Weather Forecast


TRNP to use aerial spraying to control invasive weeds in North Unit

Aerial spraying of herbicide to control Canada thistle and leafy spurge in backcountry areas is expected to begin in Theodore Roosevelt National Park North Unit on Wednesday. Spraying will continue for two to three days, weather permitting, or until approximately 700 acres have been treated.

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Spraying operations will take place only in the North Unit.

Canada thistle and Leafy spurge are non-native, highly invasive, state-listed noxious weeds which, left untreated, would rapidly increase and interfere with the natural ecology of the park. They could also spread to non-infested land adjacent to the park.

No portion of the park will be closed during the spraying operations. However, visitors should avoid areas which are actively being sprayed.

The herbicides used do not harm native vegetation or wildlife, according to the National Park Service.

“Some visitors may find the low-flying helicopter to be an intrusion,” Superintendent Valerie Naylor said in a statement. “We never want to intrude upon the visitors’ enjoyment of the park, even for a day. However, the need to control leafy spurge and Canada thistle and reduce their impact on the park’s native vegetation makes this short-term inconvenience a necessity.”

Visitors who have questions about the aerial spraying should contact the park at 701-623-4466.