| Section Four: Noxious Weed Control |
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| Introduction |
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Our mission is to protect Oregon’s natural resources from the invasion and proliferation of exotic noxious weeds. The Noxious Weed Control Section does this by
- providing leadership and coordinating noxious weed management
- serving as a technical resource for noxious weed issues
- providing public outreach, education, and awareness
- conducting weed risk assessments
- detecting new invaders and implementing rapid response control projects
- coordinating and implementing biological control of weeds
- administering the State Weed Board grant program.
From left to right rear: Ken French, Tom Forney
Middle: Eric Coombs, Dave Langland
Front: Glenn Miller, Jo Davis, Beth Meyers, Bonnie Rasmussen, Bob Barrett, Tim Butler, Dan Sharratt
The following is an overview of the Noxious Weed Control Program and a brief summary of major activities for 2005.
The Noxious Weed Control Program has 11 technical staff located in Salem, Canyonville, Klamath Falls, Redmond, Burns, and Union. The program also employs seasonal staff during the field season to assist in the implementation of noxious weed control projects statewide.
The Noxious Weed Control Program provides statewide leadership for coordination and management of state listed noxious weeds. The state program focuses on early detection and rapid response projects for new invasive noxious weeds, implementing biological control, implementing statewide inventory and survey, assisting the public and cooperators through technology transfer and noxious weed education, maintains noxious weed data, and provides assistance to land managers and cooperators with integrated weed management projects. The Noxious Weed Control Program also supports the Oregon State Weed Board with administration of the OSWB Grant Program, developing statewide management objectives, maintaining the State Noxious Weed List, and developing weed risk assessments.
Noxious weeds do not respect ownership and watershed boundaries; effective management requires support and participation from all affected parties. Cooperative management of noxious weeds allow for prioritizing activities and better uses of limited resources to meet the challenging needs of noxious weed management. Partnerships allow management across jurisdictional and ownership boundaries. For these reasons we seek to increase communication, improve coordination, gain cooperation, and assist planning and implementation of projects among cooperators. The State Noxious Weed Control Program encourages and supports partnerships between private landowners, state agencies, federal agencies, tribal governments, counties, weed management areas, watershed groups, conservation organizations, and other weed control entities in the state.
The Oregon State Weed Board (OSWB) is a seven-member board appointed by the director of the Department of Agriculture. The primary mission of the OSWB is to guide statewide noxious weed control priorities and to award noxious weed control funds. Priorities are developed in part through the state noxious weed control policy and classification system by listing and prioritizing noxious weeds.
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| 2005 Weed program highlights |
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During 2005, the Noxious Weed Control Program implimented 125 projects. A total of 888 noxious weed treatments were made by staff using integrated control. Of this, 798 sites were treated with herbicides and 90 sites were treated either manually or by mechanical methods. There were 555 treatments made on federal lands, and 333 treatments on private, county or state lands.
Biological agents were released at more than 108 sites in Oregon during 2005. Over 143 biocontrol sites were monitored to determine establishment and impact of biocontrol agents.
OSWB Grants: Reviewing noxious weed control grants and submitting recommendations to the Oregon State Weed Board for approval and monitoring of awarded grants were key accomplishments once again in 2005. The OSWB received 83 grant proposals in 2005.
Tansy ragwort
Western Oregon has experienced a resurgence of tansy. Monitoring has shown biocontrol agents are present and widespread.
Spartina
Two occurrences of Spartina alterniflora were found this summer.
Small broomrape, Orobanche minor
Two new sites were found this summer.
Blackberry rust, Phragmidium violaceum
In the spring 2005, an exotic pathogen that attacks Himalayan blackberry was detected in Curry and Coos Counties by ODA staff.
Giant hogweed, Heracleum mantegazzianum
Five new sites were found this field season, most occurring in the north Willamette Valley around Portland.
