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Attack fusarium head blight head on

Finding a way to better manage fusarium head blight would be like finding a cure for the common cold, except it would do more than prevent nuisance aches and sneezes. It would save millions of dollars in lost yield and quality annually.

By reducing the incidence of fusarium head blight in wheat, growers will benefit from increased yields, better quality seed and peace of mind. Photo courtesy of BASF.

Like a seasonal illness, wheat growers have come to accept fusarium head blight as an unfortunate and risky fact of life. Unlike head colds, however, there has been recent progress in stemming the spread of the disease. Since the cereal disease first made its appearance more than two decades ago, new practices and new wheat varieties have helped curb the spread of fusarium head blight. And, a new fungicide in the fight against fusarium is now on the radar. “Today we have more options and more tools to manage the disease, although we still cannot achieve 100 percent control when conditions are favourable for infection and disease development,” says Dr. Dave Hooker, field crop agronomist at the University of Guelph’s Ridgetown Campus. “Every year, there are at least some growers, somewhere who suffer tremendous losses due to fusarium head blight.”

Those losses start with yield: a 20 percent infection rate can reduce yield by up to 20 percent, says Hooker.  And other problems follow from there. Infected seed commands lower prices, has lower feed and processing value, and if reseeded, typically results in a thinner, less vigorous crop.

Weathering the weather
The real challenge of managing fusarium head blight is that so much of its spread is dependent on the weather.

Head blight in wheat, which is caused by the fungus Fusarium graminearum, overwinters as mycelia or spores in crop residue. It can also affect seedlings upon emergence through the residue. Wind and rain-splash can further spread the spores to aboveground portions of the plant and across fields.

Humid, warm conditions, between 10 and 30 degrees C, five to 10 days before wheat head emergence favour the development of the spores, which can infect the heads at flowering if warm and moist conditions persist.

Advances in fusarium head blight management
But if there is no cure, there is still room for optimism. “Wheat breeders have made tremendous progress in developing some resistance or tolerance to the disease,” says Hooker. “In winter wheat today, we have a handful of varieties that are moderately resistant to the disease. A decade ago, nearly all varieties ranged from susceptible to highly susceptible. However, even for varieties with resistance, fungicide options and other agronomic tools are still recommended to minimize risk.”

Good production practices are also fundamental to stemming the spread of disease. According to the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), the best way to manage all diseases, including fusarium head blight, is a sensible rotation.

Outbreaks occur because three things are present in a field: the pest (in this case, fungal spores), the host crop and the right environmental conditions. The grower cannot control the weather, so the two top management practices for reducing the risk of infection are to choose a wheat variety with some resistance to the disease, and to avoid planting wheat after corn.

OMAFRA recommends growers consider planting more-tolerant varieties of wheat. Clean plowing of infected trash has very little effect, say the Ministry guidelines, but the risk of infection from nearby fields remains high if weather conditions are favourable.

Another area of progress is fungicides. Caramba, a new systemic triazole from BASF, has performed well in Hooker’s replicated field trials. “In our trials, Caramba was one of the top fungicides for reducing the visual symptoms of fusarium head blight and for reducing deoxynivalenol (DON) mycotoxin concentrations in winter wheat,” Hooker says. “No fungicide achieves 100 percent control, but Caramba consistently achieved between 50 and 70 percent control” when applied properly. Caramba also delivered some of the strongest control of leaf rust and stagonospora glume blotch.

Dave Eadie, who farms near Lucknow, Ontario, was part of a grower-applied research trial in 2008. He compared Caramba with Proline on side-by-side, 20-acre plots. For his farm, he wanted to see which product delivered the best fusarium control and which improved yield. With Caramba, he says, “We got both.”

Both stands looked similar, Eadie says, but the real difference came at harvest. “The yield on the Caramba test strip was 124 bushels, and on the Proline, it was 119 bushels. Yield wise, it was exceptional; that’s the best yield I have ever seen out of my winter wheat.”

Application timing and techniques are also as important as the fungicide itself. If not applied properly, results may not be satisfactory if weather conditions are favourable for the disease. Pioneering work from Hooker and OMAFRA suggests that the best approach is to use nozzles that spray the wheat heads nearly horizontally, from the front and from the back, using a high water volume. This ensures the most uniform coverage of the wheat head. Conversely, application trials show that the effectiveness of the fungicide can be reduced with the use of conventional nozzles that spray downward.

Clearly there is no magic bullet for the control of fusarium head blight, but the various tools available to manage the disease have improved significantly. A sound rotation that includes the use of the right wheat varieties, and proper treatment with an effective fungicide if conditions warrant its application, is the best way for growers to protect their wheat production.