If it’s wheat, spray for fusarium

This disease has become a perennial issue — and it will be for years to come

With today’s tight margins, there are times when it can make sense to play the odds in order to cut spray costs, at least until there’s visible damage to the crop. But with fusarium head blight in wheat, it’s just not advisable.

Peter Johnson believes it’s time to adopt the same caution with fusarium as with soybean cyst nematodes in much of Ontario, or with white mould on beans in the east. You just can’t plan on winning that bet.

This coming season will mark 20 years since the 1996 disaster that decimated fields across Ontario, with 90 per cent of the province’s winter wheat downgraded due to fusarium.

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It could happen again. In 2016, fusarium remains a risk. The days when farmers could say “not-this-year” are all but gone. So if you’ve got wheat, Johnson says, spray it and be done with it.

In the past five years, there has been a significant shift in disease thinking, particularly in wheat. Low commodity prices convinced more growers to take a chance on fusarium, a move which Johnson, an independent agronomist, believes to be unwise, pointing to 2015 as an example.

“It was a poor wheat crop, a tough winter, with late-planted wheat and 12 to 13 per cent taken out and replanted because it just wasn’t good enough to keep,” Johnson says. “And then with a really dry May, I had producers calling me up, saying, ‘Why would I waste money on a fusarium fungicide? My yield potential is low and my disease risk has to be low because we’ve had no rainfall.’”

Johnson could see their logic, yet he still advocated spraying for fusarium. He estimates as many as 80 per cent of growers in Essex County and a little less than half of producers in Kent opted to roll the dice and skip spraying for the year.

Then it started to rain.

Johnson recalls one grower who delivered his wheat, took a tremendous grade discount, paid for the crop to be dried, and was left with a net 80 cents per bushel on yields of 80 bu./ac. — just $64 per acre.

“We simply cannot predict the conditions,” Johnson says, adding that the same scenario played out in 2014, with a poor wheat crop and dry conditions in May (although not as dry as May 2015). “I wasn’t getting as many calls, but still had some, and the exact same thing happened.”

The difference in that 2014 crop was the large-scale planting of Pioneer 25R40 the previous fall. Unfortunately, there wasn’t a lot of fusarium data available for that variety, and a lot of producers liked what they saw of it, and accepted the risk. Then the right weather conditions developed, particularly in a region bounded by Grand Bend, Exeter and London — a swath that became known as “The Black Triangle.”

Indeed, Johnson says, the last two years have really driven home the damage that fusarium can do.

This head is gone too far for spraying for fusarium. Instead, spraying needs to be part of the annual management plan.

This head is gone too far for spraying for fusarium. Instead, spraying needs to be part of the annual management plan.
photo: Supplied

“We’ve seen how the use of fungicides changes the nitrogen response curve,” he says, pointing to work he has done with Shane McClure. “It’s very clear that in order to make wheat profitable, you need to use higher rates of nitrogen, and if you don’t spray the fungicide, you don’t get a response to the added nitrogen.”

Besides, even with DONcast, no technology can predict the weather perfectly. That’s why Johnson says it makes sense to remove the uncertainty, by spraying your wheat every year.

“If every farmer in Ontario quit growing corn for five years, maybe — and it’s a big maybe — we would reduce the inoculum loads,” Johnson says.

“But we’re not going to stop growing corn, nor should we… so we are going to have enough inoculum potential regardless of what we do.”

In other words, if the weather conditions are right for the disease to develop, then everyone is going to get hit.

Aren’t things challenging enough?

Full-maturity soybean varieties are also affecting fusarium rates. In the past five years, farmers have been told to extend the maturities on their soybean crops, even if it means delaying planting winter wheat.

Johnson doesn’t favour this at all.

“We grow close to three million acres of soybeans in this province, and we struggle on a perfect fall like last year, where I was sure we’d break a million acres of wheat,” he says.

“I can grow long-season soybeans on two-thirds of my soybean acres and max-out on yield. Yet how is it that I can’t spread out my soybean harvest well enough that on the third of the acres that are going to wheat, I plant them earlier and I go with a little shorter-season variety of soybeans so that I get my wheat in in decent time?”

Besides, long-term research shows a good wheat crop in the rotation leads to a proven five bushels more in rotational soybean yield. The boost in corn isn’t as quantifiable, but the field studies conducted at University of Guelph’s Elora Research Station and at the university’s Ridgetown Campus are undeniable: wheat in the rotation means more bushels of soybeans.

Asked if the genetics used in wheat are contributing to higher fusarium rates or if the disease is becoming more resistant to fungicides, Johnson points to two factors affecting the genetics: no GMO wheat technologies are available to growers, and there is a big disparity between the level of investment in cereal breeding compared to corn and soybeans. And that’s not just in Ontario, but globally as well.

“There’s about one-tenth the amount of dollars invested in wheat breeding,” says Johnson.

Toxins that can be produced by fusarium remain a marketing challenge.

Toxins that can be produced by fusarium remain a marketing challenge.
photo: File

The role of genetics

“As an agronomist, all I can do is support the increased yield potential that the breeder is giving me in a new variety, so they’re doing a tremendous job, but if we multiplied that effort times 10 would we make much faster progress? Would we have higher levels of success? I have to believe the answer is yes.”

Still, there has been some genetic progress in winter wheat, particularly in Ontario. The varieties are all rated on gocereals.ca, and as of the latest ratings, none was listed as “highly susceptible” to fusarium. That’s a first in the province’s history. There were highly susceptible varieties in the test, but sponsors know those are almost unmarketable, so they weren’t made available.

“We have had significant improvement over time on average in our wheat varieties’ resistance,” agrees Johnson.

“But even with that, the pressure is such that genetics alone can’t do the job — they just aren’t good enough. So even though we’ve done amazingly in terms of moving the bar forward, it’s not enough.”

It’s one thing to make the application of a fusarium fungicide an annual management practice, but it’s also important to rotate chemistries, something that agronomists, chemical company representatives, weed scientists and extension personnel have been advocating for years.

Yet Johnson finds farmers tend to be creatures of habit. If they used Carumba (metconazole) three years ago on their last winter wheat crop, they’re likely to stay the course with Carumba in 2016.

The problem with that approach is that New York had its first case of a strain of fusarium that is resistant to Folicur (tebuconazole), one of the actives (with Proline or prothioconazole) in Prosaro.

Thus far, there is no resistance to prothioconazole or metconazole.

“From a resistance management strategy, farmers should go back to their records and say, ‘If that field was in wheat three years ago, and it got Prosaro, this year I’m going to use Carumba’,” says Johnson. “Most growers aren’t doing that, and from a resistance management perspective, that’s a mistake.”

About the author

CG Production Editor

Ralph Pearce

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