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Soybean cyst nematode survey a valued benchmark opportunity

The word nematode is often linked to soybean cyst nematode (SCN), and with good reason. In North America, SCN accounts for annual losses of more than $1 billion and up to $50 million in Ontario.

A survey of field and horticultural crops across the province seeks to update provincial nematode distribution maps and establish baseline data for six different nematode species including SCN.

Why it matters: There are gaps in nematode awareness and management options so survey data can be used to help farmers better manage problems.

Albert Tenuta, field crops pathologist, and Katie Goldenhar, horticulture crops pathologist with the Ontario Ministry of Agriculture, Food and Rural Affairs, are working on the survey. Target species include SCN, root lesion and other nematodes, and the project doesn’t place any higher importance on one versus another.

“The results will support the enhancement of current nematode best management practices for field and horticultural crop farmers,” says Tenuta. “Participating in the nematode survey is free, easy, and soil samples can be collected specifically for nematode testing or alternatively, soil samples collected for soil fertility can be split.”

“The yield impact of many nematodes, such as cyst, needle, stunt, root lesion, lance, stubby and pin, on Ontario’s horticultural and field crops has been ignored, misdiagnosed or not well understood” says Tenuta.

“Compounding these issues is nematodes are difficult to identify in the field since many of the typical symptoms they cause could be the result of other common problems such as herbicide injury, pH or nutrient deficiencies.”

Further complicating the issue is that above-ground symptoms may not be visible, which results in significant yield losses.

Root lesion nematode can be troublesome because it has a wide host range with substantial economic impact. In 2009, a limited survey of 90 fields from Windsor to Toronto found 38 per cent of samples were considered above root lesion thresholds established in the United States.

Ontario thresholds for root lesion and other nematodes in field, horticultural and other crops have yet to be developed and will be a metric of this project.

Since many nematode species can infect and injure multiple crops, the distribution and population data obtained from this survey will relate to many Ontario crops.

“Nematode activity often goes unnoticed but they can often produce many openings or wounds on the roots,” says Tenuta.

“This allows secondary plant pathogens (like root rot organisms) easy access to the roots, resulting in additional plant health issues such as shallow or weak root systems with increased browning. They’re also prone to further environmental stress.”

Options to manage nematodes are limited and although there are new seed treatment nematicides, there aren’t any silver bullets. Preventive measures are key.

Crop rotation has limited effect against certain nematodes, including root lesion nematode, because of the pest’s many potential hosts.

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