Kudzu, Pueraria lobata
Kudzu was identified for the first time in Oregon in 2000; follow-up monitoring found regrowth at one site in 2005.
Meadow hawkweed
During 2005, treatment of the Lolo Pass hawkweed site continued. Hawkweed was also a point of interest in Central Oregon. A Bend area nursery was found to be selling orange hawkweed.
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| 2005 Noxious weed list update |
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An important function of the Noxious Weed Control Program is identifying new invasive weed species before they become firmly established in Oregon. Plant risk assessments are tools that assist in the listing of new species by gathering background information. Priority activities include networking with weed professionals worldwide, identifying the highest risk species, and conducting yearly surveys to detect new populations as they occur.
Not all recently recognized invasive species are new to North America. Certain ornamental species that have been planted for years are now raising concerns because of their invasive nature. Species that have come to the forefront include English ivy, pampas grass, and butterfly bush. Discussions between ODA, State Weed Board, and the nursery industry are essential so that solutions acceptable to interested groups can be attained.
Noxious weeds are defined by the Oregon State Weed Board as exotic, non-indigenous plant species that are injurious to public health, agriculture, recreation, wildlife, public or private property. As of February 2005 there are 105 species of state-listed noxious weeds in Oregon.
Four weeds were added to the State Noxious Weed List in February 2005:
- Yellow flag iris, Iris pseudacorus
- Yellow floating heart, Nymphoides peltata
- Policeman’s helmet, Impatients glanulifera
- Garlic mustard, Alliaria petiolata
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| Noxious weed control grants |
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The Oregon State Weed Board (OSWB) will receive approximately $1.3 million of Measure 66 Lottery funds for noxious weed control grants in the 2005-2007 biennium. Priority projects were those that restore, enhance, or protect fish and wildlife habitat and watershed function. There continues to be substantial amounts of time allocated by noxious weed control program staff in the review, administration, and monitoring of the Noxious Weed Grant Program. The first of four grant cycles for the biennium was completed in 2005. Sixteen grants were awarded by the OSWB totaling $179,240.
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| Summary of early detection and treatment activities |
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Annual treatments for the control of “A” (highest priority) and “T” (target) designated weeds have reduced the net acreage of many large weed populations. Annual intensive control efforts for distaff thistle, Carthamus lanatus, and purple/Iberian starthistle, Centaurea calitrapa, C. iberica, have achieved 99 percent control on most sites. Douglas County contains most known distaff thistle sites; one site is known from Josephine County. Purple/Iberian starthistle is found only in Clackamas County and is fully contained. Purple/Iberian starthistle has the potential to invade 1.5 million acres in Oregon, which equates to a potential economic impact of $12 million per year.
Early detection and rapid response (EDRR) is a primary activity of the ODA program. ODA approaches EDRR by working with cooperators and developing partnerships to identify species of concern, distribute information, and implement projects. A primary activity is utilizing a risk assessment process with the Oregon State Weed Board to list species on the State Noxious Weed List as “A,” “B,” or “T.” Priority listed species are incorporated into presentation and outreach activities to cooperators and the general public. Surveys for early detection are conducted; pest alerts and other information are produced and distributed to increase awareness in an effort to find and report infestations. Rapid response projects are implemented to eradicate or contain new invaders. An economic analysis reveals a 33:1 benefit to cost ratio for projects of this type.
ODA continues to meet program goals to limit or reduce acreages of all “A” rated weeds and implement project for “A” and “T” listed species. Statewide management plans for “T” weeds are updated each January to identify priorities for the field staff as new problems arise. Weed awareness and weed site reductions continue to be achieved through public education, implementation of chemical control and containment projects, and biological control projects targeting susceptible weed species. The following are a few highlights of “A” and “T” weed projects for 2005.
