Mystery Solved

Imagine a grower who plants a high-yielding soybean variety into a weed-free field, cleaner than his grandmother's kitchen. He doesn't allow a single weed to grow beyond 2 inches throughout the season, preemptively applies a fungicide to maximize plant physiological benefits and has minimal problems with insect feeding. He's even fortunate enough to have highly productive, well-drained loamy soil. But despite his steadfast efforts, he can't seem to break 52 bushels per acre. So what happened?

Chances are high that his fields are infested with soybean cyst nematodes (SCN). Fields infested with SCN often exhibit minimal above-ground symptoms, but the microscopic soilborne culprit still has the ability to decimate soybean yields by feeding on roots. In fact, it is responsible for the loss of approximately 120 million bushels of soybeans per year in the U.S. alone, according to scientists at the University of Missouri, and costs U.S. growers $1.5 billion annually. This translates into as much loss in American-grown soybeans as the next four most damaging soybean pests combined.

A Winning Combination

Fortunately, growers will have a new weapon in the fight against this destructive pest for the 2014 growing season - Clariva^™ Complete Beans, a new seed treatment combination of separately registered products that adds revolutionary protection against SCN to the market-leading fungicide/insecticide mixture of CruiserMaxx^® Beans with Vibrance^®.

This seed treatment combination will offer season-long activity against SCN while protecting soybean crops against early-season insects and diseases. It also will help improve root health, delivering better emergence, stand, stress tolerance and overall performance.

Pasteuria nishizawae, the active ingredient in Clariva Complete Beans, is a proven natural enemy to SCN. Ironically, it feeds off SCN, just as its host feeds off a soybean plant. In essence, Pasteuria nishizawae is a parasite of a parasite of soybean. Its spores latch onto the nematodes. Instead of swelling with eggs, the infected SCN now fills up with spores. Similar to an over-inflated balloon, the SCN expands beyond its limits and dies.

"By manufacturing a seed-applied Pasteuria nishizawae, our company can offer a technology that works from day one, all season long," says André Oliveira, global senior business manager at Syngenta. "Pasteuria nishizawae is an aggressive parasite of SCN. Through its unique mode-of-action, it reduces feeding and reproduction, ultimately killing the pest.

Nematology 101

The first U.S. documented case of SCN dates back to 1954 in Hanover County, N.C. SCN has since spread across the country and now covers much of the Midwest.

"One cyst, composed of hundreds of eggs, is about the size of a period at the end of a printed sentence," says Greg Tylka, Ph.D., professor and nematologist at Iowa State University. "It can easily be contained in a soil particle, so anything that moves soil is going to have the potential to move SCN, including wind, farm machinery and even wildlife."

When temperatures and moisture levels are adequate in the spring, worm-shaped juveniles hatch from the egg into the soil. The soybean roots act as beacons for food to these young juvenile nematodes, which have no problem finding a point of entry and forming their feeding site inside the root. This feeding site, known as the syncytium, opens an entryway for other pathogens and increases the soybean plant's susceptibility to a number of soilborne pathogens, such as Pythium, Rhizoctonia, Phytophthora and Fusarium - particularly one Fusarium species in the Midwest that causes sudden death syndrome.

"The syncytium is going to make the root less able to move water and nutrients throughout the plant," says Tylka. "It stunts the root system to diminish the plant's functionality."

During the later juvenile stages when the young nematode is growing inside the root, the SCN molts-a shedding process that allows it to grow-to either become an adult male or female. The adult male exits the plant; the adult female, however, continues feeding on the soybean root. After mating, she produces hundreds of eggs and grows larger. Once the female SCN dies, her body hardens to create a protective case around the eggs. The naked eye can now easily identify the female body case as a cyst on the root, and the lifecycle starts again. This process only requires 24 to 30 days under ideal conditions, accounting for the exponential growth in SCN population.

Rotation Requirements

When it comes to minimizing damage, growers must first understand the gravity of SCN in a field so they can more accurately diagnose what treatment options may be required.

Rotation is a key component in any nematode management plan. Although SCN-resistant varieties work well to combat the pest, the overuse of a single source of resistance-SCN resistant varieties currently on the market only use seven different genetic sources-has often led to reduced efficacy. It's also important for growers to practice seasonal rotations to non-host crops. Rotational crops, such as corn, diminish the SCN population in a field. Without a source of food, any SCN eggs that hatch will die.

"Clariva Complete Beans boosts agronomic practices that defend against SCN damage," says Wouter Berkhout, Syngenta product lead for soybean seed treatments. "It also helps protect high-value seeds in managing resistance."

A Major Step Forward

Until recently, Pasteuria nishizawae could only be grown in vivo, meaning that it required a living host. However, through entrepreneurial and scientific innovation, Pasteuria Bioscience Inc., a company Syngenta recently acquired, mastered the art of reproducing Pasteuria spores in vitro (meaning outside a living organism). By removing the need for a living host during the spore's reproduction, Syngenta has the ability to produce on a commercial scale a natural enemy of SCN contained in a convenient combination of seed treatments - Clariva Complete Beans.

"We've developed this product in response to a growing need to control SCN, and it is a fantastic solution used in a program that includes SCN-resistant varieties," says Berkhout. "After implementing multiyear field trials, we're confident this program approach will deliver a strong return on investment for growers fighting SCN." By improving soybean performance in SCN-infested fields across the Midwest, Clariva Complete Beans will offer growers the missing piece to this billion-dollar puzzle. And solving one of the costliest problems of soybean agriculture can only mean one thing for growers: increased yield potential.