1. Get smarter about sclerotinia
Luis del Rio, canola pathologist and associate professor at North Dakota State University, has worked with other researchers on sclerotinia in canola and other crops. The same sclerotinia species can infect many dicot crops, including canola, sunflowers and soybeans. A tight rotation that includes two or more of canola, sunflowers and soybeans is like “playing with fire,” del Rio says.
Sunflowers are particularly noteworthy for the potency of their sclerotia, the hard black resting bodies produced when sclerotinia infects plants. Not only are sunflower sclerotia much larger than canola sclerotia, but the apothecia that emerge from these sclerotinia also produce more potent spores, del Rio says. “It could be that sunflowers provide a better source of nutrient for sclerotia,” he says.
In his Canola Discovery Forum presentation, del Rio also talked about “effective transport” of spores and the lifespan of sclerotia in North Dakota and Western Canada soil conditions. While a small percentage of sclerotia spores can travel up to a kilometre or more with the right wind conditions, the amount needed to cause disease will travel only about 40 metres from the source apothecia, del Rio says. This is what he calls “effective transport”. Therefore, most sclerotinia infection will come from apothecia emerging within the field or immediately adjoining fields.
He also says sclerotia can last for two or three years in soils with high
microbial activity (rich moist soil) and longer in soils that have less microbial activity. He adds that sclerotia from last year will have the highest potency, with potency dropping over time — similar to seed germination. While sclerotia three years old could still produce apothecia, these are not likely to produce many spores. “With rotation away from host crops, growers are buying time for enemies of sclerotia to attack, weaken and kill them,” he says.
What does this mean for management? One idea is that Contans, a soil-applied biological that can kill sclerotia, might prove effective after sunflowers. Current thinking is that Contans would have to be used over a wide geographic area to provide any meaningful reduction in sclerotinia risk, given the number of host crops grown each year, but localized measures (even field by field) to reduce the potency of sunflower sclerotia might be worthwhile.
Discovery Forum also had a presentation from Lone Buchwaldt, research scientist with Agriculture and Agri-Food Canada in Saskatoon, who provided an update on genes identified in v that contribute to sclerotinia resistance. Nine of these genes have been cloned and transformed into a susceptible canola line to measure the contribution of each gene by itself. One gene, found in a Pakistani line, is particularly interesting as it could reduce the penetration of the pathogen into the plant cell.
2. Map acres that never make money
Many farms have the data needed to produce profitability maps for their fields. Add grain prices to yield maps to provide a revenue map, then subtract inputs to produce a profitability map. Mapping software and consultants can help with this.
Brian Arnall, precision farming extension specialist with Oklahoma State University, says three to 10 per cent of each field loses money every single year. Growers could turn off nutrients and fungicides in these areas, providing a relatively simple way to improve return on investment for inputs and overall field profitability.
“It blows my mind that this is not commonplace,” Arnall says. “This will be my major extension program for the 2017 calendar year.”
This tied in well with an unrelated presentation later in the program from Lora Morandin, Western Canada program manager for Pollinator Partnership Canada. She spoke about the benefits of maintaining habitat around the farm for pollinators and other beneficial insects. Perhaps unprofitable areas could be seeded to flowering plants and shrubs, creating the habitat necessary for beneficial insects that can improve yields and reduce insect management costs. Find out more at pollinator.org.
3. Select the right root for the job
Like the human gut, which is full of microbes that help us digest food, expel bad germs and influence our overall health, the plant root area – the root “microbiome” – is a similarly diverse ecosystem. A gram of soil can have as many microbes as all the humans on Earth, and we’re just starting to understand how these root-zone organisms work with or against plants.
Bobbi Helgason, soil microbiologist with Agriculture and Agri-Food Canada (AAFC) in Saskatoon, spoke about new tech-driven opportunities to use DNA sequencing to discover the diversity of this ecosystem and identify organisms beneficial to canola. “We want to first understand the signals plants use to recruit and interact with beneficial organisms, and then to figure out how this beneficial niche is linked to plant genomics,” Helgason says.
While Helgason works on the soil microbe side, Sally Vail, canola breeder and genetics researcher at AAFC Saskatoon, explores the plant’s perspective. “We know environmental differences exist that influence the root microbiome,” Vail says. “We want to test the hypothesis that plant genetic differences are microbiome controllers as well.” The microorganism community can vary by environment and location, but AAFC researchers may discover that within genetically diverse canola lines, some root traits are better suited to certain microbiome conditions or work better with specific organisms.
“It could be years down the road, but if farmers knew the soil microbial community in their fields, they could choose canola varieties with genes equipped to most beneficially take advantage of that microbial mix,” Vail says.
This will also improve our understanding of “soil health”. While answers may take time, Helgason recommends that farmers continue to take steps to preserve the healthy and diverse soil ecosystem currently present in their fields. Reduced tillage and crop rotation practices that promote healthy crops are two such steps.
4. GRADE the validity of evidence
Dr. Roger Suss provided a doctor’s perspective on weighing evidence when advising patients. He gave a brief introduction to the Grading of Recommendations Assessment, Development and Evaluation (GRADE), an outline the GRADE working group developed to standardize what was meant by an “A” level of evidence, for example.
With any evidence, whether for medical health or agriculture, users need to know its validity. Internal validity of a study refers to the integrity of the experimental design. External validity of a study refers to the appropriateness by which its results can be applied to non-study patients or populations.
“Science is based on the assumption that if you repeat a process precisely, the same thing will happen each time,” Suss says. “This works well when you can control all of the variables, but in medicine we never control all of the variables. We try to control as many as we can.”
Agriculture would be the same, with many variables that can test the external validity of research.
“External validity is about whether extrapolation is reasonable or not, and is a judgement call based on “experience” and other vague criteria,” Suss says. “If a treatment worked in Philadelphia will it work in Winnipeg? How about in Darfur? Disease is pretty similar in all developed countries and different in poor countries. But humans are pretty similar everywhere. I am comfortable assuming that most treatments that worked in Philadelphia will work in Winnipeg. The extrapolation seems small.”
Suss provides the following advice for doctors weighing harms and benefits. “If someone has done a study that weighed harms and benefits in a way that you feel has external validity to your situation, then the question is answered. But frequently evidence of harms and benefits may come from separate studies. Then, my advice is mostly to think about both sides of the balance and attempt to “weigh” each. We often fail to do that. We just look at one or the other. Or we change the question (often with the encouragement of industry) to say ‘is there any benefit’ rather than actually measuring the magnitude of the benefit,” he says. “I imagine much of that applies to farmers, too.”