Suppressing NematodesIn Michigan Sugarbeets

Above: Fairgrove, Mich., grower Mark Sylvester planted this 2013 oilseed radish trap crop on July 25 following the field’s pickle harvest, with this photo taken September 21. The field goes into sugarbeets in 2014.

Tolerant Varieties, Oilseed Radish Cover Crop & Extended Rotation Comprise Sylvester Plan
Sugarbeet cyst nematode (SBCN) has been around the Michigan and Ontario growing region for a long time. It was first discovered in Ontario in the 1930s, and initial reports in Michigan beets date back to the latter 1940s. As of the mid-2000s, a random field survey conducted by Michigan State University (MSU) and Michigan Sugar Company (MSC) personnel found detectable levels of SBCN in 22% of Michigan’s sugarbeet fields. A 2012 MSC survey found it in 24% of fields sampled.

“Research has shown that heavy infestations can reduce yields by as much as 15 tons per acre and 2.2% in sucrose,” notes Steve Poindexter, MSU extension sugarbeet specialist. 

“Moderate nematode pressure has shown an average loss of 3.3 tons per acre and over 0.5% in sucrose.” Low SBCN populations can affect yield even though there may not be any visual symptoms of infestation, he adds.

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Michigan beet growers have fought back against the nematode with longer rotations, the planting of cover crops — and, more recently, with nematode-tolerant varieties. Poindexter says about half of Michigan’s 2013 beet acreage was planted to nematode-tolerant varieties. Four such varieties were on the market in the region last year: two from Betaseed (B-19RR1N and B-18RR4N), one from ACH Seeds (C-RR074NT) and one from Seedex (SX-1211NRR). New for 2014 are Betaseed’s B-12RR4N and Syngenta/Hilleshog’s HM-NT425RR, with more nematode-tolerant varieties likely coming into the market by 2015.

The oilseed radish root attracts sugarbeet cyst nematodes but then interrupts their reproduction, reducing populations by up to 80-90%. ‘Tillage’ radishes, though, are excellent hosts for nematodes and should never be used as a trap crop.

* It’s very important to remember there
are two different kinds of oilseed radish:
a ‘nematode trap’ radish and a ‘tillage’
radish, MSU’s Steve Poindexter emphasizes.
“If growers plant the tillage
radish in a nematode field, it will actually
increase nematode populations.
The nematode trap crop radish has
some different genetics that cause the
nematode to hatch, go to the root — but
not reproduce. So it actually lowers
population,” he points out.

Like many other Michigan growers, Mark Sylvester of Fairgrove regularly plants nematode-tolerant varieties on at least part of his beet acreage. And like a number of others, he also counts on oilseed radishes* to help suppress nematodes (by interrupting their reproductive system) while simultaneously contributing to soil health.

On Sylvester Farms (operated by Mark and his parents, Rich and Nancy), those radishes typically are seeded intojust-harvested pickle ground intended to go into beets the following year. (Sylvester also seeds clover for cover crop into yet-dormant winter wheat in early spring, i.e., “frost seeding.”)

Though Sylvester always has been aware of the potential yield loss from nematodes, the benefits of an oilseed radish cover crop, coupled with a tolerant variety, were dramatically displayed in 2006. Prior to then, the top beet yield on one longtime Sylvester field had been 17 tons per acre — mainly due to nematodes. That field was last planted to beets in 2002. The Sylvesters seeded two oilseed radish crops in the interval until the next beet crop in 2006, when they likewise
planted a nematode-tolerant variety on part of the field. Those beets ended up yielding 34 tons per acre — twice that
of the previous best on that field. “Even the non-tolerant variety (planted on the other field portion) went 29 tons,” Mark recalls by way of underscoring the value of oilseed radishes. 

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In more heavily infested fields, the Sylvester approach includes both 
a radish crop and a nematode-tolerant variety.

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2013 was the 11th year in which the Sylvesters seeded oilseed radishes on upcoming beet ground. The initial time — 2003 — likewise was their second year of growing pickles. Since then, their standard regimen has been to harvest the pickles in late July, run a ripper across the field to break up some compaction — and then seed about 15 pounds per acre of oilseed radish with a no-till drill. They’ll usually work down the radishes in mid-October.

The cost of the radish seed (“Defender” is the variety they use) and its planting pass constitute the only inputs. “We do not put any more fertilizer on” with the radishes, Sylvester notes. “If we were to plant radishes after wheat, we’d probably need to add some nitrogen. But there’s always some [nitrogen] left over after the pickle crop.” He does spread two tons of lime; but the lime goes on all their upcoming beet ground, so it’s not expensed to the cover crop specifically.

The Sylvester currently plant nematode- tolerant varieties on about half their sugarbeet acreage. Soil bioassays of nematode populations influence that decision, as does the presence of the oilseed radish cover crop. Closer to the home farm, with its longer history of sugarbeets, “I usually plant nematodetolerant varieties,” Mark says. “But I don’t necessarily use a tolerant variety where I’ve just had a radish cover.” In more-heavily infested fields, however, the approach includes both a radish crop and a nematode-tolerant variety.

An extended rotation is another key component in the Sylvester nematodefighting toolkit. They aim for a five year rotation. “We feel that gives us an advantage when we do come back with the beets,” Mark says. — Don Lilleboe


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