadimenol) may delay epidemic development where Outbreaks often occur in coastal areas from Essex to risk is high. the Borders and central England.

The HGCA wheat disease management guide 2011 14 Foliar diseases – Brown (leaf) rust Puccinia triticina Life cycle Risk factors Brown rust overwinters in crops and on volunteers. It – Seasonal weather – the disease is normally most Symptoms spreads by means of airborne spores. Cold winters may active when June and July temperatures are high. Most commonly reduce its survival. (However, in 2007 above average spring seen as tiny temperatures led to unusually early epidemics.) orange-brown Most rapid spread Pustules of brown uredia occurs at high – High humidity is necessary for epidemic progress. pustules scattered erupt from the leaf temperature, late in the season releasing uredospores Late in the season black – Susceptible varieties. over leaves. During telia form on leaf surface autumn and winter – Early sowing. few pustules, – New races continue to develop that overcome the confined to older Teliospores produce major gene resistance of some new varieties. leaves, may be basidia and basidiospores. Aecidial stage seen. While the found on alternate host (Ornithogalum) Control pustules can be Slow disease development but rare in UK in spring – infection by a similar colour wind-borne uredospores Varieties Overwinters on to those of yellow volunteers Resistant varieties provide good control. Varieties on the rust, they usually HGCA Recommended List have ratings from 3–9. These have a chlorotic Optimum conditions are days with high temperatures can change over time as new races of brown rust appear. halo. (1 5–22ºC) followed by overnight dews. Surface moisture Most current UK wheat varieties are very, or moderately, on leaves is essential for spore germination. Late in the season brown rust can become very severe susceptible, but some have good resistance. and cause leaf death. Leaf sheaths and ears are also Symptoms can appear in 5–6 days at optimum Cultural affected. Black spots occur on maturing crops when temperatures. The disease is active over a wider range Control volunteers that provide a ‘green bridge’ between pustules produce a second, teliospore stage. of temperature (7 –25ºC) than yellow rust. harvest and emergence of new crops. Susceptible varieties should not be sown early in September. Importance Fungicides There is large seasonal and geographic variation in Products containing azxoles, strobilurins and SDHIs are brown rust severity. The disease is more common in very effective. In a programme, treatment intervals southern and eastern England on susceptible varieties. should not exceed three to four weeks; they should be National survey data over the past ten years indicates substantially shorter under high disease pressure. farm crops had an average of 0.15% brown rust on Systemic seed treatments (eg fluquinconazole) may help leaf 2 at GS75, representing an annual yield loss worth delay epidemics developing where risk is high. However, £1.4 million (at £100/t). In 2007, a season when brown seed treatments are likely to provide less control of rust was prevalent, the cost was £11.2 million. brown rust than yellow rust.

The HGCA wheat disease management guide 2011 15 Foliar diseases –Tan spot Pyrenophora (Drechslera) Life cycle Control tritici-repentis Like Septoria nodorum, tan spot is trash-borne and Varieties favoured by minimum tillage. Ascospores produced on Resistance ratings are not currently available. Symptoms stubble, probably in spring, introduce the disease into Tan spot symptoms Cultural crops. Leaf lesions appear in 7 –14 days and produce are variable. Small Ploughing or cultivation to bury infected crop residues. splash-dispersed asexual spores. tan, or brown, flecks Fungicides develop into pale- Typical eye- Fungicidal control is difficult due to the short latent brown oval spots Rain splash shaped leaf moves spotting period. with dark centres. conidia symptoms up plant occur These lesions causing Strobilurin resistance in tan spot has been confirmed sometimes have re-infection elsewhere in Europe, and is likely to be present in a chlorotic halo. the UK. At end of season Numerous lesions pseudothecia can coalesce into develop large necrotic areas. Symptoms are very

similar to those of Overwinters as Primary infection results seed-borne Septoria nodorum from conidia and ascospores mycelium and diagnosis and as pseudothecia relies on spore on crop debris identification.

Importance High temperatures (20 –28ºC) and rain causing long Tan spot is still a minor UK disease, but appears to be periods of leaf wetness are ideal for tan spot becoming more common. Some severe cases have development. occurred in recent years. It is a major problem in Sweden, Denmark, Germany and France, and it is Risk factors perhaps surprising that tan spot is not more widespread in the UK. – Minimum and non-inversion tillage. – Long periods of wet weather from GS32 onwards.

The HGCA wheat disease management guide 2011 16 Foliar diseases – Powdery mildew Blumeria graminis Life cycle Risk factors Airborne conidia, produced on crops or volunteers, – Susceptible variety. Symptoms enable mildew to spread widely. Warm (15–22ºC), breezy – Sheltered fertile sites. White fluffy colonies of conditions with short periods of high humidity favour – High nitrogen. pustules often occur infection. New pustules are produced in on leaves from autumn 5–14 days. – Warm dry, but humid, weather. onwards. Re-infection of leaf layers On yellowing leaves, by airborne conidia Control pustules retain a Varieties distinctive ‘green Mycelium develops on young plants and conidiophores release conidia Cleistothecia develop Most recommended varieties show moderate resistance island’. Severe on lower leaves although Claire, Conqueror and Solstice are rated 4 on mildew can cover the HGCA Recommended List. almost the entire leaf surface and develop Cultural In spring, conidia and ascospores Avoid excessive nitrogen fertilisation. on ears and stems. start early infections Fungicides Later in the season, Overwinters as mycelium and pin-head sized, black cleistothecia on autumn-sown Fungicides with specific activity against mildew are crops and wheat volunteers fruiting bodies required where powdery mildew is a particular threat. Some treatments, applied at T0 or T1, provide long-term (cleistothecia) that Temperatures over 25ºC and rain can inhibit protection. Fungicide resistance is known to affect the produce sexual spores (ascospores) may be found on development. Sexually-produced spores provide a performance of various fungicide groups (eg strobilurins, the white colonies. mechanism for summer survival when leaf growth azoles, morpholines). has slowed. Importance Mildew can develop over a wide range of conditions but is sporadic, often affecting crops under stress. Although The HGCA/BASF Encyclopaedia very visible, it generally reduces yield much less than of Cereal Diseases other foliar diseases. Damaging attacks can occur (www.hgca.com/cde) provides anywhere in the UK, but yield losses rarely exceed 10%. information on disease identification. National survey data over the past ten years indicates CropMonitor that farm crops had an average of 0.2% mildew on leaf (www.cropmonitor.co.uk) 2 at GS75, representing an annual yield loss worth provides information on £1.9 million (at £100/t), despite treatment. disease prevalence and risk.