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| Paterson's curse |
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Paterson’s curse, Echium plantagineum, is a new invading weed in Oregon. It was first detected in August of 2003 in Linn County. In 2004 a second infestation was confirmed on hillside pasture in Douglas County. Paterson’s curse is originally from Western Europe and the Mediterranean region; it is widespread in temperate zones and extends into the tropics. In Australia it has become a serious weed of grazed pastures, grain production areas and natural areas. Since the 1800’s, it has spread rapidly; it is now estimated to cost Australia $30 million annually in lost production. Paterson’s curse is a prolific seeder and can germinate under a broad range of environmental conditions. Once established, it is quite drought tolerant and competitive with other species.
Delimiting surveys were completed for the project area in central Linn County in 2003 and additional survey was done at the new site location in Douglas County during 2004 to determine the distribution and spread of the population. The Linn County population is limited to four locations on field boarders in the Lebanon area. All of the locations were intentionally planted as part of a wild flower seed mix. The populations were treated to prevent seeding and to control the existing plants. In May 2004, a large infestation consisting of 100 net acres/300 gross acres of Paterson’s curse was identified Southeast of Dillard in Douglas County. Meetings were held with landowners and neighbors. Eighty net acres of the project area was sprayed with a helicopter in 2004, with 20 net acres of additional ground treatment. All 2005 treatment was done by ground application, with most areas requiring five treatment sessions for complete control and to prevent seed set. Roseburg Forest Products supplied some contract labor. The Cow Creek Band of Umpqua Tribe of Indians contributed funds for some contract labor, while DCSWCD helped with contract administration.
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| Central Oregon orange hawkweed |
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In September 2005 a new detection of orange hawkweed, Hieracium aurantiacum, a state “A” listed noxious weed, was found being sold at a nursery in Deschutes County. Oregon Department of Agriculture staff confiscated and destroyed 157 orange hawkweed plants. ODA staff worked with the nursery, which was very cooperative in resolving the issue.
Program staff developed and distributed a noxious weed alert sheet on orange hawkweed and this was distributed to cooperators through our weed list serves and through a letter and mailing to all the nursery producers and retailers throughout Oregon. There was also a newspaper article in the Bend paper that generated 16 calls from private landowners who thought that they could have orange hawkweed in their ornamental plantings. Through site visits, program staff confirmed 12 new orange hawkweed sites in the Bend area. Some treatment was done on these sites during the fall and additional monitoring and follow up is scheduled for 2006.
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| Yellow floating heart |
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Yellow floating heart, Nymphoides peltata, is an ornamental pond plant. The first wild population was reported in 2004 in a pond adjacent to Fanno Creek in Washington County and was listed as an “A” weed by the OSWB in 2005. The Washington county site was treated in late summer. Fall monitoring showed re-growth and indicated a need for additional treatment for 2006. A second site was detected in 2005 near Springfield in Lane County. A treatment plan for the site will be implemented in 2006.
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| Giant hogweed |
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Giant Hogweed, Heracleum mantegazzianum, is an Oregon state “A” listed noxious weed, a federal listed noxious weed, and is on the western region CAPS pest list. Hogweed is a human health concern; the sap is highly toxic and the plant is also invasive in natural areas and can be a pest in agricultural and recreation areas. Giant hogweed survey and treatment continued for 2005 with the assistance of USDA funding. Five new sites were found this field season, four occurring in the north Willamette Valley around Portland and one in Polk County.
All 53 previously known sites (70 properties) were monitored and received chemical or mechanical treatment. Two areas received a high degree of attention in 2005 for survey efforts. Fanno Creek, a tributary of the Tualatin River was intensively surveyed and delimited in June 2005. 3500+ plants were found along the surveyed section, mostly seedlings. No plants were found along the Tualatin River. The plants that were found were treated with herbicide; no seed heads were present. A follow-up treatment was performed in late September. The second area of focus was survey efforts in Polk County. The first Polk County site was detected in June 2005 by a county road. Over 3100 acres were surveyed in Polk County with a focus on the area around the infestation; no additional sites were found.
