Evaluation of new fungicides for control of sheath blight and narrow brown leaf spot in rice, 2018

摘要

An experiment was established in a field of Crowley fine sandy loam soil (59% sand, 27% silt, 12% clay, 0.7% organic matter, and pH 5.3) at the Texas A&M AgriLife Research Wintermann Rice Research Station, Eagle Lake, TX. The experiment was conductedin a field naturally infested with the narrow brown leaf spot pathogen. Plots consisted of six 16-ft rows, spaced 7.5-in. apart. There were 10 fungicide treatments arranged in a randomized complete block design with four replications. Rice was drill seeded at 90 lb/A on 11 Apr. Plots received 365 lb/A of fertilizer (13-13-13, N-P-K) prior to planting on 5 Apr, and 80 lb N /A of urea (46-0-0) prior to permanent flood on 23 May, and 60 lb N/A of (21-0-0) at panicle differentiation on 14 Jun. For weed control, plots were treated with RiceOne CS (40 oz/A) and Permit (0.67 oz/A) on 18 Apr, Stam M4 (96 oz/A), Bolero 8EC (48 oz/A), Facet 75DF and Permit (0.67 oz/A) on 4 May. For insect pest control, plots were treated with Mustang Maxx on 23 May. All plots were inoculated with Rhizoctonia solani AG1-IA (the sheath blight pathogen) by manually broadcasting 500 cc/plot of rice grain and rice hull mixture (1:3 vol/vol) on 26 Jun. On 5 Jul, plots were sprayed with fungicides using a CO2 pressurized sprayer equipped with a boom of three TeeJet 8002 nozzles spaced 16-in. apart that traveled at 3 mph and delivered 32 gal/A at 40 psi. Sheath blight and narrow brown leaf spot severities were visually rated on 6 Aug using a scale of 0 to 9 where 0 represents no symptoms and 9 represents the most severe symptoms (leaves dead or plants collapsed). Rice was harvested using a plot combine on 8 Aug. Grain yield and moisture were determined, and rice yields were adjusted to 12% moisture content. Milling percentages of heads (unbroken kernels) and total rice (unbroken and broken kernels) were also determined. Before data analysis, sheath blight and narrow brown leaf spot data were transformed first into the percent rank (0 to 100%) using an equation of [100/9*(disease severity - 9) + 100] and then transformed with the arcsine. Data was subjected to ANOVA using SAS version 9.4. Means were separated using Fisher's protected least significant difference test.