by Josh Wagoner, EDRR Coordinator, Montana Department of Agriculture, josh.wagoner@mt.gov

Introduction

After prevention, early detection and rapid response (EDRR) is the most time and cost-effective way to manage invasive plants. Montana Department of Agriculture’s (MDA) EDRR Program works with partners across Montana to prevent widespread infestations of new threats, protecting agriculture, natural resources, and native ecosystems. Summer 2025 saw both encouraging and concerning developments in these efforts. This post highlights a few EDRR endeavors, helping to raise awareness and hopefully contributing to continued or greater success in 2026.

Successes

Three people standing near an ATV in a grassland. There are hills with scattered trees in the background.

Finding the last dyer's woad on fall's first frigid day. Photo: Josh Wagoner, MDA.

Dyer’s woad (Isatis tinctoria) has long been the Montana EDRR success story, which continued in 2025, but success is being seen with other species too. Tansy ragwort (Senecio jacobaea), mainly a problem in northwestern Montana forests plus a lone site in Lewis and Clark County, keeps declining in number thanks primarily to Lincoln County’s lead. Things are going so well with tansy ragwort that reclassification from Priority 2A to 1B is being considered. Scotch broom (Cytisus scoparius), limited to isolated populations in Sanders and Lincoln counties, is also being considered for reclassification from 1B to 1A, due in part to Montana Department of Transportation prioritizing right-of-way treatments. Finally, non-native common reed (Phragmites australis ssp. australis) was confirmed in Gallatin County, while three suspected sites in Flathead and Lincoln counties were determined to be native after genetic testing. It’s a success to catch this cryptic invader before it becomes widely established.

Concerns

A person standing alongside a road pointing at a ditch. The ditch is filled with a tall, green grass with reddish brown inflorescences.

New Gallatin County invasive common reed site.  Photo: Josh Wagoner, MDA.

Rush skeletonweed (Chondrilla juncea) continues to slowly spread, and Palmer amaranth (Amaranthus palmerii) popped up in multiple locations this summer in Montana. Both species are very difficult to spot and treat, rush skeletonweed because it has so little plant material above ground and so much below ground, and Palmer amaranth because it looks similar to many other species in the Amaranth family, it grows quickly and produces abundant seed, and it easily develops herbicide resistance. Thankfully new rush skeletonweed sites found in Beaverhead and Broadwater counties were each only one or two plants, and Palmer amaranth plants were all removed before seed production. We are preventing or containing both species much better than many nearby states. 

Learn More

For a more in-depth update on these and additional EDRR species, join the Fall 2025 EDRR Webinar on Tuesday, December 16, at 9:00 a.m.  Visit MDA’s EDRR Program and look for the agenda and meeting link in the “Events" section at the bottom of the page.

Further Information

For more information about this month's weed post, contact Extension Invasive Plant Specialist Jane Mangold. Past posts are available in the Monthly Weed Post Directory.

This weed post is also available as a printable PDF (292 KB).