Working together to strengthen and support noxious weed management efforts in Montana.

Research Information

Growth inhibition of Dalmatian toadflax, Linaria dalmatica (L.) Miller, in response to herbivory by the biological control agent Meeinus janthinus Germar

Tuesday, July 26th, 2011


Abstract:  Our study reports the results of field and garden experiments designed to quantitatively evaluate the impact of herbivory by a weed biological control agent, the stem-mining weevil Mecinus janthinus Germar, on the growth of its exotic host Dalmatian toadflax, Linaria dalmatica (L.) Miller. Herbivory by M. janthinus under both natural and manipulated environmental conditions inhibited L. dalmatica growth. Reductions in stem length, biomass, and growth were more pronounced for plants subjected to both exophagous (adult) and endophagous (larval) feeding injury than for plants exposed only to adult folivory. Decreases we observed in root biomass could additionally inhibit shoot production from lateral roots. This provides a plausible mechanism explaining anecdotal reports correlating the reduced spread of L. dalmatica with attack by M. janthinus. Our results indicate that L. dalmatica growth is compromised once a threshold density equivalent to 5 M. janthinus larvae per stem is exceeded. The consistency of growth responses observed in this study suggests that a mechanistic/quantitative approach, such as measuring the impact of M. janthinus herbivory on L. dalmatica, is a robust and relevant method for postrelease evaluations of weed biocontrol efficacy.

Authors: Schat, Marjolein; Sing, Sharlene E.; Peterson, Robert K. D.; Menalled, Fabian D.; Weaver, David K.

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Assessing Environmental Risks for Established Invasive Weeds: Dalmatian (Linaria dalmatica) and Yellow (L. vulgaris) Toadflax in North America

Tuesday, July 26th, 2011


Abstract: Environmental risk assessments characterizing potential environmental impacts of exotic weeds are more abundant and comprehensive for potential or new invaders than for widespread and well-established species such as Dalmatian (Linaria dalmatica [L.] Mill.) and yellow (L. vulgaris Mill.) toadflax. Specific effects evaluated in our assessment of environmental risks posed by yellow and Dalmatian toadflax included competitive displacement of other plant species, reservoirs of plant disease, animal and insect use, animal toxicity, human toxicity and allergenicity, erosion, and wildfire. Effect and exposure uncertainties for potential impacts of toadflax on human and ecological receptors were rated. Using publicly available information we were able to characterize ecological and human health impacts associated with toadflax, and to identify specific data gaps contributing to a high uncertainty of risk. Evidence supporting perceived negative environmental impacts of invasive toadflax was scarce.

Authors: Sing, Sharlene E.; Peterson, Robert K. D.

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Research Report on Biological Control of the Russian Olive

Tuesday, May 31st, 2011



Russian olive, Elaeagnus angustifolia, is a shrub or small tree of Eurasian origin.  It was originally planted in North America as a horticultural plant but has started escaping from cultivation and invading riparian and other moist habitats in western North America. This report summarizes the results of investigations carried out in 2010 on the biology, host specificity and impact of potential biological control agents of Russian olive. The investigations were conducted in close collaboration with the Biotechnology and Biological Control Agency (BBCA), Rome, Italy, the Uzbek Academy of Sciences, Tashkent, Uzbekistan, and the University of Mashhad, Iran.

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Taking the Pulse of Riparian Protection in Montana

Monday, April 18th, 2011


The Montana Association of Conservation Districts produced a 108 page report on riparian areas in Montana.   We have a copy of that report available for download.


What techniques are Montanans using to protect riparian areas? A broad spectrum of Montanans shared answers to this question at ten listening sessions and two focus groups held statewide between January and July 2010. Research and outreach through more than 60 personal interviews followed the listening sessions to flesh out more detailed profiles of instructive “best management practices” (BMPs).

This report is divided into three sections. Section I details the actual listening sessions. Section II makes recommendations for future actions. Section III provides rich details about individual practices through the use of case profiles.

