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.
2010 Statewide Biological Control Monitoring Report
Thursday, October 21st, 2010Compatibility of Seed Head Biological Control Agents and Mowing for Management of Spotted Knapweed
Monday, April 5th, 2010Authors: 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, 2010Complete 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
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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, 2010Full 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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Biological Control Monitoring Project
Friday, October 23rd, 2009The 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.