Weed Control and Herbicides

If you decide to use an herbicide to control weeds, be sure to select the appropriate product for your situation. There are hundreds of different herbicides on the market.

Control tips:

• Be sure to read, understand and follow all of the label directions when mixing and applying herbicides.
• Make sure the label clearly states that the product can be used in the manner you intend to use it.
• Remember, more is not better. Use the application rate on the label.
• Some herbicides are selective, and only kill certain types of plants, while others are non-selective and kill almost any type of plant.
• Some herbicides kill weeds quickly, others can take up to a week or more.
• Some herbicides persist in plants and soils for long periods of time, while others only remain in plants or soil for a short time.
• Some herbicides have active ingredients that are more likely to move through soils towards groundwater. Others are much less likely to move through soils.

The following list of resources is intended to provide an overview of weed control and herbicides. If you have specific questions about herbicides, or about any of the information provided below, feel free to call NPIC.

If you just want some advice about how to control weeds, you may want to talk with staff at your local cooperative extension service. NPIC Specialists cannot give treatment recommendations, but extension agents often can. NPIC Specialists can answer your questions about an herbicide's potential health impacts, environmental effects, and/or chemical properties. Our mission is to provide objective, science-based information about herbicides in order to empower people to make their own informed decisions.

If you have questions about this, or any pesticide-related topic, please call NPIC at 800-858-7378 (8:00am - 12:00pm PST), or email us at npic@ace.orst.edu.

Weeds

• Identify the type of weed(s) before choosing a treatment strategy.
• Identify weeds you can tolerate. Remove other weeds first.
• Hand pulling weeds before they flower will prevent the spread of weed seeds.
• If you're too late, carefully cut all flower heads and seed-pods off weeds before pulling. You can place them directly into a bag for disposal.
• Deeply water an area and cover with a thick layer of cardboard or plastic to kill all plants present.
• A healthy lawn will naturally fight weeds. Consider mowing on a higher setting, and aerating and fertilizing when needed.
• Water more deeply, and less often, to discourage weeds.
• Mulches (organic, synthetic, or living) can be used to prevent weeds from growing.
• If you choose to use a pesticide, read the label before you buy. Try a lower toxicity product first.
• A few days before spraying, consider cutting the weeds back. Spraying on new growth may lower the amount needed.

If you have a pesticide product in mind, have your label handy and click here for information about that product.

County Extension Offices

Through its county agents, the Cooperative Extension Service gives individuals access to the resources at land-grant universities across the nation. These universities are centers for research in many subjects, including entomology (the study of insects) and agriculture. Each county within the United States has an Extension office, which is staffed with agents who work closely with university-based Extension specialists to deliver answers to your questions about gardening, agriculture, and pest control. You can find the phone number for your local county extension office in the local government section (often marked with blue pages) of your telephone directory or by clicking on the map below.

U.S. States:

AK | AL | AR | AZ | CA | CO | CT | DE | FL | GA | HI | IA | ID | IL | IN | KS | KY | LA | MA | MD | ME | MI | MN | MO | MS | MT | NC | ND | NE | NH | NJ | NM | NV | NY | OH | OK | OR | PA | RI | SC | SD | TN | TX | UT | VA | VT | WA | WI | WV | WY | Washington D.C. |

U.S. Territories:

Puerto Rico | American Samoa | Guam | Northern Mariana Islands | Virgin Islands

Additional Resources:

• Weed Identification - University of California Statewide IPM Program
• Weed Identification - University of Minnesota Extension Service
• Encycloweedia - California Department of Food and Agriculture
• Weed Photos - Weed Science Society of America
• Invasive and Noxious Weeds - US Department of Agriculture
• Plant Fact Sheets and Guides - US Department of Agriculture
• Weed Information - University of California, Davis
• Creating a Weed Management Plan for Your Organic Farm - Penn State Extension
• Weed Management on Organic Farms - NC State University Cooperative Extension
• Paraquat Dichloride: One Sip Can Kill - US Environmental Protection Agency

Lawn/Landscape Weed Control:

• Guide to Healthy Lawns - University of California Statewide IPM Program
• Weed Management in Lawns - University of California Statewide IPM Program
• Weed Management in Landscapes - University of California Statewide IPM Program
• Control of Annual Grassy Weeds in Lawns - Colorado State University Extension
• Guidelines for Herbicide Use - Weed Control Handbook - Global Invasive species Team
• Keep Pets Safe Around Pesticides (p.5-Weeds) - Oregon State University Extension
• Greenscaping: The Easier Way to a Greener, Healthier Yard - EPA
• Moss and Algae Control In Lawns - Clemson University Cooperative Extension Service
• Managing Moss in Lawns in Western Oregon - Oregon State University Extension
• Weed Information - University of California, Davis
• Lawn and Garden Resources - Environmental Protection Agency (EPA)

Selecting Herbicides:

• Herbicides - University of California Statewide IPM Program
• Weed Control Methods Handbook - Global Invasive Species Team
• Weed Management - Illinois Agronomy Handbook, Illinois Extension
• Weed Research and Information Center - University of California, Riverside Extension
• Choosing the Right Herbicide - University of Tennessee Extension
• Herbicide Mode-Of-Action Summary - Purdue University Extension
• Aquatic Plant Management - Washington State Department of Ecology
• Aquatic Herbicides: Essential Information for New Applicators - Oklahoma Cooperative Extension

Alternative Methods:

• Alternatives to Herbicides for Weed Management - CDPR School IPM Program
• Tips for a Healthy Lawn - CDPR School IPM Program
• Non-Toxic Weed Control - Bio-Integral Resource Center
• Hand Weeding - University of California Statewide IPM Program
• Weed Free Lawns - VA Soil and Water Conservation District
• Weed Control Handbook - Global Invasive Species Team
• Maintaining a Healthy Lawn the IPM Way - MA Department of Agricultural Resources