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

Biological Control

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.

Bear Trap Success Story

Wednesday, June 23rd, 2010

In April of 2001 a float trip down the Madison River was conducted involving members of the BLM, the Montana Wilderness society, Madison County, U.S. Forest Service, the Greater Yellowstone Coalition, Gallatin County and other interested individuals. They determined that due to the size, density and location of the current infestations, that eradication was no longer an option but that a long term plan of control and containment would be more practical and cost effective. With members of the original group plus a Dow AgroSciences representative and others knowledgeable in noxious weed control a second float trip was conducted in August to help devise a plan of action.

Weed control was initiated in the fall of 2001 using both biological agents and herbicide. The biological control was released in the more inaccessible areas above the river and above the hiking trails, while herbicide was used along the trails and from the trails to the river, where public use is the highest. Herbicide application was done as a joint effort between the BLM and the Madison County Weed Board with joint spray days being held twice yearly, one in the spring and the other in the fall. After the first year of treatment we were surprised at how the native grasses came back and became fairly competitive with the knapweed. In 2002, 2003, and 2004 a private contractor treated the road leading into the trailhead and any of the trails that couldn’t be covered during the joint spray days. Starting in 2005 the BLM hired a crew of two sprayers that would take over the role of the private contractor. A minimum of three float trips a year were scheduled in order to gain access to some infestations of Leafy Spurge that are inaccessible by land.

To date the project has met with great success. The size and density of the noxious weed infestations has been reduced dramatically with the only problem being the re-infestation of some of the treated areas by cheatgrass. Beginning in 2010 we hope to get the original group together again to determine what our strategy for the next ten years will be and how we will handle the re-vegetation of some of the areas infested by cheatgrass.

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.

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.

Full Article Text

Biocontrol Work Group Minutes

Thursday, April 30th, 2009

2009

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