Two hundred and twenty five people attended the listening sessions, spearheaded by the Montana Association of Conservation Districts and cosponsored by ten local Conservation Districts from Glendive to Corvallis. More than 92 techniques were described by individuals from agriculture, transportation, energy and public utilities, recreation, conservation, municipal and county governments, forestry, public land managers and small business. These results are reported in Section I of this document. More detailed notes from all listening sessions and focus groups can be found online at

Implications and recommendations are also addressed in Section I, which looks at what the project results suggest for possible future actions. Given what was learned, the following recommendations are made to advance riparian protection, including the use of riparian BMPs, in the future.

Recommendation A: Develop and Enhance Riparian Education, Outreach & Technical Assistance

Action Step 1: Catalyze and support local, community-specific riparian protection education, outreach and technical assistance.

Action Step 2: Develop innovative, popular media using current technology.

Recommendation B: Create Opportunities for Collaborative Problem-solving

Action Step 3: Identify and forge additional partnerships.

Action Step 4: Explore a new frontier of riparian BMPs—land development and the building industry

Action Step 5: Clarify specific permit challenges and identify a process to address these challenges.

Recommendation C: Research, Assess and Train for Effective BMPs

Action Step 6: Validate effective BMP practices.

Action Step 7: Identify effective BMP models for replicability.

Action Step 8: Train riparian restoration/protection professionals and develop standards for systematic installation of effective riparian BMPs.

Recommendation D: Understand and Maximize the Economic Benefits of Protecting Riparian Areas

Action Step 9: Review economic literature and incentive programs and perform technical cost-benefit analysis for public and private settings.

Action Step 10: Compile and disseminate economic benefit information through channels identified in Recommendations A, B and C.

Action Step 11: Explore feasibility of developing a cost benefit assessment tool for use in the field.

Deeper insights into BMP implementation were obtained through numerous interviews summarized in Section II of this report. These profiles enrich the impressionistic stories from the listening sessions by delving deeper into the motivations, the challenges, and the lessons learned from representative sectors of the population and economy. All told, this report “takes the pulse” of the present state of “riparian literacy” in Montana, providing a qualitative overview of techniques in use.

This document should be of particular interest to members of the Governor’s Task Force for Riparian Protection, the Montana Association of Conservation Districts, watershed groups, nongovernmental organizations (NGOs) and local, state and federal agencies involved in riparian protection. The profiles in Section III may be of interest to citizens from the sectors which are covered within—agriculture, education and outreach, streamside property owners, etc.

2010 Statewide Biological Control Monitoring Report

Thursday, October 21st, 2010


APHIS-PPQ completes a second season of the statewide biological control monitoring program in cooperation with Montana Dept. of Ag. and the BLM. Over the past two years, this project has been helping counties, state and federal agencies, and Indian Reservations with monitoring past biological control releases and assessing the potential for collectibility when they find established populations.  Download your copy of  the report for the work completed in 2010.

Compatibility of Seed Head Biological Control Agents and Mowing for Management of Spotted Knapweed

Monday, April 5th, 2010


Authors: Jim M. Story, Janelle G. Corn, and Linda J. White

Summary: Seed head insects, primarily the seed head fly, Urophora affinis, and the seed head weevils, Larinus spp., are reducing spotted knapweed seed production by about 94% in most areas of western Montana. Studies were conducted on the compatibility of seed head biological control agents and mowing for management of spotted knapweed.  Our study demonstrated that mowing of spotted knapweed in the spring and early summer can result in the growth of secondary flower buds which escape attack by seed head biocontrol agents, thereby allowing the knapweed to produce a nearly-normal complement of seed.  Therefore, we conclude that the historical practice of mowing spotted knapweed during the spring and early summer with no follow-up mowings should be avoided if large populations of seed head biocontrol agents are present.

