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

Centaurea maculosa

MSU Report for the Montana Noxious Weed Trust Fund Advisory Council

Wednesday, June 19th, 2013


This report for the Montana Noxious Weed Management Advisory Council was assembled in compliance with the Montana Noxious Weed Trust Fund Act and Administrative Rules which require an annual report from the Montana Agricultural Experiment Station and Montana State University Extension Service on current projects and future plans. This report is a compilation of major weed science research and education activities conducted by MSU over the past three years and includes highlights of funded Montana Noxious Weed Trust Fund grants as well as comprehensive reporting of all weed science research products and education funding and activities.

Montana Noxious Weed Trust Fund Projects 2010–2012

  • Biological Control of Common Tansy and Oxeye Daisy, Jeff Littlefield
  • Biological Control of Invasive Hawkweed and Tansy Ragwort, Jeff Littlefield
  • Biological Control of Russian Knapweed, Jeff Littlefield
  • Biological Control of Whitetop and Perennial Pepperweed,Jeff Littlefield
  • Can Biological Control and Targeted Sheep Grazing be Integrated to Suppress Spotted Knapweed?, Jeff Mosley
  • Cheatgrass Ecology and Integrated Management, Jane Mangold
  • Continental Divide Invasive Weed Barrier Zone, Kim Goodwin
  • Establishing and Monitoring Insectaries for Yellow Toadflax Biocontrol, David Weaver
  • Herbicide Resistance Extension Information for Montana Producers, William Dyer
  • Identifying and Testing Candidate Agents for Russian Olive Biocontrol, David Weaver
  • Implementing EDRR in Montana Using the INVADERS Database, Jane Mangold
  • Integration of Pathogens, Sheep, and Herbicides to Manage Cheatgrass, Fabian Menalled
  • Missouri River Watershed Coalition Coordination, Elizabeth Galli-Noble
  • Rangeland Revegetation Revisited, Jane Mangold        Saltcedar Effects on Mycorrhizal Fungal Communities and Screening of Native Species for Restoration, Erik Lehnhoff
  • Tall Buttercup Ecology and Integrated Management, Jane Mangold
  • Weed Free Borders Protection Program, Kim Goodwin
  • Weed Management Certification Program, Jane Mangold
  • Weed Seedling Identification Guide, Jane Mangold

Download a copy of the complete report 2013 MSU Annual Report to the MNWTF

Many Kinds of Knapweed Found in Montana

Friday, September 2nd, 2011


The September MSU monthly weed post focuses on knapweeds.  Did you know that there are eight kinds of knapweed found in Montana?   Dr. Jane Mangold’s publication this month takes the flower of each of the knapweeds and teaches us how to tell the difference.

Download this two page publication today.   Learn how to tell spotted knapweed from brown knapweed.

MWCA has pages devoted to identification of the knapweeds  listed on the Montana Noxious Weed list:  Russian Knapweed, Spotted Knapweed, Diffuse Knapweed and Yellow Starthistle.

Weed of the Week – Spotted Knapweed

Thursday, August 26th, 2010


Notice the dark spots on the bracts under the blossom, this is where the weed gets its name Spotted Knapweed.

Notice the dark spots on the bracts under the blossom, this is where the weed gets its name Spotted Knapweed.

Introduction Spotted knapweed is the number one problem on rangelands in western Montana.  Spotted knapweed is dramatically interfering with the Montana’s unique ecosystems.  It was accidentally introduced to the United States through contaminated alfalfa and contaminated soil used as ship ballast.

The first report of this weed in Ravalli County was 1921.  Knapweed has infested 2-5 million acres in Montana, with potential to spread to the 34 million susceptible acres in the state.  Spotted knapweed has been recorded in every county in Montana.

Concerns Knapweed has changed the face of our lands in western Montana.  Ranchers, wildlife enthusiast, hunters, foresters, hikers, and fisherman are impacted by the dramatic affect that knapweed is having on our ecosystem.  Spotted knapweed is particularly hard to manage due to its ability to occupy a variety of sites and habitats.  This weed will aggressively out-compete native vegetation.

Watersheds throughout the state are reaping the negative effects of the soil erosion that knapweed causes.  The soil erosion caused by spotted knapweed is degrading fisheries and water quality.  Spotted knapweed is impacting Montana’s economy in a serious way. The negative effect knapweed has on Montana’s economy is an estimated $42 million annually.

Identification Spotted knapweed is a pinkish-purple flower and the plant grows 1-3 feet tall.  The bracts underneath the flowers have dark spotted tips that are also fringed.  Spotted knapweed blooms from mid to late July and through September.  Each individual flower will bloom for 2-6 days.  The flowers will reopen after 20 days to disperse seeds.  One knapweed plant can produce up to 1000 seeds and remain viable in the soil for 8 years. You will begin to see spotted knapweed rosettes in early April.  Knapweed can grow to nearly 4 feet tall on moist sites.

What can you do? For pastures and rangelands that have not been infested, prevention is key.  Avoid transporting seeds from infested sites.  Seeds can attach themselves to vehicles, clothes, and animals.  Use only certified weed-seed free seed and hay in non-infested areas.  For infested areas integrated weed management methods need to be employed.  Small infestations can be controlled through timed hand pulling, which should take place when the soil is moist and prior to the plant going to seed.  Pulled plants should be bagged and disposed of or burned.

Plowing an infested area is feasible, if plowed down to 7 inches below soil surface and if the area is reseeded with desirable vegetation.  Plowing may cause dormant knapweed seeds in the soil to germinate.  This method is best if used with herbicide treatment or grazing.  Sheep, goats, and cattle will graze spotted knapweed at certain times.  Grazing on knapweed should be timed for when the grasses have gone dormant.  Sheep grazing in combination with herbicide use can be fairly effective.  There are multiple insects that exist in Montana as a mean of controlling knapweed.  The success of knapweed eradication requires a long-term commitment.

Visit the MWCA Weed ID pages for additional information and pictures of spotted knapweed.

This series of articles was developed by Ravalli County.  If you would like to use these articles please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.

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.

Download a copy of the research article.

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.

Download a copy of the research article.

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.

Click here to download and read the complete article.

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.