Evaluation of 'curative' fungicide treatments for control of Sclerotinia stem rot of soybean in Wisconsin, 2014

摘要

The trial was established at the Hancock Agricultural Research Station located in Hancock, WI. The soybean cultivar 'AG2031' was chosen for this study. Soybeans were planted in mid-May 2014 in a field with a Sparta loamy sand soil (0 to 2 percent slopes). The field was overhead irrigated as needed to prevent wilt. The experimental design was a randomized complete block with four replicates. Plots consisted of four 30-in. spaced rows, 20 ft long and 10 ft wide with no alleys between plots. Standard soybean production practices as described by the University of Wisconsin Cooperative Extension Service were followed. Treatments consisted of a non-treated control and two fungicide treatments. Fungicides were applied using a CO2-pressurized backpack sprayer equipped with 8001 TurboJet flat fan nozzles, spaced 15 in. apart, and calibrated to deliver 20 GPA. Sclerotinia stem rot severity was rated at growth stage R5 on 21 Aug and fungicides were applied on the same day. Sclerotinia stem rot severity was again evaluated at growth stage R6 (4 Sep). Sclerotinia stem rot severity index (DSI) was determined by rating 30 arbitrarily selected plants in each plot and scoring plants on a 0-3 scale: 0 = no infection; 1 = infection on branches; 2 = infection on mainstem with little effect on pod fill; 3 = infection on main stem resulting in death or poor pod fill. The scores of the 30 plants were totaled and divided by 0.9. Natural sources of pathogen inoculum were relied upon for disease. Yield was determined byharvesting the center two rows of each plot using a small-plot combine. All disease and yield data were analyzed using a mixed model analysis of variance (P=0.05).