Title: Biocontrol of sheath blight and narrow brown leaf spot in organic rice Authors
Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: June 1, 2011
Publication Date: June 15, 2011
Citation: Zhou, X., McClung, A.M. 2011. Biocontrol of sheath blight and narrow brown leaf spot in organic rice. Texas Rice Special Section, Highlighting Research in 2011. p. XXIII-XXIV. Technical Abstract: Organic rice production has significantly increased in Texas over the last decade. Texas organic rice acreage exceeded 16,000 acres in 2007, 2008, and 2009. Production is driven by the increased organic rice market and the unique position of Texas that has the ability to rotate large tracts of fallow lands certified for organic production with cattle operations. Due to prohibition from using synthetic pesticides in organic rice, control of pests including diseases is a particular challenge. Sheath blight (ShB) caused by Rhizoctonia solani and narrow brown leaf spot (NBLS) caused by Cercospora janseana are among the major diseases found in organically produced rice. The purpose of this study was to evaluate the efficacy of commercially available biocontrol products for management of these diseases. An experiment was established in a field under organic management for many years at Beaumont, TX. Durana white clover and Tam 90 ryegrass were planted in fall 2009 and mowed in spring 2010. Rice variety Jazzman was drill-seeded. Plots were inoculated with the ShB pathogen at the time of panicle differentiation. Narrow brown leaf spot developed from natural inoculum. Plots were sprayed at the booting stage with Serenade Max (Bacillus subtilis strain QST713, 14.6% active ingredient), Serenade ASO (Bacillus subtilis strain QST713, 1.34% a.i.), Ballad Plus (Bacillus pumilus strain QST2808, 1.38% a.i.), or left untreated as the control. Severity of ShB and NBLS was rated near rice maturity on a scale of 0 to 9, where 0 represents no symptoms and 9 represents most severe in symptoms and damage. Plots were harvested and grain yield adjusted to 12% grain moisture. Sheath blight developed slowly following inoculation, resulting in low levels of the disease at rice maturity. Narrow brown leaf spot became severe toward rice maturity. Serenade Max reduced NBLS severity, while Serenade ASO and Ballad Plus did not. Among the three biofungicides evaluated, only Serenade Max significantly increased grain yield.