The use of seed treatments on soybean has increased dramatically within the past decade with approximately 90 percent of seed treated in 2013. Concerns have been raised regarding the development of fungicide resistance in seedling pathogens, and the use of neonicotinoids in soybean, which is attractive to pollinators.This project evaluates commercial seed treatments in small plot trials and in collaboration with the ISA On-Farm Network, and monitors fungicide sensitivity in seedling pathogens. Consequently the data extend the current state of knowledge of seed treatments on soybean that reduce early insect damage and disease.

1. Compare the effect of commercial seed treatments on seedling disease, soybean cyst nematode, insect pests, and yield potential in small plot trials at multiple locations in Iowa.
2. Collaborate with ISA On-Farm Network to compare the effect of commercial seed treatments on seedling diseases, soybean cyst nematode numbers, and soybean yields in on-farm trials.
3. Evaluate fungicide sensitivity of pathogens recovered from diseased soybean seedlings collected from the small plot and on-farm trials.
4. Determine baseline fungicide sensitivity of pathogens recovered from diseased soybean seedings collected from the small plots and the on-farm trials.
5. Determine baseline fungicide sensitivities of economically important Pythium, Fusarium and Rhizoctonia species to new commercial fungicides ethaboxam, sedaxane, penflufen and fluxapyroxade.
6. Educate agribusiness and soybean farmers on seedling diseases and insect pests and their management to increase productivity and profitability while improving environmental stewardship.

• Evaluated 13 commercial seed treatments in small plot trials at each of 3 locations in Iowa.
• Collected the following data: emergence, stand count, seedling disease incidence, sudden death syndrome (SDS) index, SCN egg counts, and insect counts.
• Conducted 37 field trials in collaboration with the ISA On-Farm Network: 7 evaluating ethaboxam for seedling disease management; 13 evaluating Clariva for SCN management; 17 evaluating ILeVO for SDS management. Yield data were also collected for all trials
• Recovered isolates of Pythium and Fusarium from small plot trials to be evaluated for fungicide sensitivity.
• 4 extension publications, 5 national webinars, 6 media interviews and 18 presentations were given to over 3700 stakeholders from Iowa and beyond.

Update:
Data from 2014 small plot trials were analyzed and summarized. An article sharing the combined results from the three locations was posted to Integrated Crop Management News. Briefly, no effect of seed treatment on stand or yield was detected (<0.1). Soil temperatures at planting were relatively warm and it is likely that this reduced the risk of seedling disease.

In 2015, 12 seed treatments will be evaluated in small plot trials at 3 locations in Iowa: Nashua, Kanawha and Crawfordsville. The trials were planted April 16 and 17 and soil temperatures at planting were 53, 56 and 52 at the three locations respectively, respectively. Cool wet weather occurred across Iowa on April 18 and 19. We anticipate that these trials will be an excellent test of seed treatment efficacy.

Data from the 2014 on-farm trials done in collaboration with the ISA On–Farm Network to evaluate ClarivaTM and Intego SuiteTM was analyzed and summarized. An article sharing the results of the Clariva trials was posted to Integrated Crop Management News.The overall mean yield difference associated with Clariva Complete Beans compared to CruiserMaxx Advanced plus Vibrance with was +0.8 bu/acre.

Educational presentations regarding soybean seedling disease and soybean cyst nematode that included data from these trials was shared with Iowa soybean farmers and certified crop advisors at a number of winter meetings

All data from small plot and on-farm strip trials for this period are currently being analyzed.

The sensitivity of Fusarium populations from soybean to the commonly used seed treatment fungicides fludioxonil, ipconazole, pyraclostrobin, and trifloxystrobin was evaluated. Fungicide formulations were incorporated into potato dextrose agar at a range of concentrations (0.01 to 100 µg/ml). Radial growth and spore germination were visually assessed and measured for representative isolates of F. graminearum, F. oxysporum, F. solani, and F. acuminatum from Iowa and surrounding states. These data were compared to results obtained using image analysis software. Mycelial growth inhibition differed significantly among the fungicides and among Fusarium species and strains. Fludioxonil had a stronger effect than ipconazole on radial growth of F. graminearum; in contrast, ipconazole strongly inhibited mycelial growth of F. oxysporum, F. acuminatum and F. solani. Spore germination was strongly affected by both trifloxystrobin and pyraclostrobin. EC50 frequency distributions were generated for each combination of species and fungicide; this information will be valuable for tracking potential future changes in sensitivity.

Data from this project will enable the strategic use of seed treatments for improved soybean stands increased farmer profitability. Moreover, these data will contribute to our understanding of stand loss due to soybean seedling disease and contribute to other projects by these PIs that are currently being funded by Iowa Soybean association, North Central Soybean Research Program and United Soybean Board.

• Emergence, stand count, seedling disease and insect data, SCN counts, SDS index and yield for 13 commercial seed treatments at Crawfordsville, Nashua and Kanawha.
• Yield data for Intego, Clariva and ILeVO seed treatments.
• SCN count data for Clariva and ILeVO seed treatments
• SDS Index data for ILeVO seed treatments
• Data shared with more than 3700 soybean farmers in Iowa and the U.S.
• Fungicide sensitivity (EC50) data to fungicides used in commercial seed treatments
• Presentations and publications to Iowa and U.S. soybean farmers