Soybean and corn disease threats in Eastern Canada

Growers will need to use all their experience, best management practices and new tools to successfully combat disease in 2020

Sudden death syndrome is expected to worsen in southwestern Ontario soybeans and root rot could also be a serious concern this year if the conditions at planting time are wet.

Another crop season is upon us and certain disease threats stand out in soybeans and corn in Eastern Canada.

“SDS (sudden death syndrome) is expected to worsen in southwestern Ontario soybeans and root rot could be a serious concern this year if the conditions at planting time are wet,” notes Dr. Owen Wally, research scientist in field crop pathology at Agriculture and Agri-Food Canada in Harrow, Ontario. “White mould may be a threat later in the growing season if the weather is cooler and wet later on, but current fungicides are effective with this disease.”

Bayer’s eastern market development representative Bryan Bryson agrees that SDS and white mould are the main soybean diseases of concern this year in Ontario and Quebec, and adds that there may also be some SCN (soybean cyst nematode) issues. “Bayer does genetic screening for SDS and white mould in Eastern Canada to understand our soybean varieties’ response to these diseases,” he explains. “Starting with genetics that are adapted to the disease challenges facing a grower is the base of an effective disease-management strategy. Growers should be careful to pick the correct genetics and use multiple varieties.”

Bryson adds that in the case of SDS, seed treatments offer complementary protection to the “base” genetic resistance of the best-chosen varieties.

White mould management

For white mould management, proper genetics are also the first step, but obviously growers need to use appropriate planting density, row spacing and fungicide applications. Using previous years’ experience along with scouting notes is also a must in identifying fields where disease pathogens are present and to what extent. Overall, Bryson advises growers that “working with local seed dealers, government extension workers and Bayer staff will help growers to select the right genetics, seed treatments, planting agronomics as well as manage fungicide application decisions to create tailored solutions.”

DON pressure on corn is a function of the “disease triangle” of environment, host and pathogen. photo: John Greig

In terms of DON presence in Ontario and Quebec this year, you can consult the Ontario Provincial corn ear mould and mycotoxin survey, completed by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) in collaboration with Grain Farmers of Ontario and members of the Ontario Agri-Business Association. In October 2019, Ben Rosser and Albert Tenuta, OMAFRA corn specialist and field crop pathologist, respectively, reported that 96 per cent of samples in the survey tested “low” (under 2.00 parts per million) for DON, considerably lower than the results of 2018. However, the surveys each year do not include every field in the province, and Rosser and Tenuta also note that timely harvest is important. Leaving diseased grain in the field allows the ear rot fungi to keep growing, which will increase the risk of mouldy grain and mycotoxin contamination since most ear rot fungi continue to grow (and potentially produce mycotoxins) until the grain has less than 15 per cent moisture.” In Quebec, some of the 2019 corn harvest was completed in January 2020.

The “disease triangle”

While every farm’s situation will be different every year for DON, Bryson reminds that pressure for it or indeed any disease is a function of the “disease triangle” of environment, host and pathogen.

“If growers have had a history of DON pressure in past years, they should be on the lookout for it in 2020. The reality of this triangle is that we can’t control two of three of these elements (environment and pathogen presence), but the ‘host’ is under our control. That is, the best germplasm is the starting point.” In 2019, Bayer started screening its corn genetics in Eastern Canada to understand differences in disease response.

Bayer’s row crop agronomic systems manager Adam Pfeffer adds that “In addition to choosing the best hybrids, using multiple hybrids to spread out the risk on your farm is also a good strategy from a genetic diversity and flowering date standpoint.” And as with soybeans, he says that depending on weather this spring, tailored DON control in corn includes scouting for disease development and having an effective fungicide strategy at the ready.

Fungicide timing

Pfeffer reminds growers that if they need to control white mould in soybeans, R1 would be the target for the first fungicide application. “For DON control in corn, silking is the key timing and in cereals, anthers present in the middle of the head is the staging to look for,” he explains. “As with any application, scouting for crop stage and disease presence as well as paying close attention to rainfall and forecasts are key elements to consider.”

Determining the level of disease pressure can be aided by the use of the latest technology. The FieldView platform, for example, allows growers to use satellite imagery to identify problem areas in their fields (spots with less biomass) that may otherwise go unnoticed. The FieldView app also shows growers where they are located in the field in real time, enabling growers to quickly move to problem areas and therefore making scouting as fast and efficient as possible. Any problem areas are effectively monitored over the season and also can be compared to what was present in past years.

“The Climate ‘Field Health Imagery’ in FieldView could definitely be used to help identify thick parts of the canopy in time enough to scout the field before growers run out of management options,” Pfeffer says. “Field-specific rainfall and temperature conditions for each field are recorded as well, and this is a big help to growers in determining what the level of disease pressure may be, and where, on their farms.”

This article was originally published in the 2020 Disease & Yield Management Guide, a Country Guide Special supplement sponsored by Bayer Crop Science.

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