Not all SCN-resistant soybean varieties control SCN equally. And there is no legal definition or industry standard of SCN control required for a variety to be call SCN-resistant. Similarly, there are nematode-protectant seed treatments for sale to Iowa farmers, but no minimum level of control of SCN required. The field experiments we propose will provide data from nine different locations throughout Iowa on the effects of SCN-resistant soybean varieties and nematode-protectant seed treatments on SCN reproduction and soybean yields.
This project addresses "soybean disease, nematode, insect pest and abiotic stress biology, managment and yield loss mitigation," a stated key area of research and outreach focus for the ISA. A total of 36 different field experiments (4 different studies in each of Iowa's 9 crop-reporting districts) will be conducted in the 2024 growing season to determine the effectiveness of SCN-resistant soybean varieties and nematode-protectant seed treatments. A comprehensive, multi-faceted communication effort will disseminate research results in print and electronic media and in ag media interviews and presentations to Iowa soybean farmers.

There are three objectives to achieve the overall project goal, namely to assess and study:
1) the agronomic performance and nematode control provided by SCN-resistant soybean varieties marketed to Iowa soybean farmers
2) the effects of increasing SCN reproduction on yields of SCN-resistant soybean varieties
3) the effects of nematode-protectant seed treatments on agronomic performance and reproduction of SCN on resistant soybean varieties

Deliverables and Outcomes:
* an annually updated list of SCN-resistant soybean varieties for Iowa farmers (ISU Extension publication PM-1649)
* an annually updated report of results of resistant variety trial experiments (ISU Extension publication IPM-52) - printed and distributed as an insert in the Iowa Farmer Today magazine
* research articles published in scientific journals such as Plant Disease and Plant Health Progress

Update:
In the last 6 months (1 October 2023 through 31 March 2024) we:
- compiled and prepared a publication titled “Soybean cyst nematode-resistant soybean varieties for Iowa,” posted online in November 2023 - see https://doi.org/10.37578/ONKA5947; a PDF file of the publication is attached here also.
- harvested plots in all 9 SCN-resistant variety trial experiments and 27 seed treatment evaluation experiments to determine yields in October 2023
- collected soil samples from every plot the variety trial and seed treatment experiments at the time of harvest to determine final SCN soil population densities in October 2023
- extracted SCN cysts, then eggs, from 3,240 soil samples collected from the SCN-resistant variety trial and seed treatment experiments at harvest, then counted the eggs to determine final SCN egg population densities from November 2023 through March 2024
- compiled and analyzed yield and SCN population density data from the SCN-resistant variety trial and seed treatment experiments in December 2023
- prepared a printed report of the SCN-resistant soybean variety evaluation experiment results, printed the report, and then had the report distributed to 48,000 Iowans as a special insert in the January 12, 2024, issue of the Iowa Farmer Today newspaper - the report is available online - see https://doi.org/10.37578/UDSP9793 and a PDF file of the publication is attached here also.
- published two articles in the ISU Integrated Crop Management Newsletter about the resistant variety list and the variety trial results:
• Tylka, G. 2023. Fall is Prime Time to Sample Fields for SCN. Iowa State University Integrated Crop Management News (6 October 2023). https://crops.extension.iastate.edu/cropnews/2023/11/fall-prime-time-sample-fields-scn
• Tylka, G. 2023. New Data-Based Calculator Estimates Economic Yield Loss from SCN in Individual Fields. Iowa State University Integrated Crop Management News (10 November 2023). https://crops.extension.iastate.edu/cropnews/2023/11/new-data-based-calculator-estimates-economic-yield-loss-scn-individual-fields
• Tylka, G. 2023. Updated SCN-resistant Soybean Variety List Has More with Peking Resistance than Ever. (20 November 2023) https://crops.extension.iastate.edu/cropnews/2023/11/updated-scn-resistant-soybean-variety-list-has-more-peking-resistance-ever
• Tylka, G. 2023. Quick Guide to Soybean Varieties for Iowa with Peking SCN Resistance. (28 November 2023) https://crops.extension.iastate.edu/cropnews/2023/11/quick-guide-soybean-varieties-iowa-peking-scn-resistance