An early detection survey was completed for 2005. The project provided a comprehensive survey to delimit previously known sites in western Oregon. With active and passive survey methods, additional areas in western Oregon were also surveyed. ODA consulted with cooperators, and provided outreach and technical assistance to private landowners. Land managers and private landowners were provided technical support to treat the known hogweed populations. A limited number of herbicide treatments were implemented by ODA to control and contain priority infestations. Technical bulletins and pest alerts were distributed and articles on giant hogweed were published in newspapers while the plant was in its most prominent growth stage. A presentation for garden clubs and other interested parties was developed and talks are being scheduled for spring 2006.
Chart: Giant hogweed: New sites reported by year
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| Kudzu |
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In July 2000, kudzu, Pueraria lobata, was detected on a road bank in Clackamas County. This was the first infestation detected west of Texas. Kudzu is an aggressive climbing vine that smothers other plants. It is a native of China and Japan and is a major problem in the southeastern US where an estimated seven million acres are infested. In August 2000, the second kudzu site for Oregon was detected in Multnomah County, and in June 2001, a third site was detected in Multnomah County. All sites were initially treated with the selective herbicide clopyralid, which is very effective for kudzu control.
Survey and detection efforts were conducted throughout western Oregon during 2005 and no new sites were detected. All three known sites were monitored throughout the 2005 season and one will require follow-up treatment in 2006.
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| Spartina survey and treatment |
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Ken French, ODA and Venessa Howard, PSU survey area near Coos Bay for Spartina alterniflora (tagged by ribbon)
Two occurrences of Spartina alterniflora were confirmed this summer. One site was regrowth from a historic site in Florence and a new site was detected in Coos Bay. ODA crews also worked with TNC to compete the covering of the large Spartina patens meadow and small outlying patches on Cox Island in Siuslaw Bay, Florence.
The historic S. alterniflora site known from Siuslaw Bay near the Port of Florence was first identified in 1990 and controlled by 1994. Subsequent monitoring found no regrowth until July 2005. The infestation was small and plants were removed by digging. The second S. alterniflora site was detected in June 2005 just east of the Charleston marina in Coos Bay. A follow-up investigation indicated unintended transplant of the Spartina from the Florence site to Charleston with native plugs dug for an ODOT mitigation project in Coos Bay. A comprehensive survey by helicopter, boat, and ground found no additional populations in Coos Bay. S. patens, known to exist on the Cox Island since the 1930s, is currently under management by The Nature Conservancy. The site is receiving active treatment by TNC and will require ongoing treatments to control the population.
During 2005 additional comprehensive surveys of Oregon estuaries for Spartina were completed and no additional sites were detected. This survey and detection effort is a primary goal identified in the Spartina Response Plan that was completed in 2003. Four exotic, invasive species of Spartina spp. (cordgrass) have been present in estuarine areas of the US west coast for over a century. During this time, they have significantly altered estuarine habitat and continue to pose threats to native wildlife and human commercial and recreational interests. The response plan provides historical and current information on West Coast populations of Spartina, reviews the biology of this group, and lays out a comprehensive, coordinated process to prevent, detect, identify, and treat this invasive weed. The plan identifies ODA as the lead agency in this effort, with other state and federal agencies providing assistance as needed.
