Evaluation of Aproach Prima fungicide for management of frogeye leaf spot of soybean in Arkansas, 2018

摘要

Foliar fungicides were evaluated as a solo and tank mixes for control of strobilurin-resistant frogeye leaf spot. This trial was located at the Newport Extension Station in Newport, AR in a field of Dundee silt loam previously cropped to soybean. Thesoybean cultivar 'GoSoy 4814' was planted on 8 Jun at a seeding rate of 150,000 seed/A. Weeds were controlled using Liberty (1 qt/A), Roundup Power Maxx (1 qt/A), and Boundary (1 qt/A) applied pre-plant on 6 Jun followed by Roundup (1 qt/A), Prefix (2.3pt/A), and ENC (1 qt/A) applied post emergence on 2 Jul. Plots consisted of four, 27-ft long rows spaced 30-in apart. The experimental design was a randomized complete block design with four replications separated by 3-ft fallow alleys. Plots were inoculated with approximately 4,000 spores/A of several different isolates of strobilurin-insensitive Cercospora sojina on 1 Aug using a mudmaster sprayer and irrigated overhead to promote disease development. Rainfall and Irrigation during the cropping periodtotaled 26.14 in. with monthly totals as follows: Jun, 2.0 in.; July, 3.8 in.; Aug, 8.2 in.; Sept 7.4 in.; Oct, 4.8 in. Monthly average maximum air temperatures were 92oF Jun, 91oF July, 88oF Aug, 84oF Sept, and 72oF Oct. Monthly average minimum air temperatures were 72oF Jun, 72oF July, 69oF Aug, 66oF Sept, and 52oF Oct. Fungicides were broadcast through flat-fan nozzles (Tee-Jet 110015VS) spaced 30 in. apart on the two center rows per plot using an air pressurized multi-boom plot sprayer. The sprayerwas calibrated to deliver 15 gal/A at 32 psi. All treatments were applied at the R3 growth stage on 6 Aug using a NIS surfactant at 0.25 % v/v. Frogeye leaf spot severity was assessed at 0, 14, and 29 days after treatment (DAT) based on percent leaf area affected of the upper 1/3 of the plant canopy. Plots were harvested on 4 Dec using a K Gleaner combine equipped with a HarvestMaster Single BDS HiCap weigh system. Data were subjected to ANOVA using Agricultural Research Manager Software (version 9.0)and means were compared using Tukey's honest significant difference test (P = 0.05).