Cereal Disease Guide 2013
Note Number: AG1160
Published: February 2005
Updated: February 2013
Drs Grant Hollaway & Mark McLean, Cereal Pathologists
Variety selection and robust disease management plans are critical to minimising the impact of diseases in cereal crops. The Cereal Disease Guide provides information on disease management and the disease resistant ratings for cereal crops. The disease resistance rating tables are available by clicking the following links:
2012 in ReviewA late start in June was followed by average winter rains and a very dry and cool spring. The stubble borne diseases, yellow leaf spot in wheat and spot form of net blotch in barley, were common during the winter months, especially when susceptible varieties were sown into diseased stubble. Dry conditions during spring did not favour further development of these diseases and as a result they did not progress up the canopy.
There was limited carry over of cereal rusts on volunteers during summer and the dry spring slowed their development. Some stem rust was observed on volunteer wheat growing in the Mallee during August and in Yitpi crops late in the season. Stripe rust was wide spread during October, but in general was only of significance in the more susceptible varieties.
Crown rot caused whiteheads in wheat crops during 2012. It was wide spread and favoured by the dry spring.
2013 The Year Ahead
There will be reduced carry over of rust inoculum following the dry summer; but growers must still have a plan to manage cereal rusts in susceptible varieties. Rust can quickly build up if suitable conditions occur.
Stubble borne diseases, such as yellow leaf spot in wheat and scald in barley, will be important due to the reduced break down of stubble. Therefore, susceptible varieties should not be sown into infected stubbles.
Variety selection and robust disease management plans will be important for minimising the impact of disease on cereal crops during 2013.
Wheat: Foliar Diseases
Stripe, stem and leaf rust will be of less importance during 2013 than 2011 or 2012 due to the dry summer conditions that have reduced inoculum survival and carry over on the few volunteers that have survived. It is, however, still important that growers have a plan to manage these rusts, particularly stripe rust in susceptible varieties. Growers should aim to:
- remove volunteer cereals by late-March,
- avoid growing rust susceptible varieties,
- apply fungicides on seed or fertiliser prior to sowing, and
- monitor crops with a view to timely fungicide sprays if necessary.
Avoiding susceptible varieties in the cropping system will greatly reduce the pressure from rust diseases and the likelihood of yield loss. Rusts are not only easier to control in varieties with resistance, but they also reduce the carry over of inoculum from one season to the next and reduce the chance of resistance breakdown.
No new rust pathotypes of significance to Victoria were detected during 2012. Because rust can develop new pathotypes it is important to always consult a current disease guide before sowing each year.
Yellow leaf spot was common in many Mallee and northern Wimmera crops during 2012 when susceptible varieties were sown into infected stubble. Yellow leaf spot can be controlled by avoiding susceptible varieties and by not sowing susceptible varieties into infected stubbles. The pressure from yellow leaf spot will be greatly reduced if susceptible (S) and very susceptible varieties (VS) were replaced with those rated moderately susceptible (MS) or better. Complete resistance is not needed to achieve sustainable control of this disease.
Septoria tritici blotch was common in higher rainfall cropping regions during 2012, following a combination of wetter growing seasons, the cultivation of susceptible varieties and an increase in inoculum levels. This disease may be of concern during 2013, especially if we have an average or above average rainfall.
Septoria, a stubble borne disease, can be controlled by avoiding sowing wheat into wheat stubbles and where possible, avoiding the more susceptible varieties. Some seed and fertiliser applied fungicides can provide suppression of early infection. Foliar fungicides are effective against this disease when used early in the disease development.
Bunt and Smut
Seed treatments provide cheap and effective control of bunt and smut diseases. Seed should be treated every year with a fungicide. Without treatment bunt and smut can increase rapidly, resulting in unsaleable grain. Good product coverage of seed is essential for good control.
Note that fertiliser treatments do not control bunt and smuts, so additional seed treatments are required. Clean seed should be sourced if a seed lot is infected.
Barley: Foliar Diseases
Scald and spot form of net blotch were common diseases of barley during 2012, with net form of net blotch and loose smut also reported.
Scald was less common during 2012 than in 2010 or 2011, most likely due to the later start to the season and below average spring rainfall. However, scald inoculum is still present in many paddocks so prepare to manage this disease, especially if growing scald susceptible varieties and there is an early start to the season. Experience during 2010 and 2011 showed that foliar fungicides work best when applied early in the epidemic (that is soon after symptoms are first seen, usually around growth stage 31). As with all stubble borne diseases avoid sowing into infected stubble.
