Submitted to: Rice Field Day Abstract
Publication Type: Experiment Station
Publication Acceptance Date: July 1, 2012
Publication Date: August 13, 2012
Citation: Zhou, X., Mcclung, A.M. 2012. Rice disease management under organic production. Rice Field Day Abstract. Texas Rice Special Section, Highlighting Research pg. 26-27. Technical Abstract: Interest in organic rice production has increased because of the increased market demand for organic rice. Texas organic rice acreage has constantly increased over the last decade, reaching 32,000 acres in 2012. Texas is now the leading state in organic rice production in the U.S. Organic rice is produced using management practices different from conventional rice cropping systems. Synthetic chemicals, including fungicides, are prohibited for use on organic rice, and thus, management of diseases is a challenge to organic rice producers. In collaboration with the USDA ARS, a series of disease management studies were conducted on organically managed land at Beaumont, Texas in 2009, 2010 and 2011. Disease severity in organic vs. conventional rice: Disease observations and assessments were made on more than 20 rice cultivars and lines grown under organic and conventional production systems over three years. In general, seedling diseases, narrow brown leaf spot (NBLS), and brown spot were more severe in organic than conventional plots. In contrast, bacterial panicle blight and sheath blight were lower in severity in organic plots than in conventional plots. There were no significant differences in severity of leaf smut and false smut observed between these two cropping systems. Cultivar resistance: Most of the 18 cultivars and lines evaluated in the 2-year study showed resistance to NBLS. Cultivars GP2, Jasmine 85, MCR02-1572, Rondo, and Tesanai 2 were highly resistant to NBLS. However, Cocodrie, Colorado, Cybonnet, Jazzman, Presidio, and Sierra were susceptible or highly susceptible to NBLS. No cultivars were immune to brown spot. Charleston Gold, Cybonnet, Jazzman, Jupiter, and MCR02-1572 had highest levels of brown spot. Brown spot was least on GP2, Tesanai 2, and Wells. Tesanai 2, GP2, and Rondo, all originating from China, had yields that ranked among the highest. Biocontrol agents: Efficacy of seven commercial and experimental bacterial biocontrol agents for suppression of sheath blight and NBLS was evaluated in sheath blight-inoculated trials in 2010 and 2011. Serenade Max and Serenade ASO (both using Bacillus subtilis as the active ingredient at different rates) were effective in reducing sheath blight in 2011 but not in 2010. Serenade Max also significantly reduced severity of NBLS in both years. Serenade Max increased yield up to 20% over the untreated control in the 2-year study. The results of this study indicate that use of some biocontrol agents such as Serenade Max can reduce the damage caused by sheath blight and narrow brown leaf spot in organic rice. Tillage practice: Two separate organic field trials were established in 2010 in 2011 to evaluate the impact of tillage on severity of straighthead. White clover was planted in fall and terminated the following spring. In preparation for planting, one trial was conventionally tilled while the other used no-till. In the no-tilled plots, straighthead occurred in all 20 cultivars evaluated, with Cocodrie and its derived lines, Antonio and Colorado, having the most severe symptoms while other cultivars, including Presidio, GP2, Rondo, and Tesanai 2, showed considerable resistance. In contrast, no symptoms of straighthead were observed in any of the cultivars using conventional tillage and water-seeding. The results of this study indicate severe straighthead is most likely to occur in susceptible cultivars under no-tilled organic production systems involved with direct seeding of rice into a cover crop. In conclusion, organically produced rice is more vulnerable to infection by NBLS and brown spot than under conventional management. Selection of a resistant cultivar with high yielding potential is the most effective means to reduce damage caused by these diseases. Use of biocontrol agents such as Serenade Max also is an option for managing NBLS and sheath blight. Serenade Max and Serenade ASO are commercially available biopesticides certified for organic production of rice and other crops. Use of conventional tillage and planting with resistant cultivars is the best means for preventing straighthead.