loss caused by nematodes,” he says. When Tylka teaches SCN management, he compares managing it to that of high blood pressure. “Anyone with high blood pressure knows there is not one single pill to control their condition,” Tylka says. “In addition to medication, there are also all sorts of behavioral changes that work together to manage this chronic health problem.” The first step to manage SCN is to take a soil test to assess the density of SCN infestation. Growers are often unaware they have a problem. Growing a resistant variety is the prescribed pill. The other critical thing is to rotate resist- ant varieties. This is difficult because there are not many alternatives. Tylka says research- ers hope this will change as breeders become more successful in developing high- yielding varieties with new sources of resistance. Crop rotation with a nonhost crop such as corn, oats or alfalfa is one of the behavioral changes needed to control SCN. The SCN Coalition reports the largest decline in SCN numbers occurs following the first season a nonhost crop is grown. Seed treatments should also be considered. Seed treatments can help reduce SCN reproduction and/or increase soybean yields in SCN infested fields or they may have no effect. Results vary among the differ- ent seed treatment products, between growing seasons and soil environments. “At this point nobody can tell a farmer at the beginning of the season when or where a particular product will or will not work,” Tylka says. ”That is the nature of biology. We thought we had a home run back in the 1990s with PI 88788 but times change and nature overcomes. Nature is the ultimate arbitrator.” Using cover crops to manage SCN is a new con- cept. Work coming out of Europe indicates cover crops could reduce nematode num- bers. As such, several U.S. uni- versities are studying the role of cover crops and looking at why some do, and others do not, affect SCN populations. “In one field, a crop of annual rye, for example, might reduce SCN numbers while having no effect in another field,” Tylka says. “There is much interest in cover crops and SCN.” Simply put, the more measures a farmer uses to control SCN or any pest, the less likely any individual management tactic is going to suffer decreased perfor- mance. Future Prospects In February 2019, Iowa State University researchers pub- lished the fully assembled SCN genome, which could lead to the development of better pest management strategies. “The soybean cyst nema- tode genome sequence reveals a diversity of mecha- nisms that give rise to viru- lence genes,” says lead author Thomas Baum, an Iowa State University professor and chair of plant pathology and microbiology. “It provides new insights into the SCN’s biol- ogy and sheds light onto the mystery underlying complex host-parasite interactions.“ Funding for the research was provided by the North Central Soybean Research Program (NCSRP) with money from the soybean checkoff and the National Science Foundation Center for Arthropod Management Technologies and its industry partners. The NCSRP in collabo- ration with the University of Missouri, the University of Illinois and Iowa State University is in the fourth year of a multi-year project to develop an integrated approach to enhance the durability of SCN resistance for long term strategic SCN management. The new SCN genome will provide criti- cal information in the team’s efforts to develop new soybean varieties with SCN resistance. “The widespread lack of genetic diversity in SCN resistance in soybean has sig- nificantly reduced the effec- tiveness of current sources of resistance,” says Melissa Mitchum, project leader and a molecular nematologist at the University of Missouri. “We have two major research challenges that, when suc- cessfully achieved, will enable us to develop more efficient JUNE 2019 SEEDWORLD.COM / 57 Melissa Mitchum is a molecular nematologist in the Division of Plant Sciences and Bond Life Sciences Center at the University of Missouri.