Evaluation of fungicides for control of foliar and stem diseases of late-planted soybean in Kentucky, 2006

摘要

A soybean fungicide trial was planted 29 Jun at the University of Kentucky Research and Education Center in Princeton, KY. Plots consisted of 6 rows, 20 ft long, with a between-row spacing of 15-in. and a seeding rate of 11.7 seeds/ft. Treatments werearranged in arandomized complete-block design with five replications. A 10 ft alley separated blocks. Fungicide treatments were applied as a foliar spray at one or more of the following dates (growth stages): 1 Aug (V5-6 growth stage), 14 Aug (R3), 5 Sep (R5.5), and11 Sep (R5.8).Fungicide sprays were applied using a CO2-pressurized hand-held sprayer fitted with Hydro nozzles (dual-configuration spraying fore and aft) and TeeJet 8003VS spray tips, delivering 20 gal/A at 50 psi. A foliar disease complex (i.e., brown spot, Cercospora leaf blight, frogeye leaf spot) was rated on 19 and 28 Sep by visually estimating disease severity as a percent of leaf surface area affected in the upper canopy of each plot. On 18 Oct, stem anthracnose was rated by visually estimating the percent ofstem surface area affected. The incidence of yellow leaves and defoliation in plots was estimated as a percent of total leaves per plot on 28 Sep and 5 Oct, respectively. The center four rows ineach six-row plot (16 ft length) were harvested on 24 Oct using a Wintersteiger Delta plot combine. Yields were adjusted to standardmoisture content and were based on a 60 lb/bu test weight. Percentage data were transformed (arcsine) and analyzed using ANOVA andStudent-Newman-Keuls test (P <= 0.05). Although statistics provided are based on arcsine-transformed data, arithmetic means are presented in order to provide a better indication of the level of disease control provided by each treatment, as well as the overall disease pressure in the trial.