Evaluation of Stratego YLD applied at different growth states for control of southern rust of corn in Arkansas, 2016

摘要

The premix fungicide, Stratego YLD was applied at two stage of corn growth for protecting corn against southern rust. The trial was conducted in a commercial production field near Pine Bluff, AR. The corn hybrid 'AgVenture R9583' was planted on 20 Mayat a seeding rate of 32,000 seed/A in a Coushatta silt loam previously cropped in soybean. Weeds were controlled per recommendations by University of Arkansas, Cooperative Extension Service. Plots consisted of four, 30 ft long rows spaced 30-in. apart.The experimental design was a randomized complete block design with four replications separated by a 5 ft fallow alley. Fungicides were broadcast through flat-fan nozzles (Tee-Jet 110015VS) spaced 30-in. apart on the two center row per plot using an airpressurized multi-boom plot sprayer. The sprayer was calibrated to deliver 15 gal/A at 32 psi. Treatments were applied at V5 (6 Jun) and VT (12 Jul) growth stage. Severity of southern rust was rated at 13 (25 Jul) and 28 (10 Aug) days after treatment (DAT) based on percent of ear leaf infected near the center of each plot. The center two rows of each plot were harvested on 6 Oct using a K Gleaner combine equipped with a Harvest Master weigh system and moisture was adjusted to 15.5%. Data were analyzed by the GLM procedure and mean separation by Tukey's Honest Significant Difference test at P = 0.05 using Agricultural Research Manager Software (version 9.0). Rainfall during the cropping period totaled 16.01 in. with monthly totals as follows: May, 7.75in.; Jun, 3.43 in.; Jul, 2.60 in.; Aug, 1.65 in.; Sep, 0.58 in. Monthly average maximum air temperatures were 81°F May, 89°F Jun, 93°F Jul, 91°F Aug, 88°F Sep. Monthly average minimum air temperatures were 62°F May, 70°F Jun, 75°F Jul, 71°F Aug,66°F Sep.