Research Program Area: Ecosystem & Multimedia Effects
Effects of Various Methods of Rice Straw Disposal on the Epidemiology of Rice Stem Rot. Sclerotium.oryzae, the cause of stem rot overwinters either in rice residue or free in the soil. Previous studies have shown that burning of rice residue is more effective in limiting carry-over and increases in inoculum levels than soil incorporation. A three-year study to compare effects of removal of straw with fall and spring burning and incorporation on inoculum levels was carried out. When rice was harvested at 0-3" straw baled and removed followed by stubble disk plowing in the fall or spring or mold-board plowing in the spring. inoculum levels and stem rot disease severity did not differ significantly from treatments where straw was burned in fall or spring. Treatments where rice was harvested 9-12" followed by soil incorporation or baling and removal. resulted in two- to five-fold increases in inoculum level accompanied by increases in stem rot disease severity and losses in yield. The results indicate that harvest of straw at or near ground level followed by removal of residue as completely as possible is as effective in minimizing stem rot inoculum levels as is fall or spring burning under conditions of continuous rice cropping. The effects of in orporating infested rice straw or free sclerotia on carry-over inoculum levels are described and discussed. This report was submitted in fulfillment of standard Agreement No. 9077 by Robert K. Webster and W. W. Bockus, Department of Plant Pathology, University of California under partial sponsorship of the California Air Resources Board. Work was completed as of February 1, 1978.
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