Effect of Fungicide Seed Treatments on Stand Establishment, Seedling Disease, and Yield of Soybean in North Dakota.

Seedling diseases of soybean (Glycine max) can be common under cool and moist soil conditions and may be caused by a complex of pathogens in North Dakota. Managing these diseases can be difficult due to wide host ranges of the pathogens and lack of resistant cultivars. Field trials were conducted to evaluate the effects of three different fungicide seed treatments and an untreated control on soybean at six locations in 2003 and eight locations in 2004 in North Dakota, for a total of 14 environments. The fungicides evaluated were fludioxonil + mefenoxam (Warden RTA), azoxystrobin + metalaxyl (SoyGard), and Bacillus pumilus GB34 (Yield Shield). Significant (P ≤ 0.05) environment-seed treatment interactions were observed, indicating that environment played a role in when benefits from seed treatments were observed. At least one of the fungicide seed treatments provided significant protection against plant stand and yield losses compared with the untreated control in 4 of the 12 environments where plant stand was measured and 4 of the 14 environments where yield was measured. Root lesions were reduced significantly by at least one of the fungicide seed treatments compared with the untreated control in 5 of the 11 environments where root lesions were evaluated. Yield and economic benefits with fungicide seed treatments were observed more often in environments that had low soil temperatures at planting (<15°C) and moist soil conditions. Based on this research, fungicide seed treatments may be a viable option for soybean growers in North Dakota when planting into cool and moist soil conditions.