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| Plumeless thistle |
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Plumeless thistle, Cirsium acanthoides, was known to exist only at one site in Fox Valley (Grant County) prior to 2004. In 2004 new sites were found prompting ODA to take a lead in the project. As a result of these expanded infestations, ODA staff undertook an intensive survey of much of Fox Valley and alerted landowners of the expanding population. Plumeless thistle was found and treated on 0.8 acres scattered over 1,200 acres in the south end of Fox Valley and four very small populations in the north valley on five private ranch properties. John George, Grant County Weed Control, and ODA attempted to regain the upper hand in the battle with Plumeless thistle in Grant County in 2004. Some 50 acres were treated on six ownerships. John left the program in late fall of 2004 and Shannon Springer took over. In 2005, Grant County made the spring treatment at all of the sites treated in 2004. ODA joined with Grant County to cover the affected area when the plants were easily identifiable. The 2004 treatment was very effective, with rosette numbers being markedly reduced. Treated acreage was not reduced much because the thistle rosettes were scattered and mixed with other thistles in many sites. Landowner interest and cooperation is high in Fox Valley with many of the new sites coming from local ranchers. Grant County Weed Control staff has changed again this fall. ODA will be partnering with the new Weed Staff, Tom Rush, to ensure that Plumeless thistle remains contained in Oregon.
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| Squarrose knapweed |
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Squarrose knapweed, Centaurea virgata, has been found at five locations in Oregon in the past. The largest site is near Long Creek in Grant County, in good quality bunchgrass range on three private ranches. This site has been under intensive treatment since the late 1980s to contain the spread and reduce the infestation. During the 2005 field season the containment area was intensively surveyed to find and treat existing plants. The 2004 treatment was very successful yielding a reduction from 15 acres treated in 2004 to three acres in 2005. Grant County performed the summer survey under ODA direction picking up outlier populations and skips at the Long Creek site.
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| Special projects for 2005 |
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The weed control program works on a variety of special projects and with a host of public and private cooperators to implement noxious weed control projects around the state. The following are a few of the projects completed in 2005.
Blackberry rust survey
In spring 2005, an exotic pathogen that attacks Himalayan blackberry was detected in Curry and Coos counties by ODA weed specialist Ken French. After consultation with state and federal pathologists, the pathogen was identified as Phragmidium violaceum. This is the rust that has been used in Australia and Chile as a biological control agent for wild infestations of blackberries (Rubus fruticosus group). Earlier this year, the pathogen was also detected in New Zealand, where it arrived as an unapproved adventive natural enemy. In Oregon, it has been found to occur on two species of blackberry, Himalayan (Rubus procerus, = R. armeniacus, = R. discolor) and on a thornless variety of evergreen blackberry (R. laciniatus). No one knows how the rust arrived in Oregon, or when, but it is suspected to have been around for at least two years. The rust has been found in all western counties of Oregon except Jackson and Josephine. It has been found in Washington and recently as far as 300 miles south of the Oregon boarder in California. The rust can cause die-back on blackberries and severely reduce fruit set. Affected vines have shriveled leaves covered on the underside with orange rust pustules that rain a yellowish-orange powder when disturbed. It is expected that the rust will be widespread by next year, as spores are spread by the wind throughout western Oregon. The full economic and ecological impacts are not yet known. Scientists at OSU are working with caneberry producers to find fungicides to help protect the evergreen blackberry crop. This pathogen is not an approved agent for biological control of blackberry and it should not be moved around because of the risk to native Rubus and crop species. In Australia, susceptible varieties of the weedy blackberry were reduced 50 percent after several years of exposure to the rust fungus. However, resistant varieties required the introduction of additional strains of the rust to provide additional control. (See related article in the Plant Health Section).
Japanese and giant knotweed survey and control
Members of the Polygonum family, giant and Japanese knotweeds, Polygonum cuspidatum, P. sachalinense, are tall plants that form clonal patches excluding other vegetation. Most invasive in riparian areas, the species establishes along streams and rivers and can overtake native and desirable streamside vegetation through aggressive growth and dominating height.