The HGCA wheat disease management guide 2011 17 Root diseases –Take-all Gaeumannomyces graminis Risk factors Fungicides var. tritici – High pH increases disease risk. Seed treatments, based on silthiofam and Severe attacks can also occur in acid patches. Poor fluquinconazole, can help to reduce the effects of Symptoms drainage, low nutrient status and particularly early take-all, particularly when used in conjunction with Take-all can infect plants sowing and light, puffy seedbeds, encourage the cultural control measures. Seed treatments do not alter at a low level without disease. the optimum sowing date, but can delay the take-all causing obvious epidemic, and reduce the yield penalty from sowing symptoms. However, Cereal volunteers and grass weeds, especially couch, second wheats early. moderate or severe in break crops will carry the disease through to Azoxystrobin or fluoxastrobin applied at T1 timing can infection reduces the following cereals. help suppress take-all. number of active roots over winter, which Control Seed treatment does not alter optimum sowing date restricts canopy growth. Cultural Infection of the crown Control relies largely on rotation and good soil (adventitious) roots in management and husbandry. Reducing the severity in Optimum sowing date for second wheats with or without treatment the spring and early summer restricts water and nutrient second and subsequent wheats is achieved by delaying 8.0 uptake, resulting in patches of whiteheads (bleached Silthiofam drilling compared with first wheats, and maintaining 7.8 ears) as grain fills. good soil structure and nutrient levels. ) 7.6 Untreated a h

/ 7.4 t

Varieties ( Importance 7. 2 d l

All varieties are susceptible to take-all but some are e 7. 0 Take-all is the major cause of ‘second wheat syndrome’ i Y 6.8 when yields of second wheat crops are frequently more tolerant in the presence of disease. The HGCA Recommended List yields for second wheats give 6.6 10–15% less than those of first wheats. 6.4 some guidance to choosing the most suitable varieties 1Oct 11Oct 21Oct 31Oct 10Nov 20Nov Take-all is usually most severe in the second to fourth for second and subsequent sowings. Yield responses Drilling date successive cereal crop, but generally yields recover to reflect take-all tolerance and eyespot resistance. some extent in continuous cereals – ‘take-all decline’. HGCA-funded trials, ADAS Rosemaund Varieties known to perform well as second wheats Take-all causes most damage on light soils where loss of include Duxford, Grafton, JB Diego, Ketchum, KWS Santiago and Oakley. active roots has a large effect on water and nutrient uptake.

Even on chalky boulder clay soils with high water See Take-all in winter wheat – holding capacity, losses of 10% are common in second management guidelines, and third wheat crops. On less well-bodied soils yield HGCA (2006) . losses can be much higher, so it may be uneconomic to grow second or subsequent wheat crops. www.hgca.com/publications

The HGCA wheat disease management guide 2011 18 Stem-base diseases

Stem-base diseases can be difficult to distinguish, only indicator of risk. Risk is increased by ploughing, a Estimating your eyespot risk particularly early in the season when treatment preceding wheat or cereal crop in the rotation, heavy With funding from HGCA, SAC devised an eyespot decisions are made. Identification is necessary because soils, and early sowing. risk model, summarised below, to help winter wheat eyespot is much more important than sharp eyespot There is a strong weather influence on disease growers. (Rhizoctonia cerealis) and Fusarium foot rot. During stem development. Wet spring extension, lesions caused by Fusarium and sharp weather increases risk. Factor Level Risk eyespot are generally confined to the outer leaf sheath. points Control Some fungicides give incidental sharp eyespot control Sowing date Before 6 October 5 but specific treatment is difficult to justify. Varieties After 6 October 0 Eyespot-resistant varieties Eyespot infection Under 7% tillers infected 0 on the HGCA Recommended at GS31–32 Over 7% tillers infected 10 List include Battalion, Beluga, Mean rainfall (mm) Under 170mm 0 Eyespot Cassius, Cocoon, Grafton, in March/April/May Over 170mm 5 Tillage Minimum tillage 0 Oculimacula acuformis (R type) Istabraq, Humber, KWS Target and Stigg. Plough 10 Oculimacula yallundae (W type) Soil type* Light 0 Fungicides Mean spring rainfall Medium 1 Symptoms Good control is difficult to over 170mm Heavy 5 Eyespot affects the stem base of winter wheat from achieve and may be affected autumn onwards. Lesions appear as red-brown blotches. under 170mm by the type of eyespot Previous crop Non-cereal 0 Mixed R and W type eyespot infections occur in most present. Many treatments Other cereal 10 UK crops. Symptoms may disappear as leaf sheaths die only reduce severity. Wheat 15 off during spring growth, but can reappear later. Prothioconazole or boscalid (the latter * add a further 5 points for brash and limestone soils Importance in mix with epoxiconazole), control both eyespot and Use the table to estimate your total risk points. This approach gives you the flexibility to decide on the level Eyespot reduces yield and quality by restricting water Septoria tritici well – a useful option at T1. Higher of risk that you will accept. and nutrient uptake. Yield losses may be large, doses are usually required for eyespot control. Specific particularly in early-sown crops. Severe eyespot can eyespot treatments should be applied at GS30-31 if Interpreting your total risk points cause lodging from weakened stems. Even without high risk justifies early treatment. lodging, severe eyespot can reduce yield by 1 0–30%. Yield response to foliar disease control usually exceeds Threshold if you accept minimum risk response from eyespot treatment. However, delaying Threshold if you accept higher risk Risk factors treatment until GS32 – for better disease control on Eyespot development in crops is difficult to predict. The leaf 3 – may compromise eyespot control, especially Low risk High risk need for control can be based on estimating disease risk if disease levels are high on susceptible varieties. 0 20 29 40 using local experience of incidence and weather. The Some control may be achieved at GS37 if eyespot has Increasing need for treatment visible presence of eyespot at stem extension is not the not penetrated the stem base.

The HGCA wheat disease management guide 2011 19 Ear diseases Diseases can affect grain quality by Specific ear diseases Legislation imposes a limit for Control of ear diseases reducing grain filling, leading to low deoxynivalenol (DON) in grain for Sooty moulds are caused by a mixture Sprays applied after ear emergence: specific weights and shrivelled grain. human consumption of 1250 parts of fungi, mainly Cladosporium and – top-up protection for flag leaf and Infections of Fusarium and per billion. In most years few UK grain Alternaria species, which grow on leaf 2 against foliar disease Michrodochium species may result in samples have exceeded this limit. glume surfaces in wet weather or on mycotoxins. Sooty moulds, and similar – protect the newly-emerged ear against prematurely ripened ears. They cause Risk of mycotoxin formation can increase if: diseases, may affect grain appearance foliar diseases little yield loss but can discolour grain, causing rejection for milling. – maize preceded the wheat crop – protect against specific ear diseases which affects marketability, particularly for NB ploughing maize residues reduces – limit mycotoxin accumulation. milling. risk Foliar diseases that affect the ear Sprays applied around GS59 can help Fusarium ear (or head) blights are – wet weather occurred during flowering. maintain canopy size and prolong its Septoria nodorum is potentially the caused by a range of Fusarium species Fungicide treatment can help reduce ear duration by protecting leaf and ear most damaging to yield. In south-west and Microdochium nivale and blight and mycotoxin risk provided the green area against disease. For ear blight England, foliar and ear infections can Microdochium majus . In recent years, recommended rate is used as near to control, spray during anthesis (GS61-65). cause yield losses of up to 70%. there has been concern about the link infection time as possible. between ear blights and the formation The T3 ear spray should be considered Yellow rust , in severe cases, infects of mycotoxins. Seed-borne ear diseases where it is necessary to ‘top-up’ disease ears. Details of diseases such as bunt, ergot control on the flag leaf and/or to protect In UK wheat, the main mycotoxin- Brown rust can also affect ears. and smut can be found at pages 6 and 7. the ear from disease. If no T3 spray is producing species are Fusarium planned, it is important not to delay the Powdery mildew , although very obvious culmorum, Fusarium graminearum and T2 spray. Delaying the T2 spray to allow on ears, does not cause large yield Fusarium avenaceum which all produce part of the ear to emerge will lead to losses. similar symptoms. The presence of ear poorer foliar disease control on the blight is not a good indicator of likely critical flag leaf and leaf 2. mycotoxin risk in UK crops.

