Biological control of Canada thistle: Host range of Hadroplontus litura on native Cirsium spp. Elizabeth Katovich • Roger Becker • Mary Marek-Spartz • Monika Chandler • Laura Van Riper Acknowledgements Research assistants Kylie Rich • Ryan Mentz • Aryane Batista • Lewis Scheaffer • Hugo Dos Santos Oliveira Seed Sources Laura Van Riper • Ross Hier (Minnesota Dept. of Natural Resources) Welby Smith • Dan Wovcha (Minnesota Biological Survey, MNDNR) Matt Graeve (The Nature Conservancy) Karyri Havens (Chicago Botanic Garden) Kay Kottas (Prairie Legacy Inc.) Photos Peter M. Dziuk Roger Becker Jeanie Katovich Bugwood Image Database System: https://images.bugwood.org Cirsium arvense a.k.a. Canada or creeping thistle Perennial plant that spreads rapidly via seed dispersal and lateral roots Prohibited noxious weed in Minnesota (listed in 43 states) One of the most common weeds in pastures, roadsides, and prairies Costs millions of dollars annually in direct crop loss and management efforts The aggressive invasion of upland, wetland, and dune habitats by C. arvense threatens the biodiversity of other flowering plants and native thistles, which provide ecological services to pollinators and seed-feeding birds. Hadroplontus litura Family: Curculionidae Tribe: Ceutorhynchini Released in Canada in 1965 from France/Germany/Switzerland Introduced to U.S. in 1972 Established in Idaho, Montana, Colorado, Nebraska, North Dakota, Oregon, Utah, Virginia, Washington, and Wyoming Introduced to a limited area in MN in late 90's and the naughts http://www.grandforksherald.com/sports/outdoors/2177237-agassiz-national-wildlife-re fuge-celebrates-75th-anniversary H. litura released in fall 2007 and spring 2008 at Lake Agassiz NWR Monika Chandler, MDA 9/15/09 10/03/12 Objective Determine the host range of H. litura on MN native Cirsium thistles before implementing a broader release of the biocontrol agent in the state. efficacy generalist specific efficacy generalist specific Initial host range testing of H. litura Attacks species in the Cirsium-Silybum-Carduus complex of the Asteraceae subtribe Carduinae (Zwolfer and Harris 1966; Canadian J. of Zoology 44:23-38) Policy was focused on plants of agricultural significance. Not all native Cirsium were tested. No native Carduus or Silybum in N.A., but 118 Cirsium spp. (Barkley, Brouillet, & Strother 2006) We selected seven Cirsium thistles based on their presence in or proximity to Minnesota. Native Cirsium spp. Tall thistle Field thistle Flodman's thistle Hill's thistle Wavy leaf thistle Pitcher's thistle Swamp thistle Biennial thistles Field thistle Tall thistle Swamp thistle Cirsium discolor Cirsium altissimum Cirsium muticum Perennial thistles Flodman's thistle Cirsium flodmanii Common throughout the Northern great plains, Rocky Mountains and Canada Wavyleaf thistle Cirsium undulatum Native to IA, ND, SD, WI Hill's thistle Ordway Prairie Cirsium hillii NCS Glenwood, MN Species of Special Concern Native to Minnesota prairies Biennial Pitcher's thistle Cirsium pitcheri Threatened species Native to sandy shorelines of upper great lakes Perennial Biology of H. litura (in cooler climates) March April May June July August September Winter Adults appear early spring. Larvae complete 3 instars in Overwinter as Mating and oviposition begins plant, mining the stem, pupate adults to with emergence of thistle in the soil. F1 generation emerge and shoots (March - mid-May) emerges late summer mate/lay eggs for.gov.bc.ca the following spring Philipp Wickey, Philipp Wickey, inaturalist.org inaturalist.org Preparing for host range tests Seeds of native thistles collected and stratified for ~16 weeks, then planted in spring. Seedlings were transplanted to 3 gallon pots in the fall for overwintering. H. litura purchased from Biological Control of Weeds Inc. in Bozeman, MT Put on potted and caged Canada thistle plants in late summer. Overwintered on University of Minnesota St. Paul campus Sequential no-choice oviposition tests Hadroplontus litura Sequential No-Choice Oviposition Tests with Cirsium species. St. Paul, MN 2016. Mean no. Species Scientific name Number of Mean percent Total number eggs per ± Mean SE replications feeding of eggs replication Canada thistle Cirsium arvense 74 2.2 309 4.2 0.4 field thistle Cirsium discolor 10 2.4 77 7.7 1.3 Flodman's thistle Cirsium flodmanii 10 2.2 56 5.6 0.9 Pitcher's thistle Cirsium pitcheri 10 0.8 41 4.1 1.0 swamp thistle Cirsium muticum 10 1.1 89 8.9 1.4 tall thistle Cirsium altissimum 10 3.0 106 10.6 1.9 wavyleaf thistle