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Attack fusarium head blight head on

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

A new fungicide may reduce the damage caused by fusarium head blight.

Like a seasonal illness, wheat growers have come to accept fusarium head blight as an unfortunate and risky fact of life. Unlike head colds, though, 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 in Ridgetown, Ontario. “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 cascade 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 mycelium or spores in crop debris. It can also affect seedlings upon emergence through the debris. Wind and rain-splash can further spread the spores to the above ground 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.
 

While there is no magic bullet, management can help with FHB control. (Photo courtesy of Department of Plant Science, University of Manitoba)

Advances in FHB 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 in the winter wheats adapted to Eastern Canada,” says Hooker. “In those Eastern wheats, 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. Unfortunately, the vast majority of spring wheat varieties produced in Western Canada are still susceptible to the disease. However even for varieties with resistance, fungicide options and other agronomic tools are still recommended to minimize risk.”

Good production practices are also key to stemming the spread of disease. According to Manitoba Agriculture, Food and Rural Initiatives (MAFRI), there is little that can be done to manage the spore load in field trash. Burning and tillage have little effect, particularly given the mobility of the spores. But a well-managed rotation, with a break of at least one or preferably two years, between cereal, grass and corn production is advised.

MAFRI also recommends that growers select less susceptible cereal varieties for their rotation. It is important to remember that not all cereals are equally resistant. Durum is the most susceptible cereal, followed by Canadian Prairie spring, hard red spring, barley and oats, in improving order.

Another area of progress is fungicides. Caramba, a new systemic triazole innovation from BASF, has performed very well in his replicated field trials, says Hooker. “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 total control, but Caramba consistently achieved between 50 percent to 70 percent control” when applied properly.

Caramba also delivered some of the strongest control of leaf rust and stagonospora glume blotch. 

Ray Mazinke of Morris, Manitoba, was part of a grower-applied research trial in 2008. He compared wheat treated with Caramba with wheat left untreated. His results were enough to pique his interest and make him consider wider-scale use of the fungicide on his operation, pending product registration.

“You wouldn’t even have to be in the business of farming to look at those two samples and notice that there was a difference,” Mazinke says. What is more, he adds, the wheat treated with Caramba yielded roughly 10 percent better than the untreated wheat.

Application timing and application technology are two additional factors that are critical to maximizing the benefits of more of the most effective fungicides.

With respect to application methods, BASF field-scale trials with Caramba demonstrate excellent results with both aerial and ground application equipment. When applying by ground, the best results have been achieved using spray nozzle configurations such as TwinJet and Flood Jet nozzles that target the wheat head. Due to the relatively narrow application window (at flowering) some growers appreciate the flexibility aerial application provides, and BASF trials using Caramba have shown this spray method also to be very effective in reducing disease levels and improving yield.

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 properly treated with an effective fungicide if conditions warrant its application, is the best way for growers to protect their wheat production.