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ILeVO (fluopyram) is a fungicide seed treatment for soybean sudden death syndrome (SDS) that also has nematicidal activity. ILeVO is sold with a base of insecticide Poncho (clothianidin), nematode-protectant VOTiVO (Bacillus firmus), and Acceleron fungicides (metalaxyl, fluxapyroxad, and pyraclostrobin). Yield and reproduction of the soybean cyst nematode (SCN) (Heterodera glycines) on soybean plants grown from seed treated with ILeVO plus the base were compared with those treated with only the base in 27 small-plot experiments and 12 strip-trial experiments across Iowa from 2015 to 2017. To increase the likelihood that yield results were related to effects on SCN, data were used only from 26 small-plot experiments and 12 strip trials in which symptoms of SDS were low or nonexistent. An SCN reproductive factor (RF) was calculated for each experimental unit by dividing the SCN population density at harvest by the population density at planting. ILeVO significantly reduced SCN RF by 50% in one strip-trial experiment and by 36 to 60% in four small-plot experiments but yields were not increased by ILeVO in any of those five experiments. Soybean yields were 2.8 to 3.7 bushels/acre (bu/ac) (188.3 to 248.8 kg/ha) greater with ILeVO in three small-plot experiments but SCN RF was not reduced in those experiments. Also, yield was 1.9 bu/ac (127.8 kg/ha) greater with ILeVO in one strip-trial experiment in 2016 but SCN samples were not collected at harvest from the study to assess the possible effects of ILeVO on SCN reproduction. When strip-trial data from 2015 and 2016 were combined, there was a small but significant 0.8 bu/ac (52.2 kg/ha) yield increase with ILeVO. Overall, the effects of ILeVO on SCN reproduction and soybean yield were variable in these field studies.

In the United States and Canada, the most damaging pathogen of soybean, Glycine max, is the soybean cyst nematode (SCN), Heterodera glycines. Plant health professionals working for universities and state and provincial departments of agriculture in the United States and Canada are queried periodically about counties and rural municipalities that are newly known to be infested with SCN in their states and provinces. Such a census was conducted in 2020, and the results were compared with results of the most recent survey, published in 2017. Between 2017 and 2020, 55 new SCN-infested counties were reported from 11 U.S. states. Also, 24 new SCN-infested counties and rural municipalities were identified in the Canadian provinces of Manitoba, Ontario, and Quebec. A map of the known distribution of SCN in these two countries was updated. The results reveal steady expansion of the distribution of SCN throughout the United States and Canada, and the pest almost certainly will continue to spread among and within soybean-producing areas of these countries in the future. Therefore, continued scouting and soil sampling for detection of new SCN infestations are warranted as the first step toward successfully managing the pathogen.

ILeVO (fluopyram) is a fungicide seed treatment for soybean sudden death syndrome (SDS) that also has nematicidal activity. ILeVO is sold with a base of insecticide Poncho (clothianidin), nematode-protectant VOTiVO (

In recent years, nematode-protectant seed treatments have become available to supplement resistant soybean cultivars to manage soybean cyst nematode (Heterodera glycines; SCN). Twenty-seven small-plot and 18 strip-trial experiments were conducted comparing the effects of Clariva Complete Beans (CCB) and CruiserMaxx Advanced plus Vibrance (CMV) on SCN reproduction and soybean yield on a moderately resistant (2014) and resistant (2015 to 2016) soybean cultivar. Yield data were collected, and an SCN reproductive factor was calculated by dividing final (at harvest) SCN egg population densities by initial (at planting) population densities from soil samples collected in each small plot or sampled area in the strip trials. Relative to the CMV treatment, CCB significantly decreased SCN reproductive factor in two small-plot experiments (one each in 2014 and 2015) but not in any of the strip trials in any year. Soybean yields were significantly greater with CCB versus CMV in 5 of the 18 strip trials but not in any of the small-plot experiments, even when there were significant decreases in SCN reproduction. For unknown reasons, CCB significantly decreased yields in two small-plot experiments and at one strip-trial location. In summary, the effects of CCB seed treatment on SCN reproduction and soybean yields were variable in the years that these experiments were conducted in Iowa.

