The headwaters of the Grande Ronde and Imnaha rivers originate in the high elevation peaks of the Wallowa–Whitman National Forest in northeast Oregon. These rivers flow northward, descending from 9,000 feet as they meander through a diverse mix of federal and private lands before emptying into the Snake River in southeastern Washington.
The two watersheds include some of the most biologically diverse canyon country in the Pacific Northwest, supporting unique plant and animal communities. The steep walled canyons and narrow valleys are prime winter range for elk, bighorn sheep, deer, game birds and non-game wildlife. Native plant communities include federally listed plants of interest such as Spalding’s silene (Silene spaldingii) and MacFarlane’s four o’clock (Mirabilis macfarlanei).
“Invasive weeds are one of the most serious natural resource and economic issues facing the canyon country in Wallowa County,” says Mark Porter, Watershed Stewardship Director for Wallowa Resources and lead for the Wallowa Canyonlands Partnership. Porter began working with the Wallowa Canyonlands Partnership (WCP) in 2000 when a group of committed individuals and agencies realized that without increased coordination, planning, and management noxious weeds would continue to spread in the region.
The Wallowa Canyonlands Partnership encompasses about 1.7 million acres of private and government-owned lands in parts of four counties and three states (Figure 1). Partners in the weed management effort include private, state, Tribal and federal entities that provide technical expertise, local coordination, and funding for noxious weed control (Table 1). “The Bureau of Land Management was one of the driving forces behind the WCP and continues to be a key partner in our effort,” explains Porter.
The mission of the WCP is to protect the ecological and economic values of Hells Canyon along the Imnaha, Lower Grande Ronde and part of the Snake Rivers from weed invasion by coordinating control and restoration projects across jurisdictional boundaries. “Partners work closely toward a shared goal,” Porter explains. “Unfortunately weeds don’t respect land ownership boundaries, and in mixed ownership areas it’s mutually beneficial to cooperate and communicate to avoid duplicate or disparate efforts.” Natural and human-caused factors put the area at high risk for invasion by non-native invasive plants. The WCP focuses primarily on the river corridors because the rivers themselves are significant vectors of weed seed transportation. Floods bring weeds downriver and create a seed bed, thus spreading weeds throughout the watershed.
Ecological change to the area from invasive perennial plants such as St. Johnswort (Klamath weed or goatweed; Hypericum perforatum) began as early as the 1920s in the Clearwater River watershed. Since that time, a host of invasive non-native plants have been introduced, established, and spread. This includes spotted and diffuse knapweed (Centaurea stoebe and C. diffusa), leafy spurge (Euphorbia esulae), hawkweeds (Hieracium spp.), rush skeletonweed (Chondrilla juncea) and others. Today there are 32 “A” designated noxious weeds and 15 “B” designated weeds reported in the project area, with 11 of those prioritized for intensive treatment.*
Successful management of invasive plants hinges on the ability to prevent introduction, and detect and quickly eradicate new infestations before they spread. “It’s impossible to manage invasive plants well if you don’t know the location and magnitude of the infestation you need to manage,” says Porter. Because of the large size of the project area and budget constraints, WCP was interested in a quick, efficient, and reliable method to survey noxious weeds. “We were lucky when we first started the noxious weed project to be able to work with Jason Karl of The Nature Conservancy (TNC) who introduced us to sketch mapping [BOX 1] noxious weeds on large landscapes. It’s worked great for us, when invasive plants are blooming and highly visible we can map up to 60,000 acres of rough canyon country in a day at less than $0.20 per acre. This method doesn’t replace ground-based inventories for newly invading plants such as rush skeletonweed, but the survey data we collect is invaluable as a planning tool,” Porter explains.
Sarah Ketchum, Watershed Stewardship Coordinator for Wallowa Resources manages GPS data for the project. “We have good data for multiple years so we can measure change in weed populations over time to determine whether populations are expanding or receding,” Ketchum explains. As an example, yellow starthistle (Centaurea solstitialis) populations exploded in 2010 and 2011 with increase in moisture during spring and summer. “Since we had good inventory data on yellow starthistle populations we could see that we needed to move quickly with containment and control measures or we would lose 10 years worth of work,” says Ketchum. “It’s important to be ready with solid landowner relationships, maps, partner funding, and an action plan so you can move forward quickly when needed.”
Early Detection and Response
Most weed species actively managed within the WCP area are at low levels of infestations. Keeping these populations in check and finding new infestations before they can spread is critical to the long-term health of the resource. One way the WCP finds newly invading priority weeds in the lower Grande Ronde and Imnaha is through a unique bounty program. The bounty program pays $200 to the first 10 people who find and report new sites of select weeds in the project area. The Rocky Mountain Elk Foundation provided seed money for the program in 2004, and Wallowa Resources has continued the bounty program since. “It sounds like a lot of money, but we do a good job of inventory so it isn’t that easy for people to find a new location of a priority weed,” explains Porter. “It’s a great public education tool and its priceless if we find a new location before the weed has a chance to spread. It can also be a good way for youth organizations to make a little money and learn about the resource at the same time.”
