Barley Loose Smut

Main points

  • Barley loose smut infections are becoming more common in varieties such as Spartacus CL, LaTrobe, Rosalind and Hindmarsh.
  • Growers need to ensure that seed of these varieties have good coverage of an effective seed treatment fungicide prior to sowing in 2019.

Situation

Loose smut continues to be observed in many barley crops, particularly in Spartacus CL, LaTrobe, Rosalind and Hindmarsh as they are more susceptible than other varieties. Fathom, RGT Planet and Flinders are of least risk and the susceptibility of other varieties fall between these (Table 1). Loose smut is a seed-borne disease that becomes visible at flowering. Infection occurs following spores being released at flowering and spreading onto neighboring plants and crops. This results in the next year’s seed and crop being infected.

Infection incidence varies but in most cases losses will have been very low and economic loss minimal. Management decisions should bear in mind the potential risk and the costs of possible control options. Higher rates of registered fungicides will provide better control. Be aware that some products have unsatisfactory control; they will reduce smut but not as effectively as other products (Table 2). These include those relying on triadimenol and to a lesser extent tebuconazole and flutriafol.

Table 1. Average variety susceptibility to loose smut across three trials in Western Australia in 2018. Susceptibility is expressed relative to LaTrobe (100%); La Trobe plant infection was 9% (Gibson), 18% (South Perth 1) and 7% at South Perth 2.

Variety Smut levels relative to La Trobe (%)
Hindmarsh 102
LaTrobe 100
Spartacus CL 68
Bass 41
Rosalind 38
Maltstar 19
Compass 15
Granger 13
Fathom 11
Flinders 9
RGT Planet 5

Where seeds are sown and little rain follows soon after, it is likely that the efficacy of any treatment will be reduced as the fungicide will not be taken up through the roots in good time. This was illustrated by observations of incidence of loose smut in plots with and without treatment of Systiva® in seven NVT trials in South Australia in 2017. In these plots control varied from 70-95% from one trial site to another.

Management and seed treatment efficacy

Application of an effective seed treatment with good coverage to seed prior to sowing is very important for control. Seed treatment tests conducted by SARDI have shown that products containing just triadimenol provide only about 50% control of loose smut in Hindmarsh. Products containing flutriafol and tebuconazole or a low rate of Rancona Dimension (80 mL) allow noticeable infection to persist in crops. If using Vibrance or Rancona Dimension, the higher rates set for rhizoctonia control should be used. The most effective control is provided by products containing carboxin and the SDHI fungicides Vibrance and Evergol Energy.

Table 2. Efficacy of seed dressings registered for loose smut control in Hindmarsh in 2018 at three sites in Western Australia (common seed source used). Control is expressed as the percentage decrease in infected plants. The lowest rates registered for loose smut were applied.

 

Smut control (% reduction in plants)
Seed dressing Rate (L/t seed) Gibson Katanning Wongan Hills Average
EverGol® Energy 1.3 100 99 100 100
Vibrance® 1.8 95 96 98 96
Systiva® 1.5 96 93 100 96
Vitaflo C® 2.5 99 99 91 96
Raxil T® 1 70 79 74 74
Baytan T® 1 69 67 67 68
Rancona Dimension® 0.8 55 60 64 60
Untreated plant infection (%) 7 3 10

In South Australia growers are strongly advised to maintain use of seed treatments that provide control of powdery mildew as well as loose smut control. This may involve the use of a mix of products and is to reduce the level of mildew inoculum in the region and hence delay the emergence of fungicide resistance developing.

For more detailed information consult the SARDI Cereal Seed Treatments 2019 or the DPIRD equivalent

Further information on seed treatments

Save now, pay later – don’t skip cereal seed treatments

 

 

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