In western Oregon the knotweeds are established in many watersheds and threaten to invade new areas of healthy riparian communities or newly restored sites. East of the Cascades, Japanese and giant knotweed are uncommon and invading only a few riparian sites. ODA is approaching knotweed control from a watershed and regional approach focusing on outlying populations as a priority. In western Oregon, ODA is working with cooperators to provide technical assistance, implement watershed surveys and create demonstration control projects with the primary emphasis on identifying high priority watersheds and areas of control. In eastern Oregon, the knotweeds are being treated as new invaders to the region. ODA is assisting by increasing awareness with state and federal cooperators, county programs, and cooperative weed management areas (CWMAs). ODA is implementing or providing assistance for early detection surveys and treatment projects. State and private funds are assisting ODA in partnering with land managers and have helped leverage Resource Advisory Counsel funding, Oregon State Weed Board grants, and Oregon Watershed Enhancement Board grants to implement knotweed projects.
Lists of eastern and western Oregon knotweed projects in 2005
Eastern Oregon
- Knotweed Early Detection & Treatment
- Hell Canyon Survey and Project Plan Development
- Mitchell Oregon Knotweed Treatment
- Homestead Survey and Treatment
- Tri-County WMA Knotweed Treatment
Western Oregon
- Knotweed project to assist county programs, SWCDs, watershed groups and CWMAs in knotweed control.
- NOIWMP Western Oregon Knotweed Awareness, Survey and Treatment
- Linn County Knotweed Survey and Treatment
- Clatsop County SWCD Knotweed Demonstration and Treatment
- Crabtree Knotweed Multi-agency and Private Timberland Treatment
- Middle Fork of the Willamette Knotweed Survey and Treatment
- Nelson Creek/State Lands Knotweed Treatment
- Columbia County Working Group Knotweed Control
- Mid-Coast CWMA Knotweed Survey and Treatment
- Coos River Watershed Council Knotweed Control
Owyhee River Whitetop/Perennial Pepperweed Treatment
White top, Lepidium draba and L. appelianum, and more recently perennial pepperweed, Lepidium latifolium, have been targets of treatment along the lower reach of the wild and scenic Owyhee River from just above Rome to near the upper end of Owyhee Reservoir, below Birch Creek. The majority of the treatments are completed in and adjacent to areas on the river that are accessible by foot and ATV. The number of river miles covered each year are expanded by hiking up and down river from access points using backpack sprayers for treatment. In addition a stretch from Ryegrass down to Bogus landing has been floated, allowing treatment to a significant amount of the most heavily infested river corridor. This combination of techniques allows treatment of virtually everything except 10 river miles from Sand Spring to Hole in the Ground. These treatments have been coordinated by ODA and have involved BLM contractors. Several other invaders are being treated as encountered. These include Scotch thistle, Onopordum acanthium, Musk thistle, Carduus nutans, Saltcedar, Tamarix ramosissima, and Russian knapweed, Acroptilon repens.
The river level during the optimum treatment time for white top is usually lower than floaters prefer. This usually occurs after Memorial Day, which is the usual end of the recreational float season on the Owyhee. This year early warm temperatures brought white top into bloom earlier and unseasonable rain in May brought the river level up. The Owyhee was attracting a lot of float traffic and the weeds were ready for treatment prior to Memorial Day. There was some concern about interaction with recreational floaters and sprayers so we tried to maintain a low profile. It was very pleasant to find that everyone we spoke to, whether on the river or when working near camps, was very supportive of our efforts to hold the line on invasive plants. Unfortunately, some of our sites, particularly of Pepperweed, were submerged. The river was high enough to allow floating the stretch from Ryegrass to Bogus, and treating the remains of the heavily infested area there. In 2005, 3.7 net acres were treated over a 775 total acres treatment area.
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| Weedmapper |
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WeedMapper (www.weedmapper.org) is a Web site that provides distribution maps of all state-listed weeds in Oregon, as well as, information on the identification and impacts of those weeds. It also provides a weed sighting report form to allow land managers to notify ODA quickly and easily of a new weed sighting. The Web site is a joint project of the Oregon Department of Agriculture and Oregon State University.
In May 2005 a redesign of an earlier version of the Web site was launched, allowing maps to be accessed by any type of computer. Weeds are mapped at the state and county levels. In December 2005 the final set of map pages were completed; these maps will be updated yearly.
