Weed Control - 88



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Project Leader and Principal UC Investigators

David Bayer, professor, Department of Botany, UC Davis

Jim Hill, Extension agronomist, Dept. of Agronomy and Range Science, UC Davis


ONE OF MANY-There are dozens of different plants that fit the grower's definition of weed. The water hyssop, primarily a problem in the San Joaquin Valley, can spread out into a large, submerged mass, choking the life out of young rice plants early in the season.

Tests of the experimental herbicide Londax®, as in previous years, showed encouraging results on broadleaf weeds.

Londax® gave effective control of roughseed bullrush, smallflower umbrellaplant, redstem and arrowhead at any time between the twoleaf and the well-tillered stage of plant growth. Barnyardgrass was partially controlled by Londax® at higher rates and later timings; ducksalad was not controlled with later applications. For most broadleaf weeds, control was adequate at 1 ounce per acre.

Combinations of Londax® with Ordram®, Bolero® or Basagran® controlled both grass and broadleaf weeds as well as current methods.

Facet again showed some promise for watergrass control at 0.05 to 1 pound/acre, but results were variable. Several new herbicides were evaluated for weed control and crop injury under California conditions.

These herbicide trials provided new evidence that proper timing of herbicide application is crucial. The researchers reported: "The rice must be well established and the weeds must be large enough for proper coverage by the herbicide. But once rapid tillering or flowering is reached, herbicide efficacy diminishes and good weed control is lost."

Other experiments were aimed at better integrated pest management and better understanding of rice weed biology. Among the findings:

  • Various water management practices did not influence roughweed bullrush control by Londax.®
  • Redstem did little damage until it reached about the same hieght as the rice, when it branched and shaded the crop. In addition, the weed's green biomass interfered with harvesting and drying.
  • Seed germination of roughweed bullrush is strongly influenced by seed burial (stratification) and light/temperature interaction.

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