Spot form of net blotch was common in barley cops during 2012, especially in susceptible crops grown in paddocks with one or two year old stubble. DPIVic experiments in 2011 showed a 10% yield loss and decreased grain size.
In 2013, avoid sowing susceptible varieties into barley stubbles from 2012 and 2011 as they will likely provide a source of infection. Where disease does occur in susceptible varieties, foliar fungicides can be effective if applied mid season (stem elongation to flag emergence).
Net form of net blotch (NFNB) can be a severe disease (worse than spot form) where susceptible varieties are grown. NFNB was reported in Victorian susceptible during 2011 and 2012 which re-enforces the need to avoid growing susceptible varieties. South Australian strains of NFNB, not yet detected in Victoria, will make some varieties more susceptible.
In 2013, avoid growing susceptible varieties and sowing into infected stubbles. If needed, foliar fungicides can provide some disease suppression. Note that NFNB is also seed borne so do not source seed from heavily infected crops.
Leaf rust was of little importance during 2012. Rust carry over was reduced due to the drier summer and the dry spring conditions limited disease development.
Even though a dry 2012/13 summer will reduce leaf rust survival and carry over further, it is important to have a plan to manage this disease if favourable conditions occur as it can cause 20% yield loss in susceptible varieties. DPIVic experiments have shown that as this disease develops later in the season, foliar sprays provide best control when used between flag leaf and ear emergence.
Triticale disease reactions
The reaction of triticale varieties to foliar diseases and cereal cyst nematodes is shown below.
||Yellow leaf spot
|^ These lines may be mixed with more susceptible plants|
Root and Crown Diseases
Crown rot, which caused widespread white heads in northern Victoria was the most important root disease during 2012. In the western district there were also more reports of take-all than in recent years.
To identify the potential risk from root disease a PreDicta B soil test (contact your local agronomist) can be used prior to sowing. Test results can identify potential root disease issues before they affect crop yield.
Most cereal root and crown diseases (take-all, crown rot, cereal cyst and root lesion nematode) can be controlled with a one or two year break from susceptible hosts. It is important that break crops are kept free of grass weeds to be effective. For more information on root and crown diseases see the DPI Agricultural Note “Cereal Root Diseases” (AG 0562).
Interpreting Resistance Classifications
Below is an explanation of the resistance ratings used in this guide for foliar diseases, and how they should be interpreted.
R = Resistant, the disease will not multiply or cause any damage on this variety.
MR = Moderately Resistant, the disease may be visible and will multiply slightly, but will not cause significant loss.
MS = Moderately Susceptible, the disease may cause losses up to 15% or more in very severe cases.
S = Susceptible, the disease can be severe on this variety and losses of 15-50% can occur.
VS = Very Susceptible, this variety should not be grown in areas where a disease is likely to be a problem. Losses greater than 50% are possible, and the build up of inoculum will create problems for other growers.
Below is an explanation of the resistance ratings used in this guide for nematodes, and how they should be interpreted.
R = Resistant, nematode numbers will decrease when this variety is grown.
MR = Moderately Resistant, nematode numbers will slightly decrease when this variety is grown.
MS = Moderately Susceptible, nematode numbers will slightly increase when this variety is grown.
S = Susceptible, nematode numbers will increase greatly in the presence of this variety.
VS = Very Susceptible, a large increase in nematode numbers can occur when this variety is grown and this will cause problems to a following intolerant crop.
These classifications are only a guide, and yield losses will depend on the environment and seasonal conditions.
Further InformationDetailed information on each of the cereal diseases can be obtained in DPI Information Notes: www.dpi.vic.gov.au/graindiseases
Cereal Root Diseases – 2010 (AG 0562)
Wallwork, H (2000) Cereal Leaf and Stem Diseases
Wallwork, H (2000) Cereal Root and Crown Diseases
Wallwork, H (2011) Cereal Seed Treatments 2013
Contact/Services available from DPI
DPI Field Crops Pathology, Grains Innovation Park, 110 Natimuk Rd, Horsham 3400. Tel (03) 5362 2111, or the DPI Customer Service Centre 136 186
This Information Note (AG1160) was prepared with assistance from Frank Henry (DPI Horsham), Hugh Wallwork (SARDI) and the Australian Cereal Rust Control Program (Cobbitty). Last Updated: 4th February 2013.