For the latest information on fusarium mycotoxins and the risk assessment, see: www.hgca.com/mycotoxins

Septoria Yellow rust Mildew Sooty Fusarium poae Fusarium Fusarium Fusarium nodorum moulds culmorum graminearum avenaceum The HGCA wheat disease management guide 2011 20 Virus diseases Barley yellow dwarf virus (BYDV) BYDV is transmitted by the grain aphid and the bird Treatments at T-sum 340 may be justified where aphids cherry aphid. Grain aphids fly into crops during late continue to fly after the T-sum 170 spray. summer and autumn, spreading disease. The LT50 (lethal Decisions on whether to treat crops emerging in Symptoms temperature for 50% mortality) for grain aphid is September must be made by the start of October. The In wheat, infections cause -8°C. The bird cherry-oat aphid is more frost-susceptible, treatment window is wider for later-emerging crops. leaf yellowing and stunting, with an LT50 of 0.5°C. initially confined to single plants scattered randomly Risk factors in a field. Distinct circular Soil-borne cereal mosaic virus – Early crop emergence. patches develop later as (SBCMV) secondary spread occurs. – Mild winters. – Sowing after grass. Soil-borne wheat mosaic virus (SBWMV) Importance Control BYDV is most damaging Control measures aim to prevent infection and reduce The viruses are transmitted by the soil-borne organism when young plants are spread. Polymyxa graminis and can remain viable in soil for at infected in autumn. least 15 years. The viruses are spread by any movement Cultural Economic loss from of soil infested with Polymyxa graminis containing Good stubble hygiene and an interval of five weeks a severe infection SBCMV or SBWMV particles. can make the crop between ploughing and sowing help prevent unprofitable. Substantial transmission via the ‘green bridge’ (ie aphids on Symptoms yield loss is rare in grass weeds and volunteers). Symptoms vary from pale green to prominent yellow streaks on leaves and leaf sheaths, accompanied spring-sown crops. Chemical by moderate to severe stunting. Infections usually Insecticidal seed treatments can provide four to six Life cycle occur in distinct patches that increase in size in weeks’ protection for early-sown crops in high risk areas. successive years. An aphicide spray can prevent wingless second and third generation aphids spreading disease within the crop. Importance Mosaic virus is present in the UK but symptoms are not Development time for each generation depends on commonly found. temperature. An accumulated sum of 170 day-degrees above 3°C is necessary to produce a generation (the Control ‘T-sum 170’). Treatments are timed to coincide with the Once land is infected by SBCMV or SBWMV, the production of second generation aphids in a crop, at only practicable means of control is to grow resistant T-sum 170. The T-sum 170 is calculated either following varieties. Claire and Hereward have been shown to emergence or the end of seed treatment protection. have resistance.

The HGCA wheat disease management guide 2011 21 Assessing disease risk –The basis Crop protection decisions need to be taken as upper leaves emerge, well before Disease inoculum visible disease develops on yield-forming leaves. To estimate the likelihood of Disease lesions on lower leaves are the most common source of spores to infect upper disease development, it is necessary to consider the balance between disease leaves emerging during stem extension. Hence, if a particular disease cannot be found pressure and the field resistance of the crop. during field walking then the risk is low and no treatment is needed. Inspect the crop again one or two weeks later. However, if disease is visible, even at small amounts on lower leaves, the potential risk is high. Whether disease develops subsequently on Disease pressure must be balanced against field resistance upper leaves depends on varietal resistance, crop management and weather.

Crop management The diagram below summarises the effect of various crop management practices on Disease Field pressure resistance disease risk. For example, the highest risk of rusts would occur with: = = disease inoculum crop management – a susceptible variety (this page) (this page) + + – established using min-till – which may allow infected volunteers to survive weather and region varieties (page 26) (page 24) – with high N uptake leading to a dense canopy.

Septoria Septoria Brown Yellow Powdery mildew tritici nodorum rust rust (in spring) · * Early sown · · ·

High N/ The severity of future disease depends on disease pressure (determined by the dense crop · · · · · · amount of disease inoculum and weather) and the variety’s genetic ability to resist · that pressure. Min-till after Disease forecasting is not very precise – it is sufficient to decide if risk of disease wheat · · · · development is nil, low, moderate or high. ·

A higher fungicide dose is needed when disease pressure is high and varietal Key *mildew tends to · · resistance is low. Conversely, a resistant variety facing low disease pressure may · proliferate in spring Increased Small increase Small decrease Decreased on late-sown crops risk

· risk · in risk not require any treatment. · in risk

The HGCA wheat disease management guide 2011 22 Assessing disease risk – Varieties Variety Mildew Yellow Brown Septoria Septoria Eyespot Fusarium Yield response to fungicide treatment (t/ha) HGCA Recommended List trials rust rust nodorum tritici ear blight 0 0.5 1.0 1.5 2.0 2.5 3.0 1 assess disease susceptibility and m p Gallant 5 5 4 5 5 6 5 i u b o a yield across the UK each year. r n Solstice 4 4 4 5 5 5 6 G These provide a clear guide of KWS Sterling 7 9 7 6 5 6 6 the strengths and weaknesses Ketchum 8 4 5 6 6 5 6 2

of different varieties and help p Panorama 7 9 4 6 6 5 7 u in selection of varieties with o r Kingdom 6 6 4 7 6 5 6 G resistance to diseases prevalent KWS Podium 6 6 7 [5] 5 5 7 m in specific regions. i b Cordiale 6 6 3 5 5 5 6 a Robust fungicide programmes n Battalion 8 6 8 7 5 7 6 are used in RL trials to maximise Einstein 6 6 5 6 5 6 6 varietal potential. Comparing Cocoon 7 8 8 [7] 6 7 7 treated and untreated yields Invicta 6 8 8 7 6 5 6 3

provides a useful indication of total p KWS Target 6 8 6 [8] 6 7 6 u o yield response to fungicides. r Tuxedo 6 9 7 [9] 7 6 6 G Robigus 6 2 6 7 6 5 6

