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Adult SCN females infest soybean roots
TIME TO TEST: Adult SCN females infest soybean roots. Sample soil this fall, have it tested, know what the SCN population is in your fields.

SCN populations increasing

Elevated SCN pressure calls for an integrated management approach.

A recent report from Greg Tylka, plant pathologist at Iowa State University, suggests that soybean cyst nematode reproduction was accelerated in Iowa this year. Tylka believes this was due to the consistently warm temperatures that occurred in parts of Iowa from May through July.

Once SCN is found in a field, they can’t be eliminated. That’s why Tylka says it’s necessary to take an integrated approach to SCN prevention and management.

“An integrated approach means using several different management tactics in a coordinated effort to manage SCN,” Tylka says. “This approach is important to reduce the chances of SCN overcoming any single management tactic, and it broadens the overall chances of successful management of the nematode.”

Know your numbers
Following a 20-year hiatus, the SCN Coalition was resurrected earlier this year to increase much needed awareness about the growing threat of SCN. The coalition has been stressing how SCN is adapting to SCN-resistant soybean varieties. And now, many growers are seeing their yields decrease.

With this growing concern, the coalition’s principle to “know your numbers” is emphasized. That’s why Syngenta became a partner in this initiative earlier this year. Joining with university researchers, the company has stressed the need for accurate SCN diagnosis and appropriate treatment.

Being aware of the pressures that lay within your fields is the first step toward effective management. And soil sampling is the only way to determine this, Tylka says. Luckily, it’s an inexpensive, simple task, he adds.

Test your soils in timely manner
“Postharvest is the best time to test your soils for SCN because you’ll get the most accurate read before fields begin to freeze,” says Randy Kool, Syngenta agronomy service representative based at Adel in central Iowa. “Soil sampling in the winter can be difficult, and waiting until spring to sample the soil won’t leave you much time to come up with an effective management plan.”

When collecting your regular fall soil fertility samples, it’s easy enough to split them into two: use one sample to test for SCN and the other one to test soil fertility. If you haven’t already sampled your soils, you may want to consider adding it to your to-do list this month before winter begins.

Plant SCN-resistant soybean varieties
Planting SCN-resistant varieties is an important practice for managing SCN. However, it’s not a silver bullet. According to the SCN Coalition, and backed by research from multiple universities, SCN is becoming resistant to the PI 88788 source of resistance, currently used in more than 90% of SCN-resistant soybean varieties.

“The effectiveness of the most common resistant soybean varieties available on the market today are being overcome by SCN populations in fields throughout the Midwest,” Tylka says.

Managing SCN has become much more complex than simply planting an SCN-resistant variety and looking in the other direction. That’s why this practice should be considered in conjunction with other management practices.

Choose effective seed treatment
“Using nematode-protectant seed treatments can help bolster the eroding effectiveness of SCN-resistant soybean varieties,” Tylka notes. So, when choosing a seed treatment, it’s important to do your research and ensure you’re choosing the most effective option for your farming operation.

“Unlike the other seed treatments available, the Clariva Elite Beans seed treatment provides season-long activity against SCN,” Kool says. “It’s an easy-to-handle premix of Clariva “pn” nematicide and CruiserMaxx Vibrance seed treatment, designed to enhance the performance of SCN-resistant varieties that have the PI 88788 resistance source. Since SCN can have up to six generations per season, the extended length of control that Clariva Elite Beans provide is necessary for the best possible protection against SCN.”

Consider crop rotation
Rotating infested fields with a nonhost crop will help disrupt SCN’s life cycle, making it difficult for this pest to reproduce, Tylka says. The practice of rotating soybean fields with corn or another nonhost crop, such as a small-grain crop, will help prevent SCN from becoming an even bigger issue down the road.

Sources: Iowa State University, Syngenta

TAGS: Crop Disease
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