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Clean up the smut

These days, most growers are interested in planting corn, then soybeans, then wheat. In terms of priority, barley rarely makes the 10, which is too bad, since incorporating a fourth or even fifth rotational crop has been proven to have significant benefits for the more popular “Big Three.”

One factor that may be holding barley back in its bid to recapture acres is the recent increase in frequency and severity of loose smut. Part of this increase can be attributed to having just the right environmental conditions for the disease’s spread, yet according to Peter Johnson, cereals specialist for the Ontario Agriculture Ministry, it could also be attributed to weakening genetics.

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For example, OAC Kawartha, which has been one of the best barleys to come out of the provincial system and has been Ontario’s No. 1 barley variety, was tremendously consistent up until it started to have these loose smut issues, Johnson says. “Suddenly, for the last three or four years, we’ve been getting all sorts of complaints.”

Loose smut causes total yield loss in the infected plant, so it’s little wonder growers watch it with concern. Infected heads release their spores prior to harvest to blow across the field and infect healthy heads (by attacking the embryo). The spores won’t affect the quality of those healthy heads at harvest, but if and when those seemingly healthy spore-carrying seeds are planted the next year — and provided there are no control measures used — the spores will germinate and systemically infect the new plant and create a new batch of spores.

Plus, since environment plays such an important role in the disease’s development, the spores could lie dormant for years without any visual symptoms.

Cereal breeders haven’t helped, it’s thought, because they’ve taken their eyes off smut tolerance in order to focus on answering the grower’s demand for more yield and better standability. As a result, the drive for improved disease tolerance and resistance has been overlooked.

This is where seed treatments provided some levelling of the playing field. For years, Vitaflo 280 (carbathiin + thiram) was the standard for control of loose smut in barley. Now, it is suggested that its efficacy has decreased at the same time as the anti-smut power of barley genetics has also declined.

“You need both (genetics and seed treatments) working in concert to get the level of control you’d like,” says Johnson. “In this case, we had a reasonable fungicide but without that genetic support, it just couldn’t carry the load.”

Now the picture is improving, with new fungicides that are ready to carry more of that load — up to 95 or 98 per cent control.

Two of those fungicides are Dividend XL RTA (difenoconazole + metalaxyl-M) from Syngenta, and Rancona Apex (ipconazole), from UAP Canada. According to Brodie Blair, product manager for UAP Canada, Rancona Apex has become a popular option away from Vitaflo, both for its control of loose smut and cochiobolus sativus, the fungal pathogen that causes some fusarium-like seedling blight.

“Rancona is really good on a lot of these diseases,” says Blair, who is based in Winnipeg. “It does have systemic and contact activity, so it will provide good control of soil-borne seedling disease as well as disease that’s inside the seed, like true loose smut or loose smut.”

Another property that makes Rancona a popular choice, says Blair, is its flowability. It behaves like a true liquid, making it easy to apply for growers who do the job themselves. Its formulation also allows for treating seed at temperatures as low as -20 C without having to worry about lines freezing. That means seed companies and growers can get a jump-start on the season, even in the middle of winter.

Seeing and believing

For Quentin Martin, finding the best solution to loose smut in barley is particularly important. As principle of Cribit Seeds and Wintermar Farms, northeast of Waterloo, Ont., Martin is a seed grower and processor of various cereals, so his customers’ livelihoods — and his own — all depend on effective disease control.

In 2011, Martin participated in a seed and foliar treatment trial at three sites (Winterbourne, near his home farm, Conn and Newcastle). He cautions that although this was an extensive replicated trial with 360 total plots, it was the first of two years for this study, which was funded in part through the Growing Forward initiative, with the help of the Agricultural Adaptation Council and several private- and public-sector partners. The results for loose smut in barley were encouraging, but data were gathered from the Winterbourne and Conn sites only.

“The main focus was looking at DON (deoxynivalenol) levels in oats and barley, and looking at the new seed treatments and the new registrations for foliar fungicides for oats and barley,” says Martin. “And the tests afforded us the opportunity to do some smut counts as well.”

In fact, Martin notes the most conspicuous results from 2011 did not come from responses to foliar fungicides or seed treatments, it was from their tests for loose smut. In the introduction on the test’s report, Martin pointed out that 2011 “was a very challenging year for oats and barley production, because of the late, wet spring conditions followed by a hot, dry summer.” That actually affected the results at Newcastle but provided some solid evidence that the issue with loose smut is related to weather and environment, with disease conditions at Conn worse than those at Winterbourne.

“We worked with Dignity barley,” says Martin, noting that the variety out of Duane Falk’s program at the University of Guelph is one of the higher-yielding, six-row barleys available to growers in Ontario. “It’s a good variety for tracking smut, and we were looking for disease control in oats and barley. Ironically, the disease that produced the clearest results in the test was loose smut.”

Dignity is a relatively new variety and Martin concedes that loose smut flourished under suitable conditions.

“We’d used Vitaflo for 25 years in spring cereals, but in 2011, we switched to Rancona and did see improved performance with it,” Martin says. “In this research work, we were able to look at things much more closely and going to Rancona was the right choice for smut.” CG

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