Varieties with larger differences m i

b Warrior 8 9 9 7 7 6 6 between treated and untreated a yields will usually need higher n Scout 6 9 9 8 6 8 6 fungicide inputs to achieve their Claire 4 9 5 7 6 6 6 yield potential. Beluga 5 9 4 5 5 7 6 Gravitas 6 7 9 [7] 7 6 6

The susceptibility of varieties to 4 Denman 6 7 5 [7] 6 6 6 p

each disease is partly reflected in u

o Viscount 7 5 9 [9] 5 6 6 the yield response to fungicides. r G

Glasgow 5 5 4 4 5 5 6 t

Other factors may affect varietal f

o Cassius 7 9 8 8 5 7 6 yield response: S Istabraq 5 9 4 7 5 7 7 – differing yield sensitivity to Alchemy 7 9 5 7 7 6 7 disease (tolerance) KWS Santiago 5 6 4 - 5 4 6 – diseases have differing effects Conqueror 4 5 5 [9] 4 5 6

4 Oakley 6 2 6 7 5 4 5 on yield p

u JB Diego 6 6 4 7 6 5 6 On the 1 – 9 scales o

– fungicide effects not entirely r Duxford 6 5 4 6 5 6 6 high figures indicate G linked to control of visible that a variety shows d

r Stigg 7 9 9 [7] 8 7 6 resistance to a high disease, eg canopy ‘greening’ a degree. H Grafton 7 8 3 6 6 7 5 or growth regulatory effects. [ ] = limited data Humber 5 8 5 5 5 7 6 Source: HGCA Recommended Lists Gladiator 7 9 5 6 5 5 5 2011/12 The HGCA wheat disease management guide 2011 23 Assessing disease risk – Varieties

Disease resistance Types of resistance Fungicide dose and variety Some varieties are highly resistant to disease and may Race non-specific resistance is effective against all 1500

not require fungicide treatment if disease pressure is t 1400 s

fungal races and is not subject to sudden failure. o

c 1300 low. Even under high disease pressure a moderate e

Therefore, the ratings provide a guide to the relative d

i 1200

c Resistant variety fungicide input may be sufficient. Other varieties are i g 1100

resistance of this type of variety that is unlikely to change n a u h f / very susceptible, requiring high fungicide input to reach 1000 Susceptible variety r £

quickly. Although control is not complete, it can be as e

v 900 their yield potential. o

effective as fungicides. This is the main type of n 800 i g r

Resistance for a given variety to a particular disease is resistance available against Septoria tritici. a 700 M rated on a 1 –9 scale (1=very susceptible; 9=immune) in 600 Race-specific resistance can provide complete 500 the HGCA Recommended Lists. 123 protection (rating 9) against rusts or powdery mildew. It is important to take disease resistance into account But new ‘races’ of the fungus may develop which can Total triazole dose in a programme Choice of a more disease-resistant variety can before deciding on an appropriate dose. overcome this form of resistance, leading to sudden loss significantly reduce the total fungicide input needed. of control. Understanding disease resistance and the effects of Fungicide dose and wheat price disease pressure can explain why disease levels on the Race-specific resistance to rusts and powdery mildew same variety may vary between fields and years. will no longer be effective if a virulent race of the fungus

emerges. When such a change occurs, the level of 1500 £160/t

High nitrogen uptake encourages rapid development of t

s 1400

varietal susceptibility then depends on its underlying o c rusts and powdery mildew. In such crops even 1300 e

race non-specific resistance. d i 1200 c moderately resistant varieties can suffer high levels i g a n 1100 £120/t h u f of disease. For example, Robigus and Consort were both rated 9 for /

£ r 1000 e

brown rust in the 2007/08 HGCA Recommended List . v

o 900 Early drilling (early September) puts crops at higher risk n i 800 However, a new race has evolved and therefore ratings g r to most diseases and moderately resistant varieties can a 700 £80/t have been reduced to 7 and 3 respectively in the M suffer high levels of disease. 600 2009/10 list. 500 123 RL Plus offers the easiest way to Total triazole dose in a programme explore thousands of data records and The optimum fungicide dose changes little with wheat sift out the variety best suited to your price. As the graph above illustrates, if wheat price chosen market, soil type, location, increases from £80 to £160/tonne then the optimum disease risk and sowing date. triazole dose increases by 20%. RL Plus is available online at Actual dose required varies less with grain price than www.hgca.com/varieties/rl-plus with disease pressure and variety resistance. Under moderate disease pressure the optimum dose of triazole for a disease-susceptible variety is more than that required for the more disease-resistant one. The HGCA wheat disease management guide 2011 24 Assessing disease risk – Weather and region

High

Moderate

Low

Septoria tritici Septoria nodorum Yellow rust – favoured by – favoured by high – overwinter mild and wet rainfall at ear survival critical to conditions emergence risk. Mild winters and susceptible cultivars increase risk

Yellow rust Septoria tritici Septoria nodorum

Brown rust Tan spot Powdery mildew – favoured by – favoured by wet – favoured by above average weather, high humid weather temperatures, temperatures usually most active and non-inversion in June/July tillage

