Evaluation of fungicide application timing on northern corn leaf blight and yield in field corn, 2014

摘要

A foliar fungicide application trial was done at the Iowa State University (ISU) Marsdon Farm, Boone, IA. The corn hybrid Dekalb DKC57-92, with a resistance rating of 5 for northern corn leaf blight (NCLB;1-10 scale, 1 = best), was planted into a Clarion Webster Nicollet following soybeans in a minimum tillage system on 5 May 2014. The experimental design was a randomized complete block design and each plot was 4 rows wide (30-in. row spacing) by 55 ft long. All plots were bordered by 4 rows on either side, and 5 ft alleys were cut between replications at V4. Fungicides were applied with a CO2 backpack sprayer at either V6 (19 June), R1 (24 July), or at both growth stages using a high clearance plot sprayer fitted with Turbo TeeJet spray nozzle TT11001 spaced 20-in. apart and delivering 15 gal/A at 35 psi. On 18 Sept (1/4 milk line), disease severity in the upper canopy (ear leaf and above) of each plot was assessed. Disease severity was an estimate of percent leaf area diseased at the plot level.All 4 rows of each plot were harvested with a small plot combine on 22 Oct and yields adjusted to 15.5% moisture. All data were subjected to analysis of variance and means were compared at the 0.1 significance level using Fisher's protected least significant difference (LSD) test.