Pacific Northwest Weed Management Handbook

Himalayan knotweed (Polygonum polystachyum) produces lush foliage and sprays of attractive white flowers in summer, but this common ornamental species rapidly spreads to take over gardens and is now widespread on roadsides, noncropland, and forestlands in western Washington and Oregon.
Photo by Tim Miller, Washington State University. Reproduced with permission.

This handbook is designed as a quick and ready reference of 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 of the Agricultural Experiment Stations and Extension Services of Oregon, Idaho, and Washington. A few suggestions are included from research conducted in other states or 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 The handbook is updated quarterly. Individual sections are revised once a year; revision dates are listed at the start of each section. Most sections are also available as PDF documents on this website.

Some sections may include additional online content, such as photos and links to related websites, publications, and other resources. Check the left sidebar of each page for these additions.

Important Points to Remember

• This handbook is not intended as a complete guide to weed control or herbicide use.

• 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.

• Information is supplied here with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied. Trade names (brand names) of some commercial pesticides are used in portions of this handbook to help identify the common name used by the Weed Science Society of America (WSSA). 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 not legal or recommended.

Editor

Ed Peachey, Oregon State University

Associate Editors

Dan Ball and Andy Hulting, Oregon State University
Tim Miller, Washington State University
Don Morishita and Pam Hutchinson, University of Idaho