By Daren S Mueller and Nabin Dangal et.al
In 2025, commercial foliar fungicides were evaluated across six Iowa State University research and demonstration farms to determine their effect on disease control and yield response on soybeans. The locations included the Northwest Research and Demonstration Farm (Sutherland), Northern Research and Demonstration Farm (Kanawha), Northeast Research and Demonstration Farm (Nashua), Wyffles Farm (Central Iowa Research and Demonstration Farms, Ames), Armstrong Memorial Research and Demonstration Farm (Lewis), and Southeast Research and Demonstration Farm (Crawfordsville).
A total of 16 fungicides containing single or multiple active ingredients were evaluated at each location, along with a non-treated control (NTC). Fungicide treatments were laid out in a randomized complete block design with four replications. Plot size ranged from 24 to 35 feet long and 10 to 15 feet wide (4 or 6 rows at 30-inch inter-row spacing). At all locations, the cultivar was XO 2865E (Xitavo Soybean Seed), which was planted at 140,000 seeds/acre in a field that was corn the previous year. Planting dates across the locations and other field activity details are provided in Table 1.
All fungicides were applied using a self-propelled research sprayer at recommended rates at the beginning of pod (R3 growth stage) with nonionic surfactant (Induce at 0.3% v/v) and at a volume of 20 gallons per acre (Table 2). Foliar diseases were assessed between the R5 (beginning seed) and R6 growth stage (full seed). Septoria brown spot (caused by Septoria glycines) was assessed by measuring the height of the highest infected leaf in the canopy, and the disease severity was estimated as the percent of leaf area covered by the disease on the highest infected leaves which was converted to Septoria brown spot severity index (BSX).
Source : iastate.edu