Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 12/6/2010
Publication Date: 3/28/2011
Citation: Zhou, X., McClung, A.M., Cammack, J.L. 2011. Management of sheath blight and narrow brown leaf spot with biocontrol agents in organic rice, 2010. Plant Disease Management Reports. 5:V120. Interpretive Summary:
Technical Abstract: The experiment was established in a field of League-type soil (3% sand, 32% silt, and 64% clay) under organic management for many years at the Texas A&M University System's Agrilife Research and Extension Center, Beaumont. Plots consisted of seven 18-ft rows, and spaced 7 inches between rows. There were four biocontrol agent treatments: 1) Serenade Max at 3lb/A; 2) Serenade ASO at 6 fl qts/A; 3) Ballad Plus at 4 fl qts/A; and 4) untreated control. These treatments were arranged in a randomized complete block design with three replications. Durana white clove (6 lb/A) and Tam 90 ryegrass (15 lb/A) were planted on 4 Nov, 2009 and mowed on 26 Apr, 2010. Rice (cv Jazzman) was drill seeded at 180 lb/A on 4 May. Plots received 1000 lb/A of organic Nature Safe fertilizer (13-0-0, N-P-K) on 7 May. Plots were irrigated as locally recommended. All plots were inoculated with the sheath blight pathogen by manually broadcasting 100 ml /plot of rice grain and rice hull mixture (1:2 vol/vol) containing R. solani on 9 Jul. On 26 Jul, plots were sprayed with the biocontrol agents at the booting stage, using a CO2 pressurized sprayer equipped with a boom of three TeeJet 8002 nozzles spaced 16 in. between them that delivered 32 gal/A. On 1 Sep, severity of sheath blight, and narrow brown leaf spot was rated on a scale of 0 to 9, where 0 represents no symptoms and 9 represents most severe in symptoms and damage. Narrow brown leaf spot resulted from natural inoculum. Plots were harvested at the maturity stage on 2 Sep using a plot combine, and grain yield adjusted to 12% grain moisture. Sheath blight developed slowly following inoculation, and thus the levels of sheath blight were low at rice maturity. There were no significant differences in severity of sheath blight among treatments. Narrow brown leaf spot, resulting from natural infection, became severe toward the maturity of rice. Serenade Max reduced narrow brown leaf spot severity, while Serenade ASO and Ballad Plus did not. Among the three biocontrol agents evaluated, only Serenade Max significantly increased yield. No phytotoxicity was observed.