Effects of fungicides on Gray leaf spot and yield of field corn in Ohio, 2007.

摘要

Trials were conducted at the Ohio Agricultural Research and Development Center (OARDC), near Wooster, and at the OARDC Northwest Branch (NWB), near Hoytville. Seeds of Pioneer Brand hybrid 36M28, susceptible to gray leaf spot, were planted on 24 Apr in Ravenna silt loam at OARDC and on 9 May in Hoytville silt clay loam at NWB. At OARDC, each plot consisted of four 25-ft-long rows spaced 30 in. apart, whereas at NWB, each plot consisted of four 80-ft-long rows spaced 30 in. apart. The experimental design was a randomized complete block design, with four replicate blocks. Standard herbicides (2-4 D and Roundup at OARDC and Outlook, AAtrex 4L, and Credit Extra at NWB) were used at label rates, and fertilizer was applied based on a soil test (400 lb/A 19-19-19 and 200 lb/A Urea at OARDC and 28% UAN, (urea ammonium nitrate solution) at 17gal/A at NWB). Fungicide treatments were applied with a high-clearance sprayer fitted with nozzles adjusted to deliver approximately 20 gal/A at 40 psi. Drop nozzles were used at NWB. A single application was made at VT growth stage (tassel emergence), 13 Jul at OARDC and 23 Jul at NWB. Plots were inspected for disease (gray leaf spot) development during the months of Aug and Sep (between late dough and early dent plant growth stages). Six plants were arbitrarily selected from the two center rows of each plot and the percentage of leaf area covered (severity) with lesions of gray leaf spot (GLS) was estimated on the ear leaf and the first (ear -1) and second (ear - 2)leaves below the ear leaf. The two center rows of each plot were harvested on 1 Nov at OARDC with moisture levels ranging from 15 to 18%, and on 19 Oct at NWB with moisture levels between 17 and 19%. Yield is reported as bu/A adjusted to 15.5% moisture.At OARDC, total rainfall for the months of Jul, Aug and Sep was 5.81, 4.76, and 2.17 in, respectively. Total rainfall for the period between 9 Jul and 23 Jul (one week before to one week after silk emergence) was 1.85 in. Minimum, average, and maximum temperatures for Jul, Aug and Sep. were 44, 69, and 91; 50, 73, and 92; and 35, 65 and 92 F, respectively. At NWB, total rainfall for the months of Jul, Aug and Sep was 2.40, 9.29, and 2.12 in, respectively. Total rainfall for the period between 19 Jul and 2 Aug (one week before to one week after silk emergence) was 1.66 in. Minimum, average, and maximum temperatures for Jul, Aug and Sep were 45, 71, and 96; 46, 73, and 94; and 37, 67 and 91 F, respectively.