Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/23/2015
Publication Date: 7/2/2017
Citation: Zhou, X., Dou, F., McClung, A.M. 2017. Organic rice diseases and their management. Proc. 36th Rice Technical Working Group Meeting, Galveston, TX, p. 41-42. March 1-4, 2016. CDROM.
Technical Abstract: Management of diseases is a challenge to organic rice producers. No synthetic chemicals, including fungicides and fertilizers, are allowed for use on organic rice. Instead, organic rice production relies on cultivars, animal and green manures, tillage, water, and other biological measures to maintain soil and plant health and to supply plant nutrients. However, these practices may result in changes in the severity of diseases and their management as compared to conventional practices. This presentation summarizes the results of field studies to manage rice diseases conducted on organically managed land at Beaumont, Texas during 2009 through 2014 using cultivar resistance, cover crop, fertility, tillage and biocontrol management tools. . Organic rice diseases: Disease comparisons were made on more than 20 rice cultivars and elite lines grown under organic and conventional management in 2009-2011. Organically produced rice was more vulnerable to seed rot and seedling diseases, narrow brown leaf spot (NBLS), brown spot, and straighthead than conventional rice. Because of the limited options for disease control, other disease that might cause significant damage to organic rice included sheath blight, sheath rot, blast, bacterial panicle blight, false smut, black kernel, and pecky rice caused by various fungi and bacteria and insect injury. Cultivar resistance: 20 cultivars and elite lines were evaluated for resistance to NBLS and brown spot during 2010-2014. Most cultivars showed a degree of resistance to NBLS. GP2, Jasmine 85, Rondo, Tesanai 2, XL 723 and XL 753 were among the most resistant to NBLS. Cocodrie, Colorado, Cybonnet, Jazzman, Presidio and Sierra were susceptible or highly susceptible to NBLS. None of the cultivars were immune to brown spot and Charleston Gold, Cybonnet, Jazzman, and Jupiter were the most susceptible. Brown spot was lowest on GP2, Tesanai 2 and Wells. Tesanai 2, GP2, and Rondo, all originating from China, had yields that ranked among the highest. Cover crop and fertility: A trial was conducted in 2012, 2013 and 2014 to evaluate the impact of cover crop and organic fertilizer alone or in combination on NBLS and brown spot. Production following the incorporation of clover winter cover crop resulted in a consistent reduction in NBLS and brown spot than following winter fallow. Production following ryegrass cover crop incorporation reduced NBLS in 1 of 3 years and brown spot in 2 of 3 years. Regardless of cover crop, an application of the soil amendment NatureSafe or Rhizogen at 90, 150 or 210 kg N/ha significantly reduced NBLS and brown spot compared to the nonamended control. Tillage practice: Two separate trials were established in 2010 and 2011 to evaluate the impact of tillage on straighthead. White clover was planted in the fall and terminated the following spring. In preparation for planting, one trial was conventionally tilled while the other used no-till prior to direct seeding of the rice crop. 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 the conventional tillage. Biocontrol: Efficacy of seven biocontrol agents for suppression of sheath blight and NBLS was evaluated in sheath blight-inoculated plots in 2010 and 2011. Serenade Max (Bacillus subtilis strain QST713, 14.6% a.i.) and Serenade ASO (B. subtilis strain QST713, 1.34% a.i.) were effective in reducing sheath blight in 2011. Serenade Max also significantly reduced NBLS in both years. Serenade Max increased yield up to 20% over the untreated control. In conclusion, organic rice is more vulnerable to the diseases suc