Weed maps are shown at two different resolutions depending on the availability of specific weed location data: when GPS data is plentiful, maps are produced with each weed location pinpointed with a red dot; when GPS data is scarce, more general state distribution maps are used that show the abundance of a weed by county. Noxious Weed Control Program Staff provided the distribution information for the counties in their respective areas.
GPS data is accepted from many different cooperators. Currently WeedMapper maps are compiled from data from ODA, USFS, BLM, county weed programs, SWCDs, cities and non-profit groups such as weed working groups. Cooperative Weed Management Areas are anticipated to provide additional information in the future. Data will also be accepted from the weed sighting report form after it is reviewed for completeness and reliability.
In November 2005 a presentation on WeedMapper was given at the Oregon Vegetation Management Association conference and a call for data was sent through the Oregon weed list-serve. Offers of data soon followed.
The response to the launch of WeedMapper has been overwhelmingly positive. Land managers report that it is a valuable tool and are eager to assist in its development by sharing what information they have.
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| Biological control |
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Since 1947, 72 species of classical biological control agents have been introduced against 27 species of noxious weeds. Several of these biocontrol agents have become reassociated with six additional species of weeds for which they were not originally introduced. ODA manages over 110 biocontrol projects (weed/agent combinations), the most of any state in the US. The ODA biocontrol database contains more than 11,400 records of biocontrol agent releases. Several biocontrol projects have been successful in controlling targeted weeds, including tansy ragwort, St. Johnswort, musk thistle, Mediterranean sage, purple loosestrife, yellow starthistle, and diffuse knapweed, especially at sites that are managed to improve competitive vegetation. ODA strives to adhere to the International Code of Best Practices for classical biological control of weeds in order to better implement a safer and more effective biocontrol program.
Cumulative number of weeds targeted and cumulative number of classical biological control agents released in Oregon by decade.
New releases and recoveries
Rush skeletonweed The root boring moth Bradyrrhoa gilveolella was released in the Rivergate District of Multnomah County. This was the first release in Oregon. A batch of 200 eggs was transferred to plants in the field. The Nez Perce Biocontrol Center and University of Idaho provided laboratory stock for this experimental release to determine if the moth can adapt to plants and climate in Western Oregon. Additional releases (if available) will be made in 2006. Salt cedar
The leaf beetle Diorhabda elongata was released in 2003 for the first time in Oregon. An experimental field cage release was made near Adrian, Malheur County, in conjunction with Dr. Tom Dudley, USDA-ARS. ODA agronomist Dan Sharratt is monitoring the project in cooperation with USDA-APHIS and BLM. The beetles were recovered in the cage in 2004, but a severe flash flood in late summer destroyed the colony. Three additional releases were made in Malheur County in August of 2005, after meeting extensive pre-monitoring requirements set by US Fish and Wildlife Service. Additional releases from Lovelock, Nevada are planned for 2006.
Significant accomplishments
Biological agents were released at more than 108 sites in Oregon during 2005. Over 143 biocontrol sites were monitored to determine establishment and impact of biocontrol agents. The USDA biocontrol program, under the direction of Gary Brown, remains a very important partner in implementing biocontrol in Oregon. ODA and USDA typically supply surplus biocontrol agents to many local agencies and other states. The ODA program continues to work on cooperative research projects with Dr. Jeff Miller and Dr. Peter McEvoy and his staff at Oregon State University. The ODA biocontrol program also serves as the state level biological control of weeds data center for the US.
Dalmatian toadflax
The stem-boring weevil, Mecinus janthinus, has been recovered in several counties. This promising bioagent caused significant stand reductions at several sites in Oregon in 2005. Collection for redistribution in Oregon is expected to begin in 2006 and continue for several years.