Brown rust Tan spot Powdery mildew

The HGCA wheat disease management guide 2011 25 Fungicides – New fungicides and resistance management Succinate Dehydrogenase Inhibitors (SDHIs) Quinoxyfen-resistant isolates are now widespread in the mixtures with fungicides of a different mode of Since last season two new SDHIs have been approved UK. In 2009 and 2010, low levels of isolates resistant to action. Azole fungicides are available as single active for use, bixafen (in Aviator Xpro and other products) and metrafenone were detected in parts of Europe. substance products, but should not be used alone. isopyrazam (in Seguris). SDHIs inhibit a different enzyme Septoria nodorum For the major diseases, basing the programme on in the mitochondria of fungi to azoles. The new Strobilurin resistance has been reported in mainland azole + SDHI mixtures should provide some mutual generation have excellent efficacy on Septoria tritici , and Europe and may be affecting fungicide performance in the protection from the risk of resistance development a broad spectrum of foliar disease control. They are at UK. against both the components. medium/high risk of fungicide resistance so should always be used in mixtures (see below). Eyespot For Septoria tritici control, in most circumstances, Reduced sensitivity to prochloraz and cyprodinil has been adding chlorothalonil to azole or azole + SDHI Resistance known in parts of Europe for several years. There is no mixtures aids efficacy, reduces the risk of resistance Resistance occurs when a pathogen population becomes evidence of any sensitivity shift to cyprodinil in the UK. development, and should prolong their usefulness. so insensitive to a fungicide that its field performance is Some triazoles and boscalid achieve good control. However, if T2 sprays are delayed, the addition of impaired. Resistance can arise rapidly and completely so chlorothalonil may slightly reduce triazole or SDHI / that control is lost in a single step. Alternatively, if Reducing resistance risk: the role of mixtures triazole eradicant activity. Therefore, where infections resistance develops gradually, the pathogen population Azole and SDHI-based fungicides, are at risk of resistance are already established and full eradicant activity is becomes progressively less sensitive. Initially, field development. These fungicides should be used in a way needed, chlorothalonil should be omitted. performance may not be affected except under very high which slows resistance, to avoid future loss of efficacy. disease pressure and with susceptible varieties. For rust control, adding a strobilurin fungicide to an Using mixtures of fungicides with different modes of azole or azole + SDHI mixture may improve control Septoria tritici action and good efficacy, is key to reducing resistance and reduce the risk of resistance development. Only Sensitivity to triazoles has declined slowly since the mid- risk and achieving good control. two strobilurin sprays can be applied in any season. 90s, but efficacy of epoxiconazole and prothioconazole For this reason, SDHI fungicides are only available in remains good at label doses. Azole resistance is due to Good resistance management is based on limiting the level of exposure of the target pathogen to the fungicide various mutations and their frequency has changed quite rapidly in recent years. Resistance is widespread to both – Fungicide input is only one aspect of crop management and other control measures should always be used, MBC fungicides, since the mid 1980s, and strobilurin such as good hygiene through disposal of crop debris and control of volunteers which may harbour disease fungicides, since 2003. – Always aim to select varieties exhibiting a high degree of resistance to diseases known to be prevalent in your area, in addition to the main agronomic factors you desire Yellow and brown rust – Avoid growing large areas of any one variety, particularly in areas of high disease risk where the variety is known Although shifts in sensitivity to triazoles were reported in to be susceptible the 1990s, field performance has been maintained. No resistance has been found to morpholine or strobilurin – Only use fungicides in situations where the risk or presence of disease warrants treatment fungicides. – Use a dose that will give effective disease control and which is appropriate for the cultivar and disease pressure Powdery mildew – Make full use of effective fungicides with different modes of action in mixtures or as alternative sprays With rapid growth and many disease cycles each season, – Ensure that mixing partners are used at doses that give similar efficacy and persistence there is an inherently high resistance risk with this – Monitor crops regularly for disease and treat before the infection becomes well established disease. High levels of resistance to strobilurins in – Avoid repeated applications of the same product or mode of action and never exceed the maximum mildew mean these fungicides are ineffective. After an recommended number of applications initial shift, the sensitivity to morpholines and triazoles For more information on resistance management, see the Fungicide Resistance Action Group - UK has stabilised and they still provide partial control. (www.pesticides.gov.uk/rags.asp) The HGCA wheat disease management guide 2011 26 Fungicides – Activity chart

Chemical group Active ingredient Activity rating Choosing fungicides Eyespot Mildew Septoria Septoria Yellow rust Brown rust Ear blight # Fungicides should be nodorum tritici matched to the primary Amidoxine cyflufenamid HHHH disease risk, which Anilinopyrimidine cyprodinil HHHH HH HHH depends mainly on Benzophenone metrafenone HHH HHHH H variety, sowing date, Chloronitrile chlorothalonil H HH HHH HH Dithiocarbamate mancozeb H HH HH HH location and local Imidazole prochloraz HHH H HH HHH HH weather. Often fungicide MBC carbendazim HHHHHHHH mixtures with different thiophanate-methyl HH properties, from different Morpholine fenpropidin HHH H HH HH fungicide groups, are fenpropimorph HH H HH HHH most effective. Quinolene quinoxyfen HHH Fungicide resistance can Quinazolinone proquinazid HHHH Spiroketalamine spiroxamine HH HH HH dramatically affect Strobilurin (QoI) + azoxystrobin H HHH H HHH HHH fungicide performance, picoxystrobin HHHH H HHHH HHH so new information pyraclostrobin HHHHHH H HHHH HHHH should be taken into trifloxystrobin H HHH H HH HH account when planning Strobilurin mixtures dimoxystrobin + epoxiconazole HHHH HHH HHHH HHHH HHH fungicide programmes. fluoxastrobin + prothioconazole HHHH HH HHHH HHHH HHHH HHHH HHH kresoxim-methyl + epoxiconazole HH H HHHH HHHH HHHH HHHH To help select the kresoxim-methyl + fenpropimorph HH HHHH HH appropriate dose see the Triazole bromuconazole HHH H HH HH HH HH HHH Fungicide performance cyproconazole H HH HH HH HHHH HHH tool www.hgca.com/ difenoconazole H HHH HHH H HHH diseasecontrol epoxiconazole HH HH HHHH HHHH HHHH HHHH HH fluquinconazole HH HHHH HHH HHH HHH flusilazole HHH HH HHH HH HH HH Key flutriafol H HH HH HH HH HHHH Excellent metconazole HH HHH HHH HHH HHH HHH HHH Very good propiconazole HHHH HH HH HH HH Moderate prothioconazole HHHH HH HHHH HHHH HHH HH HHH H Poor tebuconazole HH HHH HH HHHH HHHH HHH tetraconazole HH HH HH HH HH # Ear blight caused by Fusarium culmorum or Fusarium triadimenol + tebuconazole HH HHHH HH HHHH HHHH HHH graminearum Triazole + carboxamide epoxiconazole + boscalid HHHH HH HHHH HHHH HHHH HHHH + Performance against Septoria epoxiconazole + isopyrazam HH HHH HHHH HHHH HHHH HHHH nodorum may be reduced by recent resistance. prothioconazole + bixafen HHHH HHH HHHH HHHH HHH HHHH The HGCA wheat disease management guide 2011 27 Fungicides – Active ingredients and products No Active ingredient Example products – single ai Example products – more than one ai Product No Product No 1 azoxystrobin Amistar Amistar Opti, Priori Xtra Acanto Prima 9, 25 Jaunt 16, 29, 36 Agate 26, 33 Jazz 4 2 bixafen only available in mixtures Aviator 235 Xpro, Boogie Xpro, Skyway 285 Xpro, Sparticus Xpro, Variano Xpro Alto Elite 6, 8 Jenton 15, 30 3 boscalid only available in mixtures Tracker, Venture, Nebula, Enterprise Amistar 1 Justice 28 4 bromuconazole Jazz – Amistar Opti 1, 6 Kestrel 29, 33 Anode 27 Lyric 18 5 carbendazim Delsene 50 Flo Contrast, Harvesan, Punch C Apres 31 Mantra 12, 15, 21 6 chlorothalonil Bravo 500 Alto Elite, Amistar Opti, Cherokee, Credo, Guru, Midas, Pentangle, Prairie, Prospa, Attenzo 24 Medley 13, 18 Zimbrail Aviator 235 Xpro 2, 29 Menara 8, 27 7 cyflufenamid Cyflamid – Boogie Xpro 2, 29, 32 Midas 6, 18 Bravo 500 6 Mobius 29, 36 8 cyproconazole Centaur Alto Elite, Cherokee, Furlong, Menara, Priori Xtra, Radius, Sphere Brutus 12, 23 Nebula 3, 12, 30 9 cyprodinil Unix Acanto Prima, Radius Bumper P 26, 27 Opera 12, 30 Capalo 12, 15, 24 Opus 12 10 difenconazole Plover Caramba 23 Opus Team 12, 15 11 dimoxystrobin only available in mixtures Swing Gold Ceando 12, 24 Orka 15, 31 12 epoxiconazole Opus, Epic, Ignite Brutus, Capalo, Ceando, Diamant, Eclipse, Ennobe, Envoy, Enterprise, Gemstone, Cello 29, 32, 33 Pentangle 6, 33 Icarus, Mantra, Nebula, Opera, Opus Team, Seguris, Swing Gold, Tracker, Venture Centaur 8 Plover 10 Cercobin 34 Pluton 15, 18 13 famoxadone Charisma, Medley Charisma 13, 18 Pointer 19 14 fenpropidin Tern Eros Cherokee 6, 8, 27 Poraz 26 15 fenpropimorph Corbel Capalo, Colstar, Diamant, Eclipse, Ensign, Jenton, Mantra, Opus Team, Orka, Pluton Cogito 27, 33 Prairie 6, 27 Colstar 15, 18 Priori Xtra 1, 8 16 fluoxastrobin only available in mixtures Fandango, Firefly 155, Jaunt, Variano Xpro Comet 200 30 Proline 275 29 17 fluquinconazole Flamenco Foil Consul 19 Prosaro 29, 33 Contrast 5, 18 Prospa 6, 19 18 flusilazole Lyric, Sanction 25 Charisma, Colstar, Contrast, Harvesan, Medley, Midas, Pluton, Punch C Corbel 15 Punch C 5, 18 19 flutriafol Consul, Pointer Prospa Credo 6, 25 Quell Flo 22 20 isopyrazam only available in mixtures Seguris Cyflamid 7 Radius 8, 9 Delsene 50 Flo 5 Sage 32, 33 21 kresoxim-methyl only available in mixtures Ensign, Mantra Diamant 12, 15, 30 Sanction 25 18 22 mancozeb Quell Flo Guru Eclipse 12, 15 Seguris 12, 20 23 metconazole Caramba, Sunorg Pro Brutus, Icarus Ennobe 12, 26 Silvacur 33, 35 Ensign 15, 21 Skyway 285 Xpro 2, 29, 33 24 metrafenone Attenzo, Flexity Capalo, Ceando Enterprise 3, 12 Sparticus Xpro 2, 29, 33 25 picoxystrobin Galileo Acanto Prima, Credo, Furlong, Zimbrail Envoy 12, 30 Sphere 8, 36 26 prochloraz Poraz Agate, Bumper P, Ennobe, Foil, Vareon Epic 12 Sunorg Pro 23 Eros 14, 33 Swift SC 36 27 propiconazole Anode Bumper P, Cherokee, Cogito, Menara, Prairie Fandango 16, 29 Swing Gold 11, 12 28 proquinazid Justice, Talius Vareon Firefly 155 16, 29 Talius 28 Flamenco 17 Tern 14 29 prothioconazole Proline 275 Aviator 235 Xpro, Boogie Xpro, Cello, Fandango, Firefly 155, Helix, Jaunt, Kestrel, Flexity 24 Topsin 34 Mobius, Prosaro, Sparticus Xpro, Skyway 285 Xpro, Variano Xpro, Zephyr Foil 17, 26 Torch Extra 32 30 pyraclostrobin Comet 200, Vivid Diamant, Envoy, Gemstone, Jenton, Nebula, Opera Folicur 33 Tracker 3, 12 31 quinoxyfen Apres, Fortress Orka Fortress 31 Unix 9 Furlong 8, 25 Vareon 26, 28 32 spiroxamine Torch Extra Boogie Xpro, Cello, Helix, Sage Galileo 25 Variano Xpro 2, 16, 29 33 tebuconazole Folicur Agate, Cello, Cogito, Eros, Kestrel, Pentangle, Prosaro, Sage, Silvacur, Gemstone 12, 30 Venture 3, 12 Skyway 285 Xpro, Sparticus Xpro, Veto F Guru 6, 22 Veto F 33, 35 Harvesan 5, 18 Vivid 30 34 thiophanate-methyl Cercobin, Topsin - Helix 29, 32 Zephyr 29, 36 35 triadimenol only available in mixtures Silvacur, Veto F Icarus 12,23 Zimbrail 6, 25 36 trifloxystrobin Swift SC Jaunt, Mobius, Sphere, Zephyr Ignite 12 The HGCA wheat disease management guide 2011 28 Foliar diseases – Fungicide dose

