About the Weed Management Handbook

Yellow starthistle, Centaurea solstitialis

Yellow starthistle, Centaurea solstitialis, is an aggressive winter annual that invades millions of acres in the western United States. It establishes well in rangelands, pastures, cropland borders and recreational areas. Yellow starthistle reduces forage; contaminates crops; reduces accessibility to wildlife, livestock and humans; and can cause “chewing disease” in horses. Currently, six seed-feeding biocontrol agents are used for management. Although seed reduction can be substantial, population-level impacts are often insufficient. In 2019, the root-crown weevil, Ceratapion basicorne, was approved for use in the United States. It can directly kill plants and offers great potential in reducing yellow starthistle across the landscape. USDA APHIS is developing mass-rearing protocols, and initial field releases are expected to begin in 2020-2022.

This handbook is designed as a quick and ready reference for weed control practices and herbicides used in various cropping systems or sites in Idaho, Oregon, and Washington.

This handbook will be useful to Extension agents, company field representatives, commercial spray applicators and consultants, herbicide dealers, teachers, and producers.

Recommendations are based on research results from the Agricultural Experiment Stations and Extension Services of Oregon, Idaho, and Washington. A few suggestions are included from research conducted in other states, and from U.S. Department of Agriculture research centers. In all cases, authors make every effort to list only registered herbicides, and to ensure that the information conforms to product labels and company recommendations.

Revision and Availability This handbook is updated annually. Individual sections are revised once each year; revision dates are listed at the start of each section. Most sections are also available as PDF documents on the weed handbook website:

Some sections may include additional online content, such as photos and links to related websites, publications, and other resources.

Please send comments or suggestions to handbook editor Ed Peachey (ed.peachey@oregonstate.edu).

Important Points to Remember

  • This handbook is not intended as a complete guide to weed control or herbicide use. Authors have assembled the most reliable information available to them at the time of publication. Due to constantly changing laws and regulations, authors can assume no liability for the recommendations.
  • Any use of a pesticide contrary to instructions on the printed label is illegal and is not recommended. Before using any herbicide, read the label on the container. Before a herbicide can be recommended for a specific use, it must be thoroughly tested. The recommendation on the manufacturer’s label, when followed, can prevent many problems arising from the improper use of a chemical.
  • Trade-name products and services are mentioned as illustrations only. This does not mean that the participating Extension Services endorse these products and services or that they intend to discriminate against products and services not mentioned. Commonly recognized trade names (brand names) of some commercial pesticides are used in this handbook to help identify the common name used by the Weed Science Society of America (WSSA), not as recommendations for that particular product.