Knapweeds
Large-scale collection and redistribution of the seed head weevils, Larinus minutus, L. obtusus, and Bangasternus fausti, have been made throughout Oregon on diffuse, spotted, and meadow knapweeds. The weevils have caused declines in diffuse knapweed density at several sites near Heppner and The Dalles. Despite resurgences associated with late rainfall at numerous sites in 2005, improved control is expected. The root boring moth Pterolonche inspersa was rediscovered near Mosier in 2005. The moth has been undetectable during the past five years. Additional research on collection and redistribution is planned for 2006.
Knotweed
Prelease studies on Japanese knotweed and its allies were initiated at several sites in Oregon in cooperation with ODA. This study is necessary before any new agents can be released in Oregon. It was conducted by Dr. Fritzi Grevstad, University of Washington, funded by USFS, and is expected to continue in 2006. Meadow knapweed
Experimental releases of the spotted knapweed seedhead weevil, Larinus obtusus, in 2001 proved successful in Douglas County. We began a cooperative program with OSU, USFS, and BLM, targeting meadow knapweed in western Oregon. Over 100 releases were made during the past four years. This is the first biocontrol agent that has shown any promise against this weed. The weevil was recovered for the first time in the Willamette valley in 2004.
Mediterranean sage
An ongoing cooperative study with Dr. Jeff Miller, OSU Department of Range Science, is studying the regional long-term impacts of the root/crown weevil Phrydiuchus tau. Many ODA release sites from 1970-1983 have shown significant control at sites now dominated by perennial grasses and shrubs. Results from regional studies will be submitted for publication in 2006.
Purple loosestrife
The Galerucella leaf beetles have reduced numerous infestations of purple loosestrife throughout Oregon by more than 90 percent. Cooperative biocontrol projects continued with USDA staff and Dr. Peter McEvoy of OSU to monitor and redistribute the biocontrol agents throughout the lower Columbia River area. Many purple loosestrife stands are declining following severe defoliation by the leaf beetles. A 10 acre stand of loosestrife was completely defoliated by leaf beetles within a few weeks at Horseshoe Lake, in Marion County. Tens of thousands of surplus beetles were provided to other states.
Tansy ragwort
In 2005, numerous sites in the Willamette Valley experienced a resurgence of tansy ragwort, especially in Marion County. Biocontrol agents were found at all of the recalcitrant infestations. Fewer ragwort rosettes were observed during fall of 2005, therefore the severe local outbreaks are expected to be short-lived. No livestock deaths associated with the 2005 outbreak have been reported to ODA.
Staff Entomologist, Eric Coombs, served as chief editor of Biological Control of Invasive Plants in the United States and authored several chapters, therein. It was published in late 2004. The Weed Program provided copies to numerous cooperators in 2005 as part of Weed Awareness Week.
Economic benefits
Classical biological control of weeds has a good safety record, but a somewhat scanty track record of documented economic benefits. Most of the funding for biocontrol projects is utilized during the foreign exploration, host specificity testing, and introduction phases, with little appropriated for long term efficacy studies. Reported benefit-cost ratios from around the world vary from 112:1 to 2:1. Biocontrol of tansy ragwort in Oregon yielded an 85 percent internal rate of return and a 15:1 benefit-cost ratio. On successful long-term projects, benefits can occur as steady stream returns, i.e., $5 million/ year for the ragwort project in Oregon, where annual agency expenditures on this weed are now less than $20,000 per year.
Where feasible, it is economically advantageous to implement biocontrol in order to reduce annual losses. By actively redistributing ragwort biocontrol agents, ODA accomplished a successful regional project 5-10 years sooner than by the natural spread of the insects, averting $25-$50 million in losses to agriculture.
A partially successful biocontrol project, i.e., one that reduces weed infestations by variable percentages over large areas, can provide a positive benefit-cost ratio, even though the degree of weed control may be less than desired. If biocontrol in Oregon reduced the top 12 weeds by 30 percent, annual losses could decrease by $20 million.
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