Priority weeds such as rush skeletonweed in the lower Grande Ronde and Imnaha watersheds are targeted for complete containment and control with the goal of eradication. Survey and detection work for rush skeletonweed is done mainly on the ground since the plant is so difficult to map from the air. Porter explains, “We try to treat all infestations of rush skeletonweed each year—in 2011 that was about 100 sites. On non-federal lands, we apply Milestone® at 5 to 7 fluid ounces/acre (fl oz/A) and it’s doing an excellent job of controlling rush skeletonweed. The benefit of Milestone over other herbicides such as Tordon® 22K is that we can treat when the plants are most visible at bloom stage rather than waiting until fall.
The WCP relies on a science-based approach for managing noxious weeds with a goal of restoring functional plant communities. Preventing introduction of newly invading plants, public education and outreach, releasing biological control agents, using herbicides judiciously, and restoring disturbed sites are critical components of the weed management effort.
“We have biological agents successfully established on yellow starthistle, diffuse knapweed, leafy spurge, St. Johnswort and Dalmatian toadflax (Linaria dalmatica),” explains Porter. “Even though infestations of yellow starthistle expanded the previous two years, we believe that the seed-feeding weevil Eustenopus villosus is slowing the spread of the plant especially in native bunchgrass communities.” The toadflax stem weevil Mecinus janthinus has effectively reduced Dalmatian toadflax, and several other biological agents have been effective on diffuse knapweed.
Noxious weed treatment with herbicides in 2010 and 2011 averaged about 1,550 acres per year in the WCP. The largest acreage treated included yellow starthistle, Scotch thistle (Onopordum acathium), and sulfur cinquefoil (Potentilla recta) with the goal to contain populations. Cost-share programs for weed control encourage private land managers to control infestations of priority noxious weeds. The WCP targets 50/50 cost share ratio for approved projects. Depending on the priority of the weed and funding availability, total cost of control may be paid through the program. “We track what herbicides are applied on specific infestations, application rates, environmental conditions, and treatment results in our database,” explains Ketchum. The herbicides selected are based on efficacy on the target plant, land ownership, proximity to water and other environmental conditions. Depending on site conditions and land ownership, either Milesone at 5 fl oz/A or Transline® at 2/3 pints/A is applied on hawkweeds, yellow starthistle, and Scotch thistle.
Although desirable plants respond favorably on many sites once invasive weeds have been removed, restoration is needed in some areas. The goal for restoring a site is to move from annual grass or weed-dominated sites toward a more functional and weed resistant plant community. “We choose seed mixes based on management objectives and site needs,” explains Porter. Depending on the size of the site seeded, either hand tools, rangeland drills or aerial seeding is used along with moderate disturbance to break up litter and prepare a seed bed.
The keys to success in the WCP are strong partnerships and consistent funding for noxious weed control projects. “All of our partners are important to us, but three have consistently provided funds to our project for 12 years including Oregon State Weed Board, Bureau of Land Management and the Rocky Mountain Elk Foundation,” explains Porter. “Our funding partners allow flexibility on where and how the WCP allocates dollars and that has enabled us to put together a system that works. We have the trust, financial support, and good working partnerships with agencies, Tribes, and private landowners. This relationship is priceless and gives us the ability to efficiently manage invasive plants within the WCP. Effective noxious weed control is based on long-term commitment, diligence, and persistence. If you practice those basic tenants you will be successful,” says Porter.
*In Oregon, noxious weeds are classified as either “A”, “B”, or placed on the “Target (or T) List”, with “A” and “T” listed weeds receiving priority for control efforts. The weed list is reviewed and updated annually.
®™Trademark of Dow AgroSciences, DuPont or Pioneer and their affiliated companies or respective owners. Milestone is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. When treating areas in and around roadside or utility rights-of-way that are or will be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas or rotating the treated area to sensitive crops. See the product label for details.
State restrictions on the sale and use of Milestone and Transline apply. Consult the label before purchase or use for full details. Tordon 22K is a federally Restricted Use Pesticide. Always read and follow label directions. ©2019 Corteva.
Published 2012; reviewed and trademark updated June 2019
Diligence and planning are keys to successful cooperative weed management area in Northeast Oregon - Wallowa Canyonlands Partnership uses a science-based approach for managing noxious weeds. By Celestine Duncan. www.techlinenews.com, TechLine Newsletter. May 2012.
FROM 2012 SPRING ISSUE, WESTERN RANGE & WILDLANDS