Effect of Priaxor, tank mixes, and other commercial fungicides on frogeye leaf spot of soybean, 2016

摘要

Soybean seed were planted (7 seed/row ft) on 24 May in a Coushatta silt loam soil at the Dean Lee Research Station near Alexandria, LA. Standard chemical and cultural practices for soybean production were followed according to recommendations of the Louisiana State University Agricultural Center. Treatments were replicated three times in a randomized complete block, and separated by 7 ft alleys. Plot size was 4 rows on 38 in. spacing by 20 ft. Fungicide treatments were applied on 26 Jul at soybean growth stage R3 using a CO2-charged spray boom configured with ULD 120-02 flat fan nozzles spaced on 20-in. centers delivering 16.0 gal/A at 30 psi. Rainfall totals for May, Jun, Jul, Aug, and Sep were 2.7, 5.8, 4.5, 13.7, 4.2, and 0.2, respectively. Frogeye leaf spot (FLS) severity was determined on 3 Aug, 12 Aug, and 25 Aug by arbitrarily selecting 10 leaflets per plot and estimating the percentage of leaf area affected using a scale developed with Assess 2.0 (American Phytopathological Society, St. Paul, MN). Area under the disease progress curve (AUDPC) was calculated from the three rating dates. Plots were harvested using a small-plot combine on 5 Oct, and yields were adjusted to 13% moisture. Data were subjected to analysis of variance, and treatment means were compared using Tukey's honest significant difference test (P=0.10).