Applying and Managing Pesticides

Applying Herbicides

There are several ways that pesticides may be applied on forestland:
  • Aerial application, typically done by helicopter, and used with a large area (typically, more than 5 acres); 
  • Road-side spraying, often by a specially equipped truck with motorized spray equipment attached; or
  • Hand application, which is applied to smaller areas and directly to individual tree stems or stumps.
All persons in charge of applying chemicals on forestland must have completed training and licensing through Washington State Department of Agriculture
Those aerially applying pesticides on forestland must first obtain permits from Washington State Department of Natural Resources (DNR).
Read more about how DNR and other agencies regulate forest chemical applications.
Find more information about Washington state laws for handling, storage and application of pesticides here.

Understanding Herbicides


An herbicide may contain one or more active ingredients. The active ingredients are the ingredient(s) that kill weeds. Each active ingredient may have a different toxicity. One easy way to estimate the toxicity of a pesticide product is to look at the signal word. Most pesticides will have either the word CAUTION, WARNING, or DANGER on the label, and that signal word reflects the toxicity of the product:
  • CAUTION represents the lower toxicity products
  • WARNING indicates medium toxicity products
  • DANGER stands for the highest toxicity products

More Information about Pesticides

For information on reporting a spill in Washington see the Department of Ecology’s Spill Reporting and Cleanup in Washington State
Department of Ecology Region offices:
Northwest Region
(425) 649-7000

Island, King, Kitsap, San Juan, Skagit, Snohomish and Whatcom counties
Southwest Region
(360) 407-6300

Clallum, Clark, Cowlitz, Grays Harbor, Jefferson, Mason, Lewis, Pacific, Pierce, Skamania, Thurston and Wahkiakum counties
Central Region
(509) 575-2490

Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan and Yakima counties
Eastern Region
(509) 329-3400

Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla and Whitman counties