Determining appropriate dose Fungicide dose and margin How disease and variety affect appropriate dose Fungicides are rigorously tested in HGCA-funded trials. Fungicide spray cost increases with dose applied, Differing disease pressure is a major reason for varying Each year, a single spray is applied at a range of doses while yield loss, to some degree, is proportional to appropriate doses between different crops. Clearly, on varieties which are highly susceptible to each major the amount of disease present. The figure below higher disease pressure and disease susceptibility disease, and at sites where disease pressure is high. plots fungicide dose against margin and identifies justify higher inputs. Disease levels are observed a few weeks’ later. when the return from a higher dose would not be However, crop tolerance to disease (ie yield loss economically justified. Performance of individual active ingredients can be from a given level of disease) and fungicide effectiveness assessed by comparing dose-response curves. These also modify the appropriate dose. 50 show average performance measured across a range To help select an appropriate dose, see the of sites, seasons and leaf layers. 45 HGCA website: www.hgca.com/diseasecontrol

40 )

Disease severity in untreated crops depends on local a h 35 / £

disease pressure and varietal resistance. In treated (

) Margin over 50 t s % crops, severity also depends on fungicide dose applied. ( 30 fungicide cost o 45 c e

s Moderately resistant e

a 25

d 40 e i variety under moderate s c i i 35 g disease pressure D 20 n )

u 30 f %

Appropriate ( r 15

The dose-response curve e dose e 25 v s o a

Appropriate 45 10 e 20 n s i i dose g D 5 r 15

40 a

M 10 35 0 5 30 0 0.25 0.5 0.75 1 ) 0

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s Fungicide dose a

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s The appropriate dose depends on disease risk and 50 i D 15 predicted yield loss and is defined as that point where 45 margin is maximised. 40 10 Susceptible variety

) 35 5 under high disease Below the appropriate dose, profit is seriously reduced % ( 30 pressure e

0 by ineffective disease control. s

a 25

Untreated 0.25 0.5 0.75 1 e s Maximising profit may mean accepting a small amount i 20 Appropriate D dose Fungicide dose ( 1 = label recommended dose) of disease in the crop despite treatment. 15 10 5 0 0 0.25 0.5 0.75 1 Fungicide dose

The HGCA wheat disease management guide 2011 29 Fungicide performance curves

Septoria tritici protection Protection v eradication Septoria tritici eradication ‘Protection’ curves show the activity of fungicides 16.0 23.0 when they are applied soon after the emergence of a leaf layer before much infection has occurred. ‘Eradication’ curves indicate fungicidal activity against Septoria tritici after infection has occurred, but before symptoms become visible. Performance of products on each leaf layer, and at each 12.0 18.0 site, was classified as protectant or eradicant based on timing of leaf emergence relative to spray application.

