Rice Disease Control-88



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Project Leader and Principal UC Investigators

Robert Webster, professor, Dept. of Plant Pathology, UC Davis


With the increasing interest in plowing under rice residue instead of burning it, in fallowing between rice crops and in using green manure, a crucial question must be asked.

A WIDE SWATH-Finding new methods of eliminating rice straw, such as swathing, may have an impact on other parts of the production cycle. Consequently, researchers are examining how rice diseases may be affected by different practices.

What effect do those practices have on the severity of rice diseases? A major effort during 1988 was to set up research sites and to start collecting data:

These systems are being compared:

  1. rice following rice, with straw chopped on the ground or plowed into the soil
  2. fallow following rice with unchopped straw incorporated and irrigated in early summer
  3. rice following fallow where straw was incorporated
  4. rice following rice where straw was burned
  5. straw incorporated, followed by a winter vetch crop
  6. straw burned, followed by a winter vetch crop.

Organisms under scrutiny

In addition, studies were launched to develop biocontrol of rice diseases-in particular, the use of beneficial organisms. To do this, it is necessary to monitor microflora on rice, isolate and identify them, and scientifically determine their potential for disease control and residue degradation.

Experimental activities during 1988 included:

  • Three experimental sites in Butte County, with varying amounts of disease organisms, were selected;
  • Random samples of organisms, taken weekly until harvest and every two weeks afterward, were incubated and identified in the laboratory. This monitoring is continuing.

". . . studies were launched to develop biocontrol of rice diseases-in particular, the use of beneficial organisms."

Preliminary results revealed about 80 different fungi and 60 different bacteria, some of which show evidence of activity against rice disease organisms.

Chemical re-evaluation

Since there are indications that current fungicides may not be available to control seedling disease after this year, field tests of possible replacements were conducted. Apron®, Anchor, Vitavax®, Maneb® and Gus-F-44 were tested at two sites, with Captan® as a standard. The performance of Apron® and Anchor® was comparable to Captan®. All three were significantly better than the untreated controls.

In addition, plant pathologists:

  • Developed a screening technique for resistance to kernel smut.
  • Followed up on research in Louisiana suggesting that the fungicide Ridomil® helps control early dying (crown rot) and seedling disease. However, two trials showed no significant difference between treated and untreated plots.

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