Management of the soybean cyst nematode (SCN) relies heavily on use of SCN-resistant soybean varieties to limit nematode reproduction and minimize yield loss. For Iowa, almost all SCN-resistant soybean varieties contain SCN resistance genes from a breeding line named Plant Introduction (PI) 88788. Iowa State University conducts experiments to evaluate numerous SCN-resistant and three to four SCN-susceptible soybean varieties in up to nine field experiments across Iowa each year. Data on SCN population density, virulence (SCN race and HG type), soybean yield, precipitation, and growing degree days from more than 25,000 four-row plots in field experiments conducted from 2001 to 2015 were analyzed to determine how these factors affected SCN reproduction and yield. SCN population densities were positively correlated with temperatures and negatively associated with precipitation during the growing seasons, indicating that SCN reproduction was greatest in hot, dry years. Over the years, virulence of SCN populations on PI 88788 increased in the fields in which the experiments were conducted, resulting in increased end-of-season SCN population densities and reduced yields of SCN-resistant soybean varieties with the PI 88788 source of resistance. These results indicate that soybean yield loss caused by SCN on resistant varieties with the common PI 88788 source of resistance likely will increase as virulence of SCN populations increases unless new sources of resistance become widely available and used in the future.

The objective of this study was to determine how HG type test results might vary among SCN populations in independent samples collected from the same field or area of a field. Accepted for publication 20 June 2016. Published 22 July 2016.

The soybean cyst nematode (Heterodera glycines) is considered the most damaging pathogen of soybean in the USA and Canada, and causes considerable yield loss in many other soybean-producing countries. It is believed to have been introduced into North America from Asia. The map of the known distribution of H. glycines in the USA and Canada has been updated for 2014. Maps of its known distribution in past years illustrate the spread of the pathogen since its initial discovery in the United States in 1954. Accepted for publication 20 April 2014. Published 27 May 2014.

The soybean cyst nematode (SCN) is a major yield-reducing pathogen of soybeans in North America. The nematode is an introduced pest and, therefore, knowledge of the distribution of SCN can be helpful in identifying areas where scouting and management efforts should be focused. Such information is especially important because yield-reducing infestations of SCN can occur without obvious above-ground symptoms appearing. In late 2016, nematologists, plant pathologists, and state plant regulatory officials from the soybean-producing states in the United States and provinces in Canada were queried to obtain the latest information on where the nematode had been found. An updated map of the known distribution of SCN in North America was also created. There were 17 states in which SCN was newly found since 2014, when the map was last updated, including the first discovery of SCN in the state of New York. North Dakota was the state with the greatest number of counties, seven, in which SCN had been newly discovered since 2014. This updated information illustrates that the nematode continues to spread throughout the soybean-growing areas of the continent and emphasizes that continued efforts to scout for and manage SCN are warranted.

Field experiments were conducted at locations in northern and southern Illinois, central Iowa, and central Missouri from 1997 to 1999 to investigate the effects of Heterodera glycines on soybean growth, development, and yield. A wide range of infestation levels was present at all locations. Two locally adapted cultivars, one resistant to H. glycines, were grown at each location. Cultivars were planted in alternating four-row strips with 76 cm between rows. For each cultivar, 20 1-m-long single-row plots were sampled every 2 weeks starting 4 weeks after planting. Infection by H. glycines reduced plant height and leaf and stem weight on the resistant cultivars in the first 12 weeks after planting, and delayed pod and seed development 12 to 14 weeks after planting. Biomass accumulation was not reduced on the susceptible cultivars until 10 weeks after planting; reduction in pod and seed development occurred throughout the reproductive stages. Susceptible cultivars produced significantly lower yields than resistant cultivars, but the yield reductions were not accompanied by visually detectable symptoms.

Introduction Use of resistant soybean varieties is a very effective strategy for managing soybean cyst nematode (SCN), and numerous SCN-resistant soybean varieties are available for Iowa soybean growers. Each year, public and private SCN-resistant soybean varieties are evaluated in SCN-infested fields in Iowa by Iowa State University personnel. The research described in this report was performed to assess the agronomic performance of SCNresistant soybean varieties and to determine the effects of the varieties on SCN numbers or population densities.

Introduction The use of resistant soybean varieties is a very effective strategy for managing soybean cyst nematode (SCN), and numerous SCN-resistant soybean varieties are available for Iowa soybean growers. Each year, public and private SCNresistant soybean varieties are evaluated in SCNinfested and noninfested fields throughout Iowa by Iowa State University personnel. The research described in this report was performed to assess the agronomic performance of maturity groups (MG) II and III SCN-resistant soybean varieties and to determine the effects of the varieties on SCN population densities.