Fungicidal efficacy for control of northern corn leaf blight on sweet corn, spring 2015

摘要

Sweet corn of the northern corn leaf blight (NCLB) susceptible bi-color variety 'A&C 7112R' was planted at the University of Florida's Everglades Research and Education Center in Belle Glade on 9 Feb. The soil, classified as Pahokee Muck with a soil pH of 8.2, was fertilized according to soil test recommendations. The field was laser-leveled and fertilizer was disk-incorporated prior to planting. Corn was planted in a 0.8 acre plot with a row spacing of 30 in. and an in-row spacing of 8 in. Plots consisted of two 25-ft rows bordered on the sides by three non-sprayed guard rows. Plots were separated on the ends by 5-ft alleys. Treatments were replicated four times and arranged in a randomized complete block design. Fungicide sprays were applied usinga CO2 backpack sprayer operated at 30 psi and delivering a spray volume of 50 gal/A. A nonionic surfactant, Induce, was added to all fungicide treatments at 0.125% vol/vol. The spray boom was equipped with three Tee-Jet 11003 flat-fan nozzles, with thecenter nozzle located directly above the row. Side nozzles were positioned on 18 in. spray boom drops and were directed inward to maximize coverage on the target row. Treatment rows were sprayed one at a time. Sprays were initiated on 27 Mar at the mature whorl stage. Two subsequent fungicide applications were made on 3 and 10 Apr. Disease was visually assessed by estimating the percentage of foliage necrosis by NCLB at two randomly selected locations per plot on 8 and 17 Apr. Yield was estimated by harvesting 25 randomly selected plants per plot. Total weights of ear samples were recorded, and ears were graded for marketability to calculate the percentage of marketable ears. An estimate of the number of crates per acre was calculated using the % marketable, an ideal plant population of 26,400 plants/A, and 48 ears per crate.