By Andrea Hilderman
Managing fusarium head blight (FHB) incorporates overarching considerations around crop planning, variety selection, utilizing decision support tools as well as spraying fungicides in-season to suppress the organism actively growing on the crop. By looking at it in this more global way, many growers have been able to harvest clean, high-yielding crops despite the disease being present.
In Manitoba, growers have been dealing with FHB for longer than those growers in Saskatchewan and Alberta. Rather than reinventing the wheel and learning from scratch, those growers have the benefit of learning from Manitoba growers and advisors who have adopted a range of FHB fighting tools that are successful in keeping yields up and quality as high as possible.
“Managing FHB on our farm starts with crop planning,” explains Randy Court of Court Seeds & Greenhouses based out of Plumas, Man. “That means considering field rotations, variety selections and tillage methods.”
One aspect of Court’s approach is looking at ways of reducing inoculum levels. “FHB is basically a mould,” he says. “The more trash there is with the right conditions and FHB will grow and reproduce, and be a source of disease in future years.”
Holly Derksen is the field crop pathologist with Manitoba Agriculture, Food and Rural Development (MAFRI). Her advice follows the same theme as Court. “FHB is best managed by multiple strategies,” says Derksen. “Crop rotation, tillage, planting dates, days to maturity, genetic resistance, seed treatments and fungicides should all be considered as a package to manage FHB in the field. No one strategy alone will be successful, but all together will yield results.”
Both Court and Derksen think most everyone understands the rotation message. “This is as simple as avoiding back-to-back cereals in the rotation and especially avoiding putting spring wheat on corn stubble,” explains Derksen. “Corn stubble takes a long time to decompose, more so than cereal stubble, so it acts as a source of infection for a much longer time.”
That said, it is not necessary to completely eliminate all stubble, as infection can occur under ideal conditions from headlands or spores carried on the wind. Derksen notes that central and eastern Manitoba in particular have had lower levels of FHB over the last two years due to environmental conditions not favouring disease development. However, the fusarium organism can cause other diseases such as root rots on a broader host range and that will replenish inoculum.
“There is more than sufficient fusarium present to cause FHB if conditions present as favourable,” warns Derksen.
Preventing infection by using genetic resistance is an important tool in the FHB management toolbox. There has been considerable emphasis in breeding programs to developing and commercializing genetic resistance to FHB. “Spring wheat varieties exhibit a range of resistance to FHB, all the way from susceptible to MR, or moderately resistant,” says Derksen.
The 2013 Manitoba Seed Guide data for spring wheat indicates that the highest rating so far for varieties is MR. There are no resistant or R rated varieties available. There are eight Canada Western Red Spring wheat varieties with MR ratings.
“But it’s important to realize that MR rated varieties, or even one that might be rated R, can be infected and will sustain disease damage under high levels of disease pressure combined with ideal conditions,” notes Derksen. The other aspect of variety selection is looking at staggering days to maturity and planting dates to ensure not all the crop is flowering at the same time.
“Seed treatments are a very important part of my management strategy for a host of reasons, but when it comes to in-crop control of FHB, I don’t rely on seed treatment alone,” says Court, who adds that while seed treatment is critical to establish a healthy, uniform plant stand and prevent soil-borne fusarium seedling infections, which result in damping off, seed treatments won’t prevent FHB infection at flowering.
“A healthy, uniform stand will give you a yield advantage but also it’s important at the time I spray for FHB in-crop,” he notes. “It increases the effectiveness of the fungicide because more of the crop is at the right stage when I am spraying.”
In his experience, Court feels some growers are looking to seed treatments to control FHB in-crop, and that is not what seed treatments are designed to do.
This takes us to the next tool – spraying in-crop for FHB disease control. “Assess the risk,” advises Court, who determines whether he is going to spray long before he seeds. “The decision to spray can’t be made in-crop because you can’t actually see FHB until it’s too late.”
Court’s own philosophy is born out of his business, growing seed. “Yield is only a small part of what Court Seeds is all about,” he says. “My family business is all about quality targets. Everyone knows seed has high quality standards to meet; however, I believe all growers should be looking at it the way we do.”
Court estimates it might cost $15/acre to have fungicide custom applied. “At today’s commercial prices, a guy only needs to get two more bushels to cover that cost,” he explains. “And that is not even taking into account quality.”
Court’s view on farming generally is to maximize returns, not minimize costs. “I know what my fields are capable of and I will throw the inputs at the crop to maximize returns,” he says. “Bankers and accountants are pressuring guys to reduce costs, but that is very short-sighted in my opinion.”
Court also operates a seed-cleaning plant and does custom seed cleaning for local farmers. “I see quality that is unbelievable compared to what we took off,” he says. “This is why I think everyone should spray for FHB whether or not the conditions and the decision support tools says risk is low. I see it in improved quality year-in and year-out.”
Derksen agrees, adding that timing is critical when spraying for FHB. “There are a number of decision support tools, including MAFRI’s FHB Forecasting System,” she notes. “Weatherfarm is another and North Dakota has one too. Check all these tools, not just one, to assess risk. Flowering occurs very quickly so you have to be out in the fields scouting.”
Court concurs. “What I do is check those areas of my fields I know flower first,” he explains. “I know this from experience, but it’s usually the headlands. Every farmer knows this. This helps me gauge when the rest of the field will flower.”
He then keeps going back to those same spots to check progress until such time as flowering is occurring on the main stems. “At that point, I start estimating flowering in the main part of the field, twice a day,” he says. “I look only at the main stems, and once I determine 20 percent emergence, we start spraying. From seeing the first flowers in the main areas of the field to 20 percent flower could be less than a day, so you have to be on the ball with scouting and having your custom sprayer or your own sprayer ready to go.”
Court and Derksen agree that without this level of precision when it comes to spraying for FHB, a grower is wasting money. They also agree that this is where the staggered days to maturity and seeding dates can give the farmer the time required to get the entire crop sprayed at the right time.
To summarize, Derksen has another warning for growers. “Fusarium is not a static disease in the sense that it is capable of, and does, change,” she explains. “We know there are a number of species of fusarium, the most prevalent of which is Fusarium graminearum. What we’ve seen is the more aggressive chemotypes of Fusarium graminearum becoming even more prevalent.” What this shows is that growers can never let their guard down with this organism, and constant vigilance and management is always necessary.