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State delays new rules for herbicide tied to C.O. tree deaths


At the manufacturer’s request, state regulators said Tuesday they have postponed new limits on an herbicide tied to Central Oregon tree deaths in recent years.

The Oregon Department of Agriculture said it received a request last Wednesday from Bayer Crop Science LP, Environmental Science Division, to postpone the date of the proposed permanent rule (OAR 603-057-0392) limiting the use of aminocyclopyrachlor , an herbicide also known as ACP.

The proposed permanent rule, which was drafted by ODA after meeting with stakeholders and the public, was scheduled to be adopted two days later.

Upon receipt of a timely request, the department is required by law (ORS 183.335(4)) to postpone the date of its intended action at least 21 days, and no more than 90 days, from the earliest date that the rule could have become effective. Therefore, ODA is postponing the adoption of the proposed permanent rule until no sooner than April 1.

During this time, the department will also reopen the public comment period to allow all interested persons, including Bayer, the opportunity to submit data, views or arguments regarding the proposed rule. Public comment will close on April 5. Email comments to or mail to Oregon Department of Agriculture c/o Andrea Sonnen , Pesticides Program, 635 Capitol St. NE Suite 100, Salem, Oregon 97301.

ODA first adopted a temporary rule (OAR 603-057-0391) limiting the use of ACP in September 2018 after finding tree deaths next to ACP-treated right-of-way sites in Central Oregon. After 18 of 22 foliage samples from those trees tested positive for ACP three years after the last application, ODA drafted and proposed a more comprehensive permanent rule and gathered feedback from stakeholders and the public.

The temporary rule expires on March 26 Now that ODA must postpone the adoption of its permanent rule, this means that, until a permanent rule is adopted, the agency said pesticide applicators can use ACP on all labeled sites, as long as they follow the instructions on the label.

ODA urges pesticide applicators to use caution when applying any product containing ACP in areas where the roots of non-target trees or shrubs may extend. Remember that tree roots may extend well beyond the tree canopy. Depending on the size of the tree, it may take several years before symptoms of herbicide exposure can be seen.

For more information about ACP and rulemaking, visit

For questions, contact Rose Kachadoorian , 503-986-4651

Dale Mitchell, 503-986-4646

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