Washington Friends of Farms & Forests

We Help Washington Grow

What is an herbicide?

An herbicide is a type of pesticide designed to control unwanted plants. Herbicides are designed to affect plants, not animals or humans. Most herbicides are practically non-toxic to humans, fish and animals. 

Many herbicides are less toxic than common household products such as salt, vinegar, coffee, medications and cleaning products. See the chart.

There are no documented cases of injury or illness from herbicide exposure when the product was used according to the label.

Why do weeds need to be controlled?  

Weeds are non-native plants that have been introduced by humans. Many spread rapidly, crowding out native plants and threatening habitat. Some are poisonous to livestock, pets and people.  Others compete with crops or trees and limit production.  Along roads, rail lines and utility corridors, they often create a fire hazard.



Weeds and other vegetation along roadsides needs to be controlled for safety. Vegetation can obscure signs and intersections.  It prevents water from draining increasing the risk of hydroplaning. It can shade the road so frost lingers in winter.  Also, noxious weeds can spread from the roadside into farmers fields.

How do regulations make sure herbicides are safe?

All herbicides are registered and regulated by the EPA (Environmental Protection Agency.) Testing is rigorous and comprehensive.  Directions are written for each product to protect people, fish, animals and the environment.  

Anyone who applies any pesticide (including herbicides) to property other than their own, is required to have training, pass a test, get a license and take continuing education classes.  Professional applicators are also required to keep detailed records.  If an applicator does not follow the rules, he can be fined, lose his license and be barred from applying pesticides in the future.

Many herbicides used commercially are the same as those available at home and garden stores for use by homeowners, though they may be sold under different brand names. 

Yellow-star thistle, an invasive weed species.

Why can't weeds just be pulled?

Pulling may work fine in some situations, but it is not practical along roadsides or in many other locations:


• In order for workers to be safe pulling weeds on roadsides, safety requirements include flaggers and lane closures. Not only is this expensive, it is also inconvenient for drivers. Weeds collected from roadsides must be hauled away and disposed of.


• It is often very difficult to get the entire root out by pulling. If some of the root is left in the ground, most weeds will grow back.


• If the weed is not pulled before going to seed, the infestation spreads. Most weeds set seeds very quickly. With so many miles of roadside to manage, there is simply not enough time to pull all the weeds and prevent them from spreading.


• Herbicides are usually the most cost effective way to manage unwanted vegetation. In many situations, once an herbicide treatment gets the problem under control, additional treatments may not be needed for several years.

Why can't weeds just be mowed or cut?

In some cases, they can.  But mowing does not remove roots and many types of weeds will grow back. In addition:

  • Mowing can spread seeds. Each cut piece can sprout making the infestation worse.
  • Along roads, mowers can throw rocks or other debris onto the roadway causing injury to passing motorists or bicycle riders.
  • Mowing is slow and expensive.
  • The negative environmental effects of mowing with diesel or gas powered equipment is much greater than targeted spraying with herbicides.

Will herbicides kill bees?

Most herbicides are non-toxic to bees.  They are designed to act on plants, not insects.  Some insecticides can harm bees if used improperly, meaning not used according to the product label.


Insecticide labels have specific directions to protect bees.  In general, spraying should be done at times of day when bees are not active.


What if an herbicide gets into the water?

Some herbicides are formulated specifically to control aquatic weeds. Labels are written to protect water quality. When used according to the label, herbicides should not harm aquatic life or recreational activity.

Did You Know?