Submitted to: Rice Field Day Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/11/2013
Publication Date: 7/11/2013
Citation: Zhou, X., Liu, G., Handiseni, M., Anders, M.M., Jia, Y. 2013. Brassica cover cropping for management of sheath blight of rice. Rice Field Day Abstract. Beaumont, Texas Rice Field Day 2013. Special Section: 17. Interpretive Summary:
Technical Abstract: Sheath blight, caused by Rhizoctonia solani, is the most important disease limiting rice production in Texas and other rice-producing states. The fungal pathogen survives between crops as soilborne sclerotia and mycelium in infected plant debris. These sclerotia and colonized plant debris float on the surface of irrigation water, serving as primary inoculum that infects lower sheaths of rice plants at the waterline. We initiated a multistate collaboration research project with a focus on investigating the potential of utilizing brassica cover crops for management of this soilborne disease. Brassica plants (Brassica spp.) contain glucosinolates and are able to produce the toxic gases, isothiocynates, which can kill R. solani and many other pathogens. Through this biofumigation process, brassica crops have the potential of suppressing sheath blight by reducing primary R. solani inoculum in soil. A field experiment was conducted in R. solani-inoculated plots in Texas and Arkansas to evaluate the efficacy of brassica cover crop and plant growth-promoting rhizobacteria (PGPR) alone and in combination with a reduced rate of azoxystrobin for the control of sheath blight in 2011 (Texas only) and 2012. This trial was conducted as a split plot design with four replications. Main plots consisted of two cover crop treatments: 1) brassica ‘Caliente 199’ and 2) fallow. Subplots were five treatments: 1) Bacillus subtilis PGPR strain MBI600, 2) combination of PGPR strain MBI600 with Quadris (azoxystrobin) at 4.5 fl oz/A, 3) Quadris at 4.5 fl oz/A, 4) Quadris at 9 fl oz/A, and 5) unsprayed control. The brassica crop was planted in fall and incorporated into soil the following spring in Texas (Fig. 1) while in Arkansas, the brassica crop was planted early spring and incorporated into soil in late spring. Seed of the susceptible rice cultivar Cocodrie was treated with strain MBI600 prior to seeding. At the boot stage, plots were sprayed with strain MBI600 or azoxystrobin. Sheath blight severity was assessed near maturity. Plots were harvested using a plot combine and grain yield determined. In Texas, sheath blight severity was significantly lower in plots seeded to brassica cover crop than in plots left fallow the winter in either year. However, the brassica cover crop treatment did not improve grain yield compared to the fallow treatment. PGPR alone reduced disease severity but did not increase yield. Combined use of brassica cover crop with PGPR or azoxystrobin at the half rate significantly improved the efficacy on sheath blight control. Combination of all these three further reduced sheath blight and improved yield, achieving similar efficacy as did azoxystrobin at the full rate. Similar results were also observed in the Arkansas field trial. The results of this study indicate that use of the brassica crop in combination with PGPR and fungicide may offer a new alternative to management of sheath blight in rice.