Weed Control-91



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Project Leader and Principal UC Investigators

D. E. Bayer, Professor of Botany, UCD

J. E. Hill, Extension Agronomist, UCD

T. C. Foin, Professor of Environmental Studies, UCD

J. Webster, Staff Research Associate, Agronomy and Range Science Department, UCD

E. Roncoroni, Staff Research Associate, Botany Department, UCD

S. C. Scardaci, Farm Advisor, UCCE Colusa County

J. Brandon, Laboratory Assistant

J. Breen, Research Assistant

G. Fitzgerald, Research Assistant, Agronomy and

Range Science Department, UCD


Research into rice weeds - the biggest pest problem - focuses on new chemical methods of control; improvements in the performance and safety of herbicides currently in use; development of integrated rice management systems; and studies of the biology and physiology of rice weeds.

A limited number of new herbicides were tested for their ability to control weeds in water-seeded rice. Two new experimental herbicides, KIH 2023 and KIH 6127 from Kumiai Chemical Co., looked extremely promising for watergrass control at rates well below those of the currently used grass control herbicides.

A new herbicide from American Cyanamid, AC 322,140, controlled broadleaf weeds similar to Londax®. Researchers next will examine combinations of this new herbicide with grass control herbicides.

Combinations of Facet® (BAS 514) with Ordram® and Bolero® for watergrass control also looked promising, especially in view of the erratic performance of Facet® alone in previous studies.

Continuing studies with Londax® rate and timing confirmed results from previous years that show the 3/4 to 1 ounce rate controlled broadleaf weeds and sedges under most conditions. This work also showed that applications even at the six-leaf stage of rice, although late, could control weeds if necessary.

Studies with postemergence grass herbicides showed more injury with Poast® than with Whip®.

Researchers also report progress in computer modeling and experimental analysis of weed-rice competition. Its value as a management tool is that it may be able to predict losses due to different kinds of weeds and help determine the most cost-effective control given a certain weed mixture. New, as well as existing studies, will be used to test the effectiveness of the program's ability to predict rice-weed interactions.

Researchers also looked into rice weed biology. Greenhouse, growth chamber and laboratory studies were conducted at UC Davis on the physiology of redstem, perennial arrowhead and herbicide-treated rice. The purpose of the greenhouse and laboratory studies on rice treated with herbicides is to evaluate:

  • Techniques to enhance herbicide activity and minimize injury to rice.
  • The influence of Londax® on root development of rice.

The purpose of research on redstem and perennial arrowhead was to learn how these weeds germinate and establish in rice fields.

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