Cirsium undulatum 10 1.0 45 4.5 1.0 Hadroplontus litura Sequential No-Choice Oviposition Tests with Cirsium species. St. Paul, MN 2016. Mean no. Species Scientific name Number of Mean percent Total number eggs per ± Mean SE replications feeding of eggs replication Canada thistle Cirsium arvense 74 2.2 309 4.2 0.4 field thistle Cirsium discolor 10 2.4 77 7.7 1.3 Flodman's thistle Cirsium flodmanii 10 2.2 56 5.6 0.9 Pitcher's thistle Cirsium pitcheri 10 0.8 41 4.1 1.0 swamp thistle Cirsium muticum 10 1.1 89 8.9 1.4 tall thistle Cirsium altissimum 10 3.0 106 10.6 1.9 wavyleaf thistle Cirsium undulatum 10 1.0 45 4.5 1.0 Single-choice oviposition test Single-choice oviposition tests with Hadroplotus litura on Cirsium species. St. Paul, MN 2017-2018. No. of Mean egg number per plant Percent eggs on Species Scientific name replications Native thistle Canada thistle Native thistle Canada thistle field thistle Cirsium discolor 6 4.8 2.5 66 34 Flodman's thistle Cirsium flodmanii 7 2.4 2.9 46 54 Hill's thistle Cirsium pumilum var. 5 0.6 3.2 16 84 hillii Pitcher's thistle Cirsium pitcheri 7 1.1 4.1 22 78 swamp thistle Cirsium muticum 5 1.0 2.6 28 72 tall thistle Cirsium altissimum 6 1.5 4.8 24 76 Single-choice oviposition tests with Hadroplotus litura on Cirsium species. St. Paul, MN 2017-2018. No. of Mean egg number per plant Percent eggs on Species Scientific name replications Native thistle Canada thistle Native thistle Canada thistle field thistle Cirsium discolor 6 4.8 2.5 66 34 Flodman's thistle Cirsium flodmanii 7 2.4 2.9 46 54 Hill's thistle Cirsium pumilum var. 5 0.6 3.2 16 84 hillii Pitcher's thistle Cirsium pitcheri 7 1.1 4.1 22 78 swamp thistle Cirsium muticum 5 1.0 2.6 28 72 tall thistle Cirsium altissimum 6 1.5 4.8 24 76 No-choice larval development tests Marked ovipositing adults 2 weeks ~6 weeks remove weevils check for larval tunneling and newly emerged No-choice larval development test Number of Species Scientific name Number of replications Numbers of adults emerged replications with mining With adult Mean per Range per Total Total emergence1 replication replication Canada thistle Cirsium arvense 10 8 27 2.7 0 to 7 8 field thistle Cirsium discolor 8 6 112 14.0 0 to 43 7 Flodman's thistle Cirsium flodmanii 5 1 9 1.8 0 to 9 4 Pitcher's thistle Cirsium pitcheri 5 0 0 0.0 0 1 Hill's thistle* Cirsium pumilum var. 5 0 0 0.0 0 0 hillii swamp thistle Cirsium muticum 7 5 7 1.0 0 to 2 5 tall thistle Cirsium altissimum 5 2 6 1.2 0 to 5 3 1Sum of alive and dead adults No-choice larval development test Number of Species Scientific name Number of replications Numbers of adults emerged replications with mining With adult Mean per Range per Total Total emergence1 replication replication Canada thistle Cirsium arvense 10 8 27 2.7 0 to 7 8 field thistle Cirsium discolor 8 6 112 14.0 0 to 43 7 Flodman's thistle Cirsium flodmanii 5 1 9 1.8 0 to 9 4 Pitcher's thistle Cirsium pitcheri 5 0 0 0.0 0 1 Hill's thistle Cirsium pumilum var. 5 2 0 0 0.0 0 0 hillii swamp thistle Cirsium muticum 7 5 7 1.0 0 to 2 5 tall thistle Cirsium altissimum 5 2 6 1.2 0 to 5 3 1Sum of alive and dead adults Cirsium Hillii no-choice larval development tests H. litura* larval tunneling in three Cirsium species efficacy generalist specific Conclusions... Does not distinguish C. arvense from native efficacy MN Cirsium spp. generalist specific Mixed results on H. litura efficacy Establishment of H. litura at four sites in Montana resulted in higher winter mortality rates of underground roots 15 years after release. (Rees, 1990; Weed Sci. 38:198-200) H. litura did not reduce thistle stem counts, flowering, or overwinter survival in C. arvense stands on two South Dakota wildlife refuges over four years. (Reed et al., 2006; Nat. Areas J. 26:47-52) Significant decline in Canada thistle abundance after ten years when H. litura was released in combination with the gall forming fly, Urophora cardui, and the seed-head weevil, Larinus planus. (Markin and Larson 2011; XIII International Symp. on Biol. Control of Weeds) No significant reduction in stem density of C. arvense in Idaho after release of H. litura and U. cardui (Price et al. 2018; XV International Symp. on Biol. Control of Weeds) Conclusions... May not be successful (or at least highly variable) in control of C. arvense populations Does not distinguish C. arvense from native MN Cirsium spp. efficacy generalist specific Documenting negative results contribute to the search for a safe biocontrol agent for C. arvense and inform responsible weed biocontrol practices The .