Controlling barley loose smut

Page last updated: Monday, 16 July 2018 - 9:42am

Please note: This content may be out of date and is currently under review.

Loose smut control is necessary to preserve grain yield as affected plants do not produce grain. Control is also necessary in order to maintain export opportunities, as some countries do not accept grain affected with this disease.

Trials in Western Australia and South Australia show that Hindmarsh, La Trobe and Granger barley are more susceptible to the seed borne disease loose smut. Trials demonstrate differences in the level of control from registered products. While all the products trialled signicantly reduced loose smut, some reduced a relatively high level of smut to nearly zero.

This factsheet has been prepared to provide an update on the effectiveness of seed dressings for the management of barley loose smut.

Key messages

  • Correct application of seed dressings registered to control loose smut is a critical step in controlling loose smut. Every seed needs to be adequately treated.
  • All seed dressings trialled in WA in 2013 significantly reduced levels of barley loose smut.
  • Trial data from 2013 indicates that the seed dressings EverGol® Prime, Vibrance® and Jockey® + Raxil® T can reduce loose smut to near zero levels in seed that was heavily infected.
  • All barley crops should be treated as the inoculum levels of loose smut are relatively high due to the popularity of La Trobe and Hindmarsh, which are more susceptible to loose smut than most other barley varieties.

Why control loose smut?

Loose smut reduces grain yield. Every tiller of infected plants produces a smutted head instead of grain, so if 5% of tillers are affected, a yield penalty of up to 5% can occur. Also, countries such as Pakistan have zero tolerance to loose smut contaminated grain.

If my seed is infected, is it better to replace it?

Not necessarily. In the past it was suggested that growers replace seed that had a 5% level of infection. However, replacing seed can be costly and poses the biosecurity risks of introducing new weeds or weeds with herbicide resistance. Instead, the data presented here demonstrates that even with heavily infected seed, the most effective fungicides can have close to 100% control of loose smut, so seed from those treatments should be suitable for sowing in the following season. Hence growers can retain their own seed and with the correct application of a seed dressing annually, keep the incidence of loose smut to minimal levels.

Which seed treatment should I use?

All registered seed treatments trialled are effective at reducing the amount of loose smut. Seed harvested from infected crops should be treated with one of the most effective fungicides to ensure the best control of disease transmission. Select a seed dressing that is registered for loose smut control and suitable for your level of risk of other diseases such as scald or powdery mildew. A list of registered fungicides is available from Seed dressing and in-furrow fungicides for cereals in WA. Insecticides are not discussed here but some seed treatments also have active ingredients that control storage pests or aphids during early growth.

Can I use in-furrow fungicides instead of seed dressing fungicides?

In-furrow fungicides are not registered for control of loose smut and numerous trials have shown they do not control smut.

Differences in variety resistance

Trials in 2014 and 2015 showed that Hindmarsh is the variety most susceptible to loose smut while La Trobe and Granger are moderately more likely to be affected by loose smut than the varieties Bass, Flinders, Gairdner and Scope CL. Seed of Hindmarsh, La Trobe and Granger should be treated with the seed dressings which provide best control.

2013 trial results

Table 1 The level of loose smut control (%) in DAFWA trials at Gibson and Wongan Hills in 2013 where the loose smut levels of untreated controls in 2013 were 4.1% and 2.5% respectively. Different letters indicate a statistically different level of effectiveness and all treatments were significantly better than nil. Vibrance data is not shown due to an application error at sowing. Prices current in 2013
Product name Rate applied/tonne seed Cost to treat 70kg/ha seed ($) Smut (% controlled) Gibson Smut (% controlled) Wongan Hills
EverGol® Prime 400mL 4.01 100% a 100% a
Jockey® + Raxil® T 3L + 1L 10.75 99% a 99% a
Raxil® T 1L 1.30 93% a 77% b
Vitaflo®-C 2.5L 4.20 93% b 99% a
Zorro® 4L 6.93 87% c 85% b
Rancona® C 1L 2.17 85% c 78% b
Jockey® 3L 9.45 76% d 61% c
Table 2 The level of loose smut control (%) Bayer trials at Regans Ford and Wubin in 2013 where the loose smut levels of untreated controls in 2013 were 4.0% and 2.8% respectively. Different letters indicate a statistically different level of effectiveness and all treatments were significantly better than nil. Prices current in 2013
Product name Rate applied/tonne seed Cost to treat 70kg/ha seed ($) Smut (% contolled) Regans Ford Smut (% contolled) Wubin
EverGol® Prime 400mL 4.01 100% a 97% a
Vibrance® 1.8L 3.74 97% a 86% a
Baytan® T 1L 3.05 75% b 64% b
Tri-Power® 4L 9.52 51% c 44% c

Correct seed application is important

Auger and applicator calibration are important as under and over treating seed is money wasted in addition to poor disease control (under-treated seed) or may reduce coleoptile lengths or cause other phytotoxic effects on the germinating seedling (over-treated seed). Three steps in the correct application of a seed dressing are:

  1. Calibrate your auger grain output: tonnes per hour = weight of a sample (kg) x 3.6 / time (seconds)
  2. Use a constant auger flow rate during the dressing operation
  3. Match the amount of seed dressing that is delivered to the auger flow rate

Example; if the auger is delivering grain at 20t/hr and the dressing rate is 4L/t seed, then 80L of dressing will need to be applied per hour or 1.333L/minute. Measure this to calibrate the applicator and adjust as required to achieve this rate.

Poor application of a seed dressing; many grains are untreated while some are over treated.
Poor application of a seed dressing; many grains are untreated while some are over treated

Company technotes are available on the internet. Other useful tips and a comparison of seed treatment applicators can be found in the Kondinin Group Research Report 'Seed dressing applicators'.

Will treated seed have no loose smut in it?

Loose smut is a numbers game. A seed treatment will greatly reduce the likelihood of plants producing an infected head, but even with 99.99% control of transmission occasional infected plants will occur. For example, if you have seed with an initial infection rate of 1% (40mg seed sown at 70kg/ha), 99.99% control means that you would still see two infected plants every hectare.

In terms of seed for the following season, loose smut spores are easily windborne, therefore spores from affected plants outside a crop can be blown into clean crops resulting in the harvest of infected seed. This is why treatment every year is necessary.

How can I assess my level of seed infection?

Department Diagnostic Laboratory Services (DDLS) can assess the level of seed infection by testing the embryo for presence of the loose smut fungus in seed.

Contact information

Blakely Paynter
+61 (0)8 9690 2115
+61 (0)8 9956 8504

Author

Andrea Hills

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