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Assessing the Impacts of Biological Control on Spotted Knapweed in Minnesota Natasha Northrop Minnesota Department of Agriculture Legislative Commission on Minnesota Resources (LCMR)
Spotted Knapweed, Centaurea stoebe L. ssp. micranthos (Gugler) Hayek (syn. =C. biebersteinii DC. )
Spotted Knapweed Infestation
Spotted Knapweed Biological Control Agents Agapeta zoegana Urophora quadrifasciata Cyphocleonus achates Larinus obtusus
LCMR* Research Project: Biological Control of Spotted Knapweed in Minnesota *Legislative Commission on Minnesota Resources, now called the Legislative-Citizen Commission on MN Resources (LCCMR)
Goals of SK Biocontrol Research - Increase MDA’s knowledge of spotted knapweed & biological control of this weed in Minnesota status of most release sites was unknown. - Define trends related to site characterizations that might affect biocontrol; define trends related to the invasiveness potentials of sites. - Determine control impacts of bioagents. - Develop protocols for future management decisions & best management practices.
Research Methods: 1) Obtain USDA-APHIS-PPQ Release, Monitor, & Harvest Biocontrol Records; combine with MDA Records (2004) 2) Characterize each biocontrol site (2004) a) visit each site once during growing season b) topography, soil type, ownership, land use, etc. c) delineate knapweed infestation area = acreage d) vegetation observations; % knapweed cover (est. ) e) bioagent presence (sweep netting) 3) Revisit 10 sites w/high bioagent recoveries/combos (2005) a) sample each site three times over growing season, more detailed vegetation sampling b) use random transect sampling within delineated infestation areas
Advanced Technology in the Field
2005 # knapweed Sampling Transect quadrate data= stems, ht. of 5 random stems, # rosettes, # flowers, # seed heads, % knapweed bloom, % cover (knapweed, other forbs, grasses, bare ground, etc. ) 1 transect = 1 m 2 quadrate drop + sweep set (25 sweeps) + 1 m 2 quadrate drop
Identified Biocontrol Release Sites with GPS Data
Bioagent Species and Releases in Minnesota, 1991 -2004 Biocontrol Agent Order Family Method of Damage to SK Released Agapeta zoegana Lepidoptera Cochylidae Root Borer (L) 1, 717 Bangasternus fausti Coleoptera Curculionidae Leaves/Rosettes (A), Seedhead (A/L) 2, 975 Chaetorellia acrolophi Diptera Tephritidae Seedhead (A/L) 1, 340 Cyphocleonus achates Coleoptera Curculionidae Leaves/Rosettes (A), Root Borer (L) 3, 745 Larinus minutus Coleoptera Curculionidae Leaves/Rosettes (A), Seedhead (A/L) 61, 646 Larinus obtusus Coleoptera Curculionidae Leaves/Rosettes (A), Seedhead (A/L) 3, 519 Metzneria paucipunctella Lepidoptera Gelechiidae Seedhead (A/L) 5, 470 Sphenoptera jugoslavica Coleoptera Buprestidae Leaves/Rosettes (A), Root Borer (L) 100 Terellia virens Diptera Tephritidae Seedhead (A/L) 600 Urophora affinis Diptera Tephritidae Seedhead (A/L) 108, 550 Urophora quadrifasciata Diptera Tephritidae Seedhead (A/L) 41, 400 Urophora spp. mix* Diptera Tephritidae Seedhead (A/L) 565, 663 (A)=Adult Stage (L)=Larval Stage Total: *Release consisting of mixtures of U. affinis and U. quadrifasciata. 796, 725
Peak Emergence Chart of Recovered Spotted Knapweed Bioagent Species at 10 Biocontrol Sites in MN, 2005
Obstacles to Drawing Solid Conclusions About Trends & Impacts of Biocontrol on Spotted Knapweed in MN u u No Pre-release data – no Knapweed density, stem counts, rosette counts, etc. before biocontrol. – no records of other vegetation present at beginning of invasion or before biocontrol. – In general, what was the site like before biocontrol? – Now we at least have baseline data to compare new data to in the future. High variability between the many unique sites – both in site characteristics and the agent combinations and numbers released; few trends could be identified across sites within any parameters. – indicates sites have to be treated on a site-by-site basis.
Other Observations & Lessons Learned u Visible decrease in knapweed. u Urophora flies – they’ve established everywhere and can distribute on their own. We no longer put efforts into moving them. u Sites with a combination of root agents and seedhead agents seemed to give better control.
Best Biocontrol Impacts Observed = Larinus spp. Urophora spp. + Cyphocleonus achates Agapeta zoegana
Other Benefits: u Minnesota Cooperative Weed Biological Control Project: MDA, USDA-APHIS, MN DNR, MN DOT, MN Association of County Ag. Inspectors, USFWS, University of Minnesota, Private Landowners. u Renewing and gaining new interest in the program, and regenerating communication and implementation between spotted knapweed biocontrol collaborators. u Collaborators were great source of impact feedback.
-Based on observations, we can now make biocontrol recommendations. -Data coming in later may modify these recommended practices. -Also started a 7 yr. IPM project with MN DOT using biocontrol and herbicide in 2006 – we’ll see!
For More Information Natasha Northrop, MDA Weed Biocontrol Program: natasha. [email protected] mn. us MDA Spotted Knapweed Biological Control Video: Using Advanced Technology for Efficient Fieldwork www. mda. state. mn. us/weedcontrol/knapweed. htm MDA Integrated Pest Management Program: www. mda. state. mn. us/weedcontrol MDA Weed Mapping System & Viewer www. mda. state. mn. us/weedcontrol/mapping. htm Legislative-Citizen’s Commission on MN Resources www. commissions. leg. state. mn. us/lcmr. htm