- began contacting seed companies to request seeds of SCN-resistant soybean varieties for 2024 field experiments in January-February 2024
- contacted BASF, FMC, and Syngenta personnel for seeds treated with Ilevo, Avodigen, and Saltro, respectively, for 2024 small-plot field experiments
- began receiving seed from seed and seed-treatment companies for 2024 field experiments, and designed the 2024 field experiments and began packaging of seeds for the various experiments in March 2024
- received 88 Peking varieties to include in variety evaluation experiments in 2024, which is up from 62 such varieties in 2023
- conducted final soil sampling of farmer fields throughout Iowa to allow for selection of the 2024 experimental field locations in March 2024

View uploaded report

View uploaded report 2

Updated October 16, 2024:
Project progress from 1 April 2024 through 30 September 2024 included:
- Received seed from seed and seed-treatment companies for field experiments in 2024, designed the 2024 field experiments, and packaged and organized the seeds for the various experiments. Varieties from 34 brands were studied in the 2024 SCN-resistant soybean variety trial experiments are as follows: AgriGold, Asgrow, Beck, Champion, Channel, Connect, Cornelius, Credenz, Dyna-Gro, Four Star Seed Co., FS HISOY, Golden Harvest, Hoegemeyer, Impact, Innotech, Jacobsen, Kruger, Latham, Legacy Seeds, Legend, LG Seeds, Loyal Brand, Merschman, Mustang, NK, Nutech, P3 Genetics, Pioneer, Rob-See-Co, Stine, Sunrise, Titan Pro, Xitavo, and Zinesto.

- Most of the varieties tested in the 2024 variety trial experiments possessed SCN resistance from PI 88788, but the following 22 brands had varieties with Peking SCN resistance in the experiments: Agrigold, Apex, Beck, Champion Seed, Connect, Dyna-Gro, FS HISOY, Golden Harvest, Hoegemeyer Hybrids, Hefty, Latham, LG Seeds, Merschman, Mustang, NK, Nutech, Pioneer, P3 Genetics, Stine, Titan Pro, Xitavo, and Zinesto.

- Set up, planted, soil sampled, maintained, and prepared to harvest nine field experiments located throughout Iowa to evaluate the yield enhancement and nematode control provided by 196 different SCN-resistant soybean varieties in 2024.

- Set up, planted, soil sampled, maintained, and prepared to harvest nine field experiments located throughout Iowa to evaluate the agronomic performance and nematode control provided by three different nematode-protectant seed treatments, namely Ilevo (from BASF), Saltro (from Syngenta), and Avodigen (from FMC).

- Extracted SCN cysts (egg-filled dead SCN females), then eggs, from soil samples collected at planting from all 9 resistant variety evaluation experiments and the 27 seed treatment experiments and counted the eggs to determine initial SCN egg population densities.

- In early September, the field research plots at the 36 total field experiments were end-trimmed in preparation for harvesting, which was completed in October 2024.

- In August 2024, we contacted 60 seed companies and gathered information about SCN-resistant soybean varieties to use to update the ISU Extension publication titled “Soybean Cyst Nematode-Resistant Soybean Varieties for Iowa”. This publication has just been finalized and will be released in PDF format by the end of October 2024.

SCN is estimated to be present in 70% to 75% of the fields in Iowa. Currently there are three options for managing SCN: 1) growing nonhost crops such as corn, 2) growing SCN-resistant soybean varieties, and 3) using nematode-protectant seed treatments on soybean seeds. The results of the field experiments conducted in this project help Iowa soybean farmers decide which resistant varieties and seed treatments to purchase for use in fields infested with SCN. The results of the experiments conducted in 2024 are not yet available because all the end-of-season (harvest) SCN soil samples have not been processed and counted. However, all work on the 2024 experiments will be completed by the end of calendar year, after which planning for 2025 will commence. The report of 2023 variety trial experimental results and the 2023 list of SCN-resistant soybean varieties for Iowa are available online at https://doi.org/10.37578/UDSP9793 and https://doi.org/10.37578/ONKA5947, respectively .

The overall goal of this project is to provide Iowa soybean farmers with research-based information about resistant varieties and seed treatments for managing SCN.