A generally hardy winter crop, barley is a popular cereal across Australia’s grain growing regions, with a variety of markets from stock feed through to malting and brewing where quality is paramount.

Barley loose smut has been detected in areas recently, which prompts the question, ‘what’s causing this and what can be done to manage it?’ 

About barley loose smut 

Caused by the pathogen Ustilago tritici (U. nuda), loose smut first appears at ear emergence, with masses of dark brown spores appearing in the place of healthy grains1. 

The spores are initially loosely held by a thick membrane that soon breaks releasing the spores onto other heads. Infected heads also have a fishy smell. Finally, all that remains is bare stalks where the spores once were.

A maximum tolerance of 0.1 gram of smut pieces per half litre, has been established as Grain Trade Australia commodity standard.

Agriculture Victoria states that using systemic seed treatments each year will effectively control this disease, though it also cautions that clean seed should be sourced following a loose smut outbreak. 

Success begins with seed selection

Certified seed remains the best option for crop establishment, which isn’t to say that retained seed isn’t an option (more on that later).

Seed breeders are tireless in their pursuit of varietal advances, which has delivered considerable gains in yield, grain quality, and even disease resistance to some extent. As is often the case though, advances in one area can come at the expense of others.

Selecting the right variety from a seed company for your farming situation can be challenging yet hugely rewarding exercise, often with peace of mind knowing that this seed is treated to the highest standards with a market standard fungicide.

Seed applied fungicides, like VIBRANCE®, while not invincible, are the first and best line of defense as it’s not always apparent that the source of the seed contains the pathogens responsible for smuts and bunts. Unfortunately, issues can still arise when seed applied fungicides are doing the heavy lifting.

The importance of using a quality fungicide is amplified when using retained seed. Particular attention should be paid to the cleanliness of the seed and achieving even and complete treatment coverage .

Which seed treatment is best?

The most effective means to control loose smut is using a fungicide seed treatment, which enables growers to keep the disease at low levels. While VIBRANCE® seed treatment is registered for the control of loose smut, no seed treatment gives complete control of loose smut. Many crops this season grown from seed treated with different fungicides, registered for loose smut control, have still developed the disease. 

The level of loose smut in barley has increased in recent years. This is largely associated with two factors: 

• Large scale use of newer varieties that are more susceptible than older varieties;
• Environmental conditions at flowering.

Tips for avoiding barley loose smut:

1. Use fresh, quality clean seed, free from chaff, dust or other crop debris (wherever possible).
2. Use a SDHI seed treatment at the top label rate for the disease: VIBRANCE® at 180 mL/100 kg seed
3. Coverage is king. Seed treatments must be applied evenly and to every seed, to ensure optimal efficacy. 

As with all farming, from the implements used to the fertilizer applied at sowing, it’s important that growers have their choice of seed treatment. VIBRANCE® fungicide is a market standard for cereal disease control with the broadest label for management of all common diseases, from smuts and bunts to rhizoctonia and pythium that impact seedlings at establishment.  

What to do in-crop

Monitoring and detection of barley loose smut is essential to prevent tainted grain from making its way into receival depots. If farmers intend on retaining seed for subsequent crops, care should be taken to exclude diseased areas from seed harvesting.

WA Department of Primary Industries and Regional Development (DPIRD) research scientist Kithsiri Jayasena said certified seed or testing are essential.2

"It is impossible to tell if your seed has the pathogen just by looking at the seed,” he said.

"One of the only ways to be sure your seed has very low levels of disease is to have it tested in a laboratory or to purchase certified seed."

A Western Australian study published by the Grains Research and Development Corporation, in June 2020, found that a well-timed foliar fungicide application can help manage seed infection.

Dr Jayasena said fungicide sprays during ear emergence reduced the loose smut embryo infection by 84 per cent in both 2017 and 2018, and 87 per cent during flowering stage in 2018, compared to the unprotected treatments.

While the trial at Kojaneerup South trial utilised a foliar application of the active ingredient tebuconazole, the GRDC cautioned against singular use of this active ingredient, noting the “exciting implications” for use of alternative modes of action to help manage the disease2. 

All foliar fungicide applications should be made in accordance with product labels and with consideration to withholding periods ahead of harvest.

Summary

A little time spent in paddocks now can help identify areas where loose smut is an issue, so that a winning plan can be formulated for next year’s crop. If retained seed is going to be a part of your plan, ensure that clean paddocks are identified and consider laboratory testing to confirm the cleanliness of the seed. In line with departmental advice, a quality systemic, seed applied fungicide such as VIBRANCE® should be used ahead of sowing next year.

 

Sources:

1 Bunts and smuts of cereals | Grain, pulses and cereal diseases | Plant diseases | Biosecurity | Agriculture Victoria

2 In-season fungicide options show potential to control barley Loose smut | Groundcover (grdc.com.au)

 

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