Sclerotinia, that nasty fungus that can cause as much as 50 per cent yield loss in a tough year, poses a particular problem for many farmers. Not only is it found across the Prairies, several common crops are susceptible making crop rotations nearly useless for control. Capable of knocking back canola, dry bean, lentil, soybean, sunflower and alfalfa, sclerotinia levels in some fields have drastically reduced cropping options.
That is, until now. Last year a novel disease control product was rolled out for Western Canada. Contans is a pre-emergent biofungicide — a parasitic fungus — that actually feeds on and destroys sclerotia. Sclerotia are dark, hard, resting bodies of the fungi that overwinter in the crop residue and the soil. Each sclerotia body can release millions of spores in the growing season.
United Agri-Products (UAP) introduced Contans in 2010. The active ingredient in Contans, Coniothyrium minitans,is a natural predator of sclerotia bodies, says Ken Coles, general manager at the Southern Applied Research Association (SARA) at Lethbridge, Alberta, who has headed up research on the product.
Because of its novel nature — Contans is applied prior to the susceptible crop being grown and needs up to 90 days to clean up a field — Coles and his colleagues have been working identify best management practices to prevent sclerotinia on canola and white mould on dry beans. So far, he says, the research has hinted at positive results in some fields — particularly in dry beans.
Work at SARA seeks to pin down when and how Contans is best applied to the soil for best control. Incorporation methods are important, as Contans must come into contact with the sclerotia in the soil in order to be effective. It’s also a living organism so it must be incorporated quickly, or the fungus can die from sunlight exposure or by drying out.
“Under zero-tillage systems, farmers can use moisture as an incorporation method,” Coles says, “either by spraying on Contans or by timing its application with rainfall.” Contans is available as a water-dispersible granular formulation that can be tank-mixed with several different herbicides. Contans is active between 5 C and 30 C. Outside of this range, the fungus goes dormant.
Coles says farmers using minimum or conventional tillage must pay close attention to moisture levels. “If a tilled field is dry and lumpy, Contans won’t come into contact with the sclerotia nor will it survive,” he says. “Contans is little more management intensive than your typical silver-bullet chemical fungicide.”
Brodie Blair, western product manager for UAP, says that handling Contans is going to take a bit of getting used to for farmers. Because it’s live, Contans is kept frozen in order to keep it dormant until it’s in the field. As a result, it has to be applied quickly.
Nor does Contans work instantly. Temperature-dependent, Contans requires time to to render sclerotial bodies unviable. Depending on the weather, cleaning up a field could take up to 90 days.
Blair says that, depending on infection levels and planned crop rotation, a fall application may be best to “allow it a little more time to start working.” Blair says spring applications are more expensive, requiring the higher rate of product (0.8 kg/acre and $26 per acre) to ensure enough parasitism to make a difference. A fall application requires only 0.6 kg/acre ($18 per acre), because of the longer timeframe for the fungus to work at eating up sclerotia.
In trials at SARA so far, the fall weather has made it difficult to get the product on and as a result, the fall application results haven’t impressed Coles. He thinks fall conditions on the Prairies might be “too tight and too tough” to apply Contans properly. He says that a spring application following a susceptible crop might work best.
Contans reduces the sclerotia loads over the long term so farmers may not see benefits for a couple of years. Because Contans is applied to the residue of an infected crop, the grower sprays it on a field that is going into a non-susceptible crop, such as wheat. Essentially the grower is investing in the next susceptible crop that’ll be grown in that field a year or two down the road. Coles admits this approach can be a tough sell to farmers.
But Blair says that because Contans continues to work in the fall, spring and through the growing season, “an application of Contans is never wasted.” Even if a farmer doesn’t see immediate results, it will help decrease sclerotia levels over time. Blair recommends that growers build a base of Contans in their fields. Once it has been established, they can move into maintenance mode, applying about .2 kg per acre each year, which would cost less then $10 per acre.
FIELD-SCALE EXPER IENCE
Contans was applied to about 15,000 acres across the Prairies in 2010. Blair says the reaction has been positive from farmers who tried it. He also says field-scale results at a trial at Hudye Farms in Norquay, Sask., were positive. Soybean trials by Vikram Bisht with Manitoba Agriculture Food and Rural Intiatives also yielded positive results.
Both Blair and Coles are fairly optimistic about the continued trials for Contans for the 2011 season. Coles hopes that another year of trial results will point towards clearer best management practices. He does feel, however, that the product will have a tough road ahead because researchers have to not only demonstrate that Contans works, but that it “makes sense economically.”
Bean growers may be keen to try Contans, since white mould is their primary limiting factor, but canola growers might be more hesitant. According to Coles, using a biofungicide like Contans requires a shift in mentality; farmers have to get used to the idea of investing in a crop that’s two years down the road instead of expecting immediate results. Though he thinks it’ll be a few years before we figure out the full benefits of Contans. “If we want to make progress in the industry, producers will have to take the time,” Coles says.