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

Integrated Weed Management Articles

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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Turning Livestock into Land Management Tools at Grant-Kohrs Ranch National Historic Site

Sunday, November 29th, 2009

by Christina Miller,
Natural Resources Specialist, DSC Socks, Spackle, and Ginger Snap are only a few of the newest weed control managers at Grant-Kohrs Ranch NHS. They successfully completed a seven-step program that modified their preferred cuisine and made them effective rangeland stewards. These new weed control managers dutifully spend their days grazing in the pastures, working toward the eradication of exotic invasive weeds. Oh, by the way, they’re cattle, affectionately termed “smart cows.”

Read the complete article about these weed eating cattle.

An Overview of Targeted Grazing and the Montana Sheep Institute

Thursday, November 12th, 2009

By Becky Kington, Montana Weed Control Association Executive Director and Dr. Lisa Surber, Research Scientist, Montana Sheep Institute.

The following is an interview that was conducted on October 23, 2009, between Becky and Lisa regarding targeted grazing.

Sheep grazing dalmatian toadflax, photo credit: L. Surber

Sheep grazing dalmatian toadflax, photo credit: L. Surber

Lisa, the MSU Sheep Institute has been involved in numerous targeted grazing projects in Montana over the past few years, and I have to credit MSI with elevating targeted grazing as an integrated control method for noxious weeds. How many targeted grazing projects have you [MSI] been involved with over the years and what specific weeds have been chosen to experiment with?

The Montana Sheep Institute (MSI) oversees approximately 15 targeted grazing projects with monitoring sites utilizing sheep and goats from multiple sheep producers.  Montana Sheep Institute weed projects directly involved over 50,000 acres of weed-infested Montana rangeland and about 500 landowners. Currently major weed projects are targeted at leafy spurge, spotted knapweed and Dalmatian toadflax.

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What chemical do I use for my noxious weeds?

Friday, October 23rd, 2009

Again, because of the variety of herbicide available, differing soil conditions, and because of a variety of environmental conditions, it is best that you contact your weed professional(s) to properly assess your weeds and identify the best options for your specific environment.

Got Weeds? These Sheep Will Make House Calls

Friday, October 23rd, 2009

MISSOULA, Mont. — Chilled by an autumn wind, Enrique Marquez watched from horseback as the sheep gamboled down the mountain. A border collie nipped the heels of wayward ewes. All summer and into the fall, the flock grazed on noxious weeds infesting about 1,000 acres of public lands above the Missoula Valley as part of this city’s effort to restore its native prairie grasses.

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Biological Control Monitoring Project

Friday, October 23rd, 2009

The USDA-APHIS-PPQ, MT Dept. of Ag, and the Bureau of Land Management have developed a biological control monitoring project. Find out how you might become part of the project.

Biological control agents for several of Montana’s most widespread noxious weeds have been released across the state for the past 30 years. Although there have been many successes, there are many things we still do not know about these insects that we have been releasing. For a land manager, one of the most important things to know is if these species are affecting the weed populations like we hoped and if so, where can I get some.

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Rehabilitation of Weed-Infested Rangeland

Friday, October 23rd, 2009

by James S. Jacobs, Michael F. Carpinelli and Roger L. Sheley*

URRENT weed management efforts often focus on controlling weeds, with limited regard to the existing or resulting plant community. Because of environmental, ecological and economic concerns, the appropriateness and effectiveness of rangeland weed management practices are being questioned. It has become clear that weed management decisions must consider these concerns. The development of future weed management practices must be based on our understanding of the biology and ecology of rangeland ecosystems.

Land use objectives must be developed before rangeland weed management plans can be designed. This implies that strictly killing weeds is an inadequate objective, especially for large-scale infestations. Instead, a generalized objective could be to develop a healthy plant community that is relatively weed-resistant while meeting other land-use objectives such as forage production, wildlife habitat development or recreational land maintenance.

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Revegetation Guidelines for Western Montana: Considering Invasive Weeds

Friday, October 23rd, 2009

Major portions of western Montana’s landscape become degraded and disturbed every day. Disturbances can be natural, such as floods and fires, or strictly human-induced, such as roads and construction sites, utility line trenches, or improper grazing. These disturbed areas may recover naturally, but in some cases it may be many years before desired plants become established or recover. Conversely, some areas may never naturally recover because invasive weeds may establish first and prevent native plants from establishing, growing, and reseeding. Furthermore, invasive weeds can potentially spread into adjacent, healthy landscapes where they threaten local biodiversity, alter nutrient and water cycling, diminish wildlife and livestock forage, and increase soil erosion and stream sedimentation.

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