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Influence of Seed Head-Attacking Biological Control Agents on Spotted Knapweed

Wednesday, March 24th, 2010


Complete Title: Influence of Seed Head-attacking Biological Control Agents on Spotted Knapweed Reproductive Potential in Western Montana over a 30-year Period

Authors: Jim M. Story, Lincoln Smith, Janelle G. Corn & Linda J. White

Summary:  Studies were conducted on the impact of seed head insects on spotted knapweed reproductive potential in western Montana over a 30-year period.  Results indicated that seed head insects are reducing seed production by about 94% in many areas of western Montana.  The reduction of knapweed seed production has resulted in a 98% reduction in the knapweed seed bank which, in turn, has contributed to the decline of knapweed in these areas.  Of the seed head insects, the fly, Urophora affinis, and the weevils, Larinus obtusus and L. minutus, are having the greatest impact on knapweed seed production.  The current decline of spotted knapweed in many areas is likely due to the impact of the seed head insects on the knapweed seed bank and the effects of the root weevil, Cyphocleonus achates, on mature plants.

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Decline of Spotted Knapweed Density in Montana with Large Populations of the Root Weevil

Monday, March 15th, 2010


Full Article Name: Decline of spotted knapweed density at two sites in western Montana with large populations of the introduced root weevil, Cyphocleonus achates (Fahraeus)

Authors: J.M. Story, N.W. Callan, J.G. Corn, L.J. White

Summary:  Spotted knapweed plant density was monitored over a 11-year period (1993-2004) at two sites in western Montana where the root weevil, Cyphocleonus achates was released.  Spotted knapweed density declined significantly over time at both sites (99% and 77%, respectively), after C. achates numbers increased dramatically at both sites.  The current decline of spotted knapweed in many areas is likely due to the effects of C. achates on mature knapweed plants and the impact of the seed head insects on the knapweed seed bank.

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New Research Summary & Expertise Summary Published

Thursday, March 4th, 2010


Rocky Mountain Research Station Invasive Species Work Group publishes a new research summary and expertise directory.

In the first paragraph it states:

“Rocky Mountain Research Station (RMRS) personnel have scientific expertise in widely ranging disciplines and conduct multidisciplinary research on invasive species issues with emphasis in terrestrial and aquatic habitats throughout the Interior West, Great Plains, and related areas  RMRS invasive species research covers an array of diverse ecological and environmental gradients, from southwestern deserts to northern temperate rain forests and from low-elevation plains and basins to alpine summits.”

The table of contents is as follows:

RMRS Invasive Species Research Program
Common themes of RMRS invasive species research
RMRS Invasive Species Research Priorities and Future Direction
Summary of Taxa-Specific Research
1. Plants
2. Pathogens
3. Insects
4. Aquatic Species
5. Terrestrial Vertebrates
Expertise Directory

Download your personal copy of this great reference here.

Transportation of Spotted Knapweed Seeds by Vehicles

Wednesday, January 27th, 2010


Vehicles have long been suspected of being a major distributor of spotted knapweed seed. The purpose of this experiment was to determine how many seeds could be disseminated by vehicles and to measure how far the seeds would travel.   Sites were chosen at the Story Hills in Bozeman, the old Milwaukee Road rail yard in Deer Lodge and a site near the Bauxendale Volunteer Fire Department west of Helena. At each site, twelve plots each measuring twelve by forty feet were staked and the surrounding area was mowed. A late model pickup  truck was driven 40 feet into each plot and backed out. The vehicle was then driven 25 mph for distances of 0, 0.1, 1.0, and 10.0 miles. The vehicle was placed on a large tarp and the entire undercarriage was vacuumed to collect spotted knapweed seeds and plant material. The collected material was bagged to await seed counting. At the Deer Lodge site, over 1633, 510, 226 and 138 seeds remained on the vehicle after traveling 0, 0.1, 1.0, and 10.0 miles. The results indicate that spotted knapweed seed is readily disseminated by motor  vehicles for long distances.

Prepared by:

Phil Trunkle and Pete Fay
Department of Plant and Soil Science
Montana State University
Bozeman, Montana 59717

Download a PDF version of this document here.