% %

i i

c c

i i t t

i i

r r t t

a 8.0 a 13.0 i i r r

o o t t Aviator Xpro*

p p e e S S Brutus Isopyrazam** Opus Proline/Proline 275 4.0 8.0 Seguris***

*Aviator Xpro tested contained 150g/l of prothioconazole and 75g/l of bixafen. Aviator235 Xpro as available in the UK contains 160g/l prothioconazole with 75g/l bixafen. **Only available in mixture

*** Seguris was tested as a formulated pro duct in 2010, and 0.0 3.0 as a tank mix in 2008 and 2009.

0 . 0 0 . 2 5 0 . 5 0 . 7 5 1.0 0.0 0 . 2 5 0 . 5 0 . 7 5 1 . 0

C

Dose Dose (1.0 = label recommended dose) T 2008-2010 data 2008-2010 data

The HGCA wheat disease management guide 2011 30

Fungicide performance curves

Yellow rust Brown rust Mildew

41.0 15.0 8.0

12.0

31.0 6.0

9.0 % %

t t %

s s

u u r r

w

21.0 e 4.0 n w

d

l o w i

l

l o r e

M

Y B 6.0

11.0 2.0

3.0

1.0 0.0 0.0 0 . 0 0 . 2 5 0 . 5 0 . 7 5 1.0 0 . 0 0 . 2 5 0 . 5 0 . 7 5 1 . 0 0.0 0 . 2 5 0 . 5 0 . 7 5 1 . 0 D o se D o s e D ose

2008-2009 data 2008-2009 data 2006-2009 data

Aviator Xpro Brutus Comet Cyflamid FireFly Flexity Isopyrazam Opus Proline Talius T ern Torch The HGCA wheat disease management guide 2011 31 Decision guide – T0, T1 and T2

Spray timing Rationale Product choice and dose

Treatment combined with PGR before T1 may be appropriate in high disease Rusts – triazoles, strobilurins T0 years on susceptible varieties. Mildew – cyflufenamid, fenpropidin, metrafenone, proquinazid, quinoxyfen, spiroxamine Eyespot – boscalid + epoxiconazole, cyprodinil, flusilazole, metrafenone, prochloraz, Any yellow rust found should be controlled immediately. Controlling brown prothioconazole rust, mildew and eyespot may be economic where disease risk is high and on Septoria tritici – chlorothalonil susceptible varieties. Treatment may slow early rust epidemic development and reduce disease pressure at T1 and T2. Check crops in early spring for yellow rust, brown rust, mildew and eyespot. Low doses – quarter to half label recommended dose – are appropriate. Timing for eyespot and brown rust control – 2 –3 weeks before T1 applications. For Septoria tritici control, sprays are largely for insurance. Chlorothalonil applied three weeks before T1 applications would be adequate.

Primarily aimed at controlling Septoria tritici on recently-emerged final leaf 3 Base spray on a triazole/chlorothalonil mixture, possibly with the addition of SDHIs. T1 and sometimes diseases on leaf 4. Varieties susceptible to Septoria tritici Use doses between half and three-quarters of label recommended dose to ensure Leaf 3 (rated 5 or less on the HGCA Recommended List) should be targeted as high eradicant control of Septoria tritici. The triazole choice and dose is particularly important. emerged priority. Check growth stage and leaf emergence carefully at this time. Septoria tritici – chlorothalonil, triazoles, SDHIs Spraying too early or too late will give poorer disease control. Sprays applied for Septoria tritici will normally also control rusts. Rusts – morpholines, spiroxamine, strobilurins, triazoles, SDHIs Mildew – cyflufenamid, cyprodinil, fenpropidin, metrafenone, morpholines, proquinazid, Eyespot risk should be assessed. quinoxyfen, spiroxamine, SDHIs Strobilurins add to disease control and increase yield due to greening effects. Eyespot – boscalid + epoxiconazole, cyprodinil, flusilazole, metrafenone, prochloraz, prothioconazole

This is the most important spray as yield responses to flag leaf sprays are Doses between half and full label recommended dose are usually appropriate. T2 consistently profitable. Higher triazole doses are needed on Septoria tritici susceptible varieties under high Flag leaf disease pressure. Lower doses are appropriate on disease-resistant varieties under low This spray is aimed at controlling disease on the top two leaves, which emerged disease pressure. contribute approximately 65% of yield. Apply when most flag leaves on main tillers have emerged. Use triazole/SDHI mixture to ensure good eradicant control of Septoria tritici and prolong green leaf area of the top two leaves. Add chlorothalonil on Septoria tritici Varieties prone to Septoria tritici (rated 5 or less on the HGCA Recommended susceptible varieties in protectant situations. List) should be targeted for treatment first as delaying flag leaf sprays will be costly. Spray timing is less critical on more resistant varieties. Septoria tritici – chlorothalonil, triazoles, SDHIs Rusts – morpholines, spiroxamine, strobilurins, triazoles, SDHIs Mildew – cyflufenamid, fenpropidin, metrafenone, morpholines, proquinazid, quinoxyfen, spiroxamine, SDHIs

The HGCA wheat disease management guide 2011 32 Decision guide – T3

Spray timing Rationale Product choice and dose

The ‘ear’ spray targets ear diseases, but also gives additional control of Choose a triazole-based product or mixture with specific activity against ear diseases. T3 disease on the top two leaves – important in high disease seasons and on This also provides broad-spectrum eradicant control on upper leaves. Consider adding Ear spray disease-prone varieties. On Septoria tritici susceptible varieties, ensure a strobilurin where grain filling is likely to be prolonged or where brown rust is a risk. triazole applied for ear diseases is also active against Septoria tritici. A quarter to a half label dose is appropriate for additional disease control. A minimum of half dose is necessary for Fusarium control. In disease-resistant varieties, an ear spray may not be necessary. Preferred active ingredients specifically for ear disease control: Brown rust, yellow rust and Septoria nodorum can be damaging if ears are affected. Septoria nodorum – azoxystrobin, dimoxystrobin, epoxiconazole, prothioconazole, pyraclostrobin, trifloxystrobin. Wet weather during flowering can lead to Fusarium ear blight and possibly mycotoxins and discoloured grain. Control of ear blight is difficult and Fusarium ear blight – epoxiconazole plus dimoxystrobin, metconazole, costly as high doses must be applied close to the infection period. prothioconazole, tebuconazole. Avoiding mycotoxins is more important for wheat intended for human Sooty moulds – azoxystrobin, dimoxystrobin, pyraclostrobin, tebuconazole. consumption. Growers should use the HGCA Fusarium risk assessment tool and treat accordingly. Sooty moulds, which result in discoloured grain, have little effect on yield but can be important in milling varieties.

