What is "soybean cyst nematode"

The soybean cyst nematode (SCN), Heterodera glycines, is a plant-parasitic nematode and a devastating pest of the soybean (Glycine max) worldwide. The nematode infects the roots of soybean, and the female nematode eventually becomes a cyst. Infection causes various symptoms that may include chlorosis of the leaves and stems, root necrosis, loss in seed yield and suppression of root and shoot growth. SCN has threatened the U.S. crop since the 1950s, reducing returns to soybean producers by $500 million each year and reducing yields by as much as 75 percent. It is also a significant problem in the soybean growing areas of South America and Asia.