SCN Makes Crops More Susceptible to SDS

Soybean cyst nematode (SCN) is a devastating and yield-limiting pest of the soybean worldwide. Syngenta, as a pioneer in controlling this pathogen, offers their second SCN Education Series to help educate growers and retailers on the best practices for reducing damage and increasing soybean yields. Clariva Complete Beans seed treatment from Syngenta includes a revolutionary ingredient with a unique, direct mode of action that is lethal to soybean cyst nematodes, delivering immediate and long-lasting protection of plant root systems resulting in significant yield benefits.

For decades, soybean cyst nematode (SCN) has been a problem in U.S. soybean fields and worldwide. But recently, researchers have found a clear connection between it and another yield robber. Couple SCN with sudden death syndrome (SDS), and crop damage multiplies.

The relationship has been suspected for a long time, says Dr. Jamal Faghihi, research and extension nematologist with Purdue University. The evidence just wasn’t “concrete.” That changed in 2010 when he conducted trials that showed any place where resistance to SCN broke down, SDS symptoms were more severe. Four years of subsequent studies on the same site have shown close to identical results.

In 2013, Faghihi and his team created a time lapse video of their trial plot spanning a month and a half. It shows the progress of SCN damage coupled with SDS infestation (http://extension.entm.purdue.edu/pestcrop/2013/issue24/index.html). He calls the footage eye-opening and, according to Faghihi, has received “huge feedback from growers and others who have seen it. They are convinced as well that there is a direct correlation.”

Faghihi says the heart of the problem is the breakdown of resistance to SCN that’s formerly been virtually guaranteed by the industry staple genetics, PI88788, contained in more than 95 percent of commercial varieties. That failure (which allows some nematode feeding and root damage) stresses the plants and allows or enables severe SDS damage. In fact, other stresses such as soil compaction and fertility problems also encourage SDS.

“We tend to see more SDS symptoms now because SCN resistance is breaking down,” he summarizes.

Dual Management Approach
When both problems are present in the same field, they need to be managed simultaneously, Faghihi says. His first recommendation to growers is to see what the SCN population is like in their fields. Soil samples — taken any time of year, even the dead of winter — are the key. He suggests one sample for every 10 acres, though other state extension experts say a larger area can work as well.

“I think some growers are dropping the ball on SCN by not sampling,” says Faghihi. In fact, he’s seen samples coming into Purdue drop from 4,000-5,000 to just 400-500 in the last few years.

Dr. Kiersten Wise, associate professor of plant pathology at Purdue, joined Faghihi in his work on the SCN/SDS trials. She is evaluating other tactics, including varied planting dates and fungicide seed treatments. She says preventative measures before planting are very important, since – like SCN – there are no options for managing the disease during the season.

“Although genetic resistance to SCN may not be as effective as it once was, it remains a key tool for managing both SCN and SDS; it remains the growers’ number one most effective tool and the place all SCN management programs should begin,” says Dale Ireland, Seedcare technical product lead with Syngenta. Additionally, when looking to reduce SDS impact, genetic resistance is readily available and especially strong within the NK® Soybeans lineup. Again, SDS genetic resistance is foundational in any SDS management system

Other Options
Unfortunately, SCN resistance problems have been happening more and more often. However, there is hope in the form of Clariva® Complete Beans seed treatment from Syngenta. Clariva Complete Beans provides direct activity on SCN and lethal, season-long protection that enhances SCN-resistant varieties. By killing this nematode, growers are also able to better protect their fields from SCN-related diseases, such as SDS. Growers struggling with SDS are also recommended to use Mertect® 340-F fungicide for proven, effective SDS protection. Providing growers with an additional form of protection against SCN on top of SCN-resistant seed varieties is crucial in the fight against the spread of this nematode.

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