ii ACKNOWLEDGMENTS I sincerely thank Michael Draney, Mathew Dornbush and Rachel Russell for their guidance in this project. I would also like to thank Matthew Oehmichen for assistance in field sampling, Monika Chandler of Minnesota Department of Agriculture with sampling materials, Clarissa Hammond of Wisconsin Department of Agriculture, and the Wildlife staff at the Wisconsin Department of Natural Resources for GIS data. iii ABSTRACT RATE OF DISPERSAL OF SPOTTED KNAPWEED BIOCONTROL BEETLES (LARINUS SPP.: CURCULIONIDAE) IN WISCONSIN (Wade Oehmichen) Eurasian seed-head weevils, Larinus obtusus Gyllenhal and Larinus minutus Gyllenhal (Coleoptera: Curculionidae), were released annually from 2004-2013 across Wisconsin for biological control of the invasive forb spotted knapweed (Centaurea stoebe L. ssp. micranthos (Gugler) Hayek). In 2014, Larinus spp. presence/absence surveys were conducted at 18 previous releases sites between 7/18/2014 – 8/16/2014 from 2007 (n=3), 2008 (n=3), 2009 (n=3), 2010 (n=6), 2011 (n=1) and 2012 (n=2). We did not detect any Larinus spp. at two of the sites (2011 and 2012) both in Door County and on four of the sites (2 - 2007, 2 - 2010) positive locations of Larinus spp. exceeded the maximum extent of survey, the point past where other previous releases of Larinus spp. were then closer to any Larinus spp. potentially detected. We found a significant, linear relationship between time since release and the natural log of the observed dispersal rates of Larinus spp. (F1,10 = 18.8, P = 0.002, R2 = 0.65), suggesting an increasing dispersal rate through time. Modeled result suggested the following relationship: LN(Dispersal distance in km) = 0.258*time since release + 0.741. Because the model intercept (i.e. dispersal rate) did not pass through zero at age zero, which was expected from a biological basis, I warn against extrapolating the modeled dispersal rate to the period from release (t=0) to the end of Year One. Applying these dispersal rates to all 326 previous Larinus spp. releases in Wisconsin we predict that by 2017 low level populations of Larinus spp could be found state-wide. This would add to the two other spotted knapweed biological control agents, Urophora affinis Frauenfeld and U. quadrifasicata (Meigen) (Diptera: Tephritidae) that are already well distributed throughout Wisconsin. My study suggests that with Larinus spp. also ubiquitous across Wisconsin future resources should focus on increasing the distribution of the less well distributed spotted knapweed biological control agents, Cyphocleonus achates (Fahraeus) (Coleoptera: Curculionidae) and Agapeta zoegana (Lepidoptera: Cochylidae). iv TABLE OF CONTENTS ACKNOWLEDGEMENTS ..................................................................................................... ii ABSTRACT ............................................................................................................................. iii TABLE OF CONTENTS ........................................................................................................ iv LIST OF TABLES .................................................................................................................. vi LIST OF FIGURES ............................................................................................................... vii 1. LITERATURE REVIEW .....................................................................................................1 1.1 Biology of spotted knapweed ..................................................................................3 1.2 Damage of spotted knapweed .................................................................................5 1.3 Control of spotted knapweed ..................................................................................5 1.4 Biological control of spotted knapweed .................................................................8 1.5 Dispersal of Larinus spp .......................................................................................24 2. INTRODUCTION ..............................................................................................................26 3. METHODS .........................................................................................................................29 3.1 Study sites .............................................................................................................29 3.2 Sampling protocol .................................................................................................30 3.3 Data analysis summary .........................................................................................33 4. RESULTS ...........................................................................................................................34 v 5. DISCUSSION .....................................................................................................................37 5.1 Dispersal ...............................................................................................................37 5.2 Policy Recommendations ......................................................................................40 REFERENCES .......................................................................................................................44 APPENDIX A: EXAMPLE OF DIRECTIONAL SURVEY WINDOW BUFFER .....................................................................................................................50 vi LIST OF TABLES Table 1. History of the first releases of spotted knapweed biological control agents ...............9 Table 2. The summary of the 113 field presence/absence survey samples of Larinus spp. (Sept – Oct, 2014). .....................................................................................................32 Table 3. The annual dispersal rate of Larinus spp. of the 12 sites, where positive Larinus spp. were found and maximum survey extent was not reached .........................................35 vii LIST OF FIGURES Figure 1. The reported presence of spotted knapweed on WDNR properties ...........................1 Figure 2. Potential area of infestation of spotted knapweed in Wisconsin. ...............................2 Figure 3. Spotted knapweed herbicide treatment site at Buena Vista Wildlife Area in Wisconsin Rapids, WI ..................................................................................................7 Figure 4. Urophora affinis photos of adult, gall and larva .....................................................10 Figure 5. Urophora quadrifasciata photos of adult, gall and larva ........................................11 Figure 6. Agapeta zoegana photos of adult and larvae ...........................................................13 Figure 7. Cyphocleonus achates photos of adult and larva. ....................................................14 Figure 8. Photo of adult Bangasternus fausti...........................................................................15 Figure 9. Identifying characteristics of adult Larinus minutus Hochhuth. .............................16 Figure 10. Development of Larinus spp. within spotted knapweed seedhead. ......................17 Figure 11. Identifying characteristics of adult Larinus obtusus Gyllenhal. ............................18 Figure 12. Wisconsin releases of Cyphocleonus achates between 2004 – 2014. ...................21 Figure 13. Wisconsin releases of Agapeta zoegana between 1991 – 2014. ..........................22 Figure 14. Agapeta zoegana cocoon extracted from spotted knapweed root and potting soil. .............................................................................................................................23 Figure 15. The 326 previous Larinus spp. field releases (2002 – 2014) ................................29 Figure 16. Pupal chambers left in heads of spotted knapweed by Larinus spp. .....................31 Figure 17. The dispersal rate of Larinus spp. by years since released, based on data collected in 2014 .........................................................................................................................36 viii Figure 18. The potential distribution of Larinus spp. in Wisconsin based on calculated dispersal rate applied to all 326 Larinus spp. releases with spotted knapweed potential distribution. .................................................................................................................41 Figure 19. The potential distribution of Larinus spp. in Wisconsin in year 2017 ..................42 Figure 20. Larinus spp. survey window for site 15 with multiple buffer ring (0.8 km increment) ....................................................................................................................51 1 1. LITERATURE REVIEW Spotted knapweed (Centaurea stoebe L. spp. micranthos (Guler) Hay/synonym C. biebersteinii L. formerly C. maculosa Lam.) is native to southeastern Europe and was first reported in North America in 1893 (Groh 1944) as a contaminant in alfalfa seed in British Columbia (Roche and Talbot 1986). It spread from British Columbia to Wisconsin by the early 1900’s (Fassett 1927). It is estimated that spotted knapweed currently infests around 6.9 million acres in the U.S. (Duncan 2005). In an unpublished internal survey done by the Wisconsin Department of Natural Resources (WDNR) (2009) a list of managed properties throughout Wisconsin was sent to the corresponding land managers on whether or not known spotted knapweed populations existed on those properties (Fig 1). Figure