For the latest information on fusarium mycotoxins and the risk assessment, see: www.hgca.com/mycotoxins

The HGCA wheat disease management guide 2011 33 Further information

HGCA publications and details of HGCA-funded projects are all HGCA Topic Sheets, Information Sheets and Project HGCA Project Reports available on the HGCA website – www.hgca.com Progress PR418 Controlling soil-borne cereal mosaic virus in the UK by HGCA guides PP15 Fungicide performance in oilseed rape, HGCA (2010) developing resistant wheat cultivars (2007) HGCA Recommended Lists for cereals and oilseeds, TS104 Managing fusarium mycotoxin risk in wheat – PR432 Understanding the basis of resistance to Fusarium HGCA (annual) changes for harvest 2009, HGCA (2009) head blight in UK winter wheat (2008) G34 Guidelines to minimise the risk of fusarium TS96 Options for low volume spraying of winter wheat, PR439 Fungicide doses in sequences and mixtures for winter mycotoxins in cereals, HGCA (2010) HGCA (2007) wheat (2008) P05 Nozzle selection chart, HGCA (2010) TS95 Foliar disease control in wheat, HGCA (2007) PR444 Appropriate Doses Network: up-to-date information on G41 The encyclopaedia of cereal diseases, HGCA/BASF TS80 Determining eyespot risk in winter wheat, fungicide performance for wheat growers (2008) (2008) HGCA (2004) PR445 Assessing take-all risk in second wheats using the G39 The wheat growth guide, HGCA (2008) TS73 Testing winter wheat for seed-borne disease, Predicta B test (2008) G31 Take-all in winter wheat – management guidelines, HCGA (2003) PR456 Towards a sustainable whole-farm approach to the HGCA (2006) TS72 Sampling wheat seed for seed-borne disease, control of Ergot G14 Pest management in cereals and oilseeds, HGCA HGCA (2003) PR459 Monitoring risks of mycotoxin contamination caused (2003) TS56 Managing ergot in crops, HGCA (2002) by fusarium head blight pathogens in winter wheat (2009) G44 The barley disease management guide, HGCA (2011) (latest version available at www.hgca.com/publications)

The HGCA wheat disease management guide 2011 34 Current projects Websites 3187 United Kingdom Cereal Pathogen Virulence Survey Information on the efficacy of individual products will be (UKCPVS) updated annually with a range of online resources. Always consult the HGCA website for the latest versions. 3453 Integrated strategy to prevent mycotoxin risks HGCA – www.hgca.com British Society of Plant Breeders – www.bspb.co.uk 3479 Study of Fusarium langsethiae infection of cereals – Fungicide performance tool Chemicals Regulation Directorate – 3480 Identification and characterisation of resistance to (www.hgca.com/diseasecontrol) www.pesticides.gov.uk the take-all fungus in wheat (PhD) – Fusarium mycotoxin risk assessment CropMonitor – www.cropmonitor.co.uk 3517 Improved tools to rationalise and support (www.hgca.com/mycotoxins) stewardship programmes for SDHI fungicides to Crop Protection Association – control cereal diseases in the UK – RL Plus (www.hgca.com/varieties/rl-plus) www.cropprotection.org.uk 3570 Cephalosporium leaf stripe – an emerging threat – The UK Cereal Pathogen Virulence Survey Food Standards Agency – www.food.gov.uk to wheat crops in short rotations – Variety diversification scheme for yellow rust Liaison – https://secure.fera.defra.gov.uk/liaison 3573 Improved modelling of fusarium to aid mycotoxin – The Encyclopaedia of Cereal Diseases Fungicide Resistance Action Committee (FRAC) – prediction in UK wheat (www.hgca.com/cde) www.frac.info 3625 Identification, prevalence and impacts of viral Fungicide Resistance Action Group (FRAG-UK) – diseases in UK winter wheat crops (PhD) www.pesticides.gov.uk/rags.asp 3713 Identification and characterisation of azole NIAB-TAG – www.niab.com sensitivity shifts in Irish and UK populations of Mycosphaerella graminicola sampled from HGCA SAC – www.sac.ac.uk/crops fungicide performance winter wheat trials Science and Advice for Scottish Agriculture – 3729 Development of novel methods for detecting and www.sasa.gov.uk quantifying viable inoculums of Oculimacula The Voluntary Initiative – www.voluntaryinitiative.org.uk yallundae and O. acuformis (PhD) 3730 Value of resistance genes for controlling Septoria tritici in high-yielding wheat varieties (PhD) 3734 New fungicide performance in winter wheat

The HGCA wheat disease management guide 2011 35 HGCA Stoneleigh Park HGCA Publications Warwickshire, CV8 2TL T 0845 245 0009 www.hgca.com E [email protected]

Disclaimer Acknowledgements While AHDB, operating through its HGCA division, This guide was funded by HGCA as a knowledge HGCA is grateful to many experts who have commented seeks to ensure that the information contained on draft versions of the guide, including: within this document is accurate at the time of transfer project and is based on research funded by printing no warranty is given in respect thereof and, HGCA and Defra. It was written by Dr Neil Paveley, Dr Denise Ginsberg, ADAS; Dr Peter Mercer and Dr to the maximum extent permitted by law the Jonathan Blake and Dr Peter Gladders, ADAS; and Valerie Louise Cooke, AFBI; Nigel Adam and Nigel Godley, Bayer Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury Cockerell, SASA. CropScience; Steve Waterhouse, BASF; Bill Clark, howsoever caused (including that caused by Broom’s Barn; Dr Penny Maplestone, BSPB; Malcolm negligence) or suffered directly or indirectly in Tomkins, Chemtura Europe Ltd; Reuben Morris, relation to information and opinions contained in or omitted from this document. Cropwise; David Roberts, Dow AgroSciences; Patrick Goldsworthy, Goldsworthy Associates; Dr Simon Reference herein to trade names and proprietary products without stating that they are protected Edwards, Harper Adams University College; David does not imply that they may be regarded as Stormonth, Interfarm; Steven Burgner, Dr Victoria Foster, unprotected and thus free for general use. No Professor Graham Jellis, Dr Clare Kelly, Dr Jim McVittie, endorsement of named products is intended, nor is any criticism implied of other alternative, but HGCA; Dr Rosemary Bayles and Dr Kerry Maguire, NIAB; unnamed products. Dr Oliver Macdonald, PSD; Dr Simon Oxley, SAC; Huw HGCA is the cereals and oilseeds division of the Phillips, Scottish Agronomy; David Ranner, Syngenta; Agriculture and Horticulture Development Board. Mark Taplin, independent agronomist; and David Houghton and Julian Hasler, farmers. Edited by Dr Clive Edwards, HGCA and Geoff Dodgson, Chamberlain. 2011 Updates: Pinstone Communications Ltd.

Electronic version can be downloaded at www.hgca.com Photographs: ADAS, Scottish Agricultural College, Dalton Seeds, SASA Printed on material containing at least 75% recycled content.

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HGCA Guide 38 (G38)