The insect fauna of Canada thistle, Cirsium arvense (L.) Scop. in southern Montana by Hilde De Smet-Moens A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Biological Sciences Montana State University © Copyright by Hilde De Smet-Moens (1982) Abstract: Insects associated with Cirsium arvense (L.) Scop, in southern Montana are reported. Fifty-six phytophagous species and 47 visiting insects were collected, identified and tabulated. Four insect species, Corythucha distincta Osborn and Drake (Hemiptera: Tingidae), Bans sp., poss. cirsii Gilbert (Coleoptera: Curculionidae), Vanessa cardui L. (Lepidoptera: Nymphalidae), and Orellia ruficauda (Fabricius)(Diptera: Tephritidae), were considered conspicuous, because of their damage inflicted to the thistle plant. More insects were found associated with the developing seed heads than with foliage, stems or roots. The information gathered on this local survey can be valuable for future introductions of insect biological control agents. It forms the foundation for follow-up studies with indigenous insect species. Augmentation and redistribution of established monophagous insects, such as Ceuthorynchus litura and Baris sp. should be considered. Transmission experiments are necessary to evaluate the potential of these monophagous insects as thistle pathogen vectors. The combination of two stress-factors will increase the impact on the thistle plant in the field. STATEMENT OF PERMISSION TO COPY In presenting this thesis in partial fulfillment of the require­ ments for an advanced degree at Montana State University, I agree that the Library shall make it freely available for inspection. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by my major professor, or, in his absence, by the Director of Libraries. It is understood that any copying or publi­ cation of this thesis for financial gain shall not be allowed without my written permission. SignatuIe Date THE INSECT FAUNA OF CANADA THISTLE, CIRSIUM ARVENSE (L.) SCOP IN SOUTHERN MONTANA by . HILDE DE SMET-MOENS A thesis submitted in partial fulfillment of the requirements for the degree of ' MASTER OF SCIENCE in Biological Sciences Approved: MONTANA STATE UNIVERSITY Bozeman, Montana August, 1982 / / iii . ACKNOWLEDGMENTS I wish to acknowledge and express my appreciation for the contri­ butions of the following people: Dr. W. L. Morrill, my major professor, for his professional assist­ ance throughout this research project; The members of my thesis committee. Dr. P. K. Fay, Dr. S. R. Eversman, and Mr. J. M. Story, for their time and invaluable advice; Mrs. S. D. Rose, Curator of the M.S.U. Entomological Collection, for her taxonomic advice and help; All the systematicists who identified the insects mentioned in this report: the taxonomists.of the Systematic Entomology Laboratory, USDA, Beltsvil.le, MD; and the National Museum of Natural History, Smithsonian Institution, Washington, DC; J. Lattin, P. Oman, K. A. Phillips, and G. M. Stonedahl, Oregon State University, Corvallis; L. A. Kelton, Bio- systematics Research Institute, Ottawa; M. W. Nielson, Forage Insects Research Laboratory, Tucson, AZ; G. J. Michels, Jr., Texas A&M Univer­ sity, Amarillo; R. J. Beshear, The University of Georgia, Experiment; J. A. Onsager and E. A. Oma, U.S.D.A. Rangeland Insect Laboratory, Bozeman; R. M. Bohart, University of California, Davis; D. K. Young, Michigan State University, East Lansing; . The Western Agricultural Research Center and the Montana weed d istricts for the funding of this research project. TABLE OF CONTENTS Page VITA .................................................... i.i ACKNOWLEDGMENTS ...................... iii LIST OF TABLES..................................................................... v LIST OF FIGURES . .............................................................................. vi ABSTRACT ................................................................. vii INTRODUCTION.................................................... I LITERATURE REVIEW .................... ........ 3 CO (T i The Host Plant ............................................ ..................... Biological Control of Canada Thistle .................. Biological Control of Canada Thistle in Montana MATERIALS AND METHODS . , ......................-. ........................... 12 Study S i t e s ..................................................................................................... 12 Collecting M ethods........................................... 12 Experimental R earings................................................ .... ' .................. 15 Field Studies..................... 16 Insect Identification.................. 16 RESULTS AND DISCUSSION.................................. 18 Phytophagous Insects .............................................. 18 Visitors, Predators and Parasitoids............ 38 Summary...................... .....................................................■ 42 LITERATURE CITED .......................................................................... 46 V LIST OF TABLES Table Page 1. Information on the insects released in Montana for the biological control of Canada thistle ............................... 10 2. Selected collection sites of the 1981 insect survey on Canada t h i s t l...................... e .......................................... 14 3. Phytophagous insects collected from Canada th istle , Cirsium aryense (L.) Scop., in southern Montana, 1981 . ............................................................ 19 4. Average plant heights of eight Baris infested and eight uninfested thistle plants in sites 5 and 6, June 19, 1981. .............................. ................................... 30 5. Infestation of Canada thistle heads by Orellia ruficauda (Fabricius), September 3, 1981 . ............................ 37 6. Visitors, predators, and parasitoids collected from Canada th istle , Cirsium arvense (L.) Scop. in southern Montana, 1981 .T..................... .......................................... 39 7. Parasitism of Orellia ruficauda (Fabricius) pupae in Canada th istle seed heads, September^, 1981 . 43 vi LIST OF FIGURES Figure Page 1. Collection sites of the insect survey on Canada thistle, 1981............................................................................... 13 2. Emergence trap in site 5 . ......................................................... 17 3. Corythucha distincta adults feeding on Canada th istle leaves . ................................................................. 23 4. Feeding damage of Corythucha distincta on Canada th istle . ............................................... 23 5 . • Aggregation of Corythucha distincta nymphs on the under-side of Canada th istle leaves........ 25 6. Baris sp. adult feeding on th istle rosette............................... 28 7. Feeding damage of Baris sp. adults on potted thistle plants in the insectary .......................... 31 8. Baris sp. larva in Canada th istle r o o...................... t 31 9. Wilted th istle plant in site 5, infested with Baris sp. l a r v a e .......................................................................... 31 10. Linear regression of plant height versus larval frequency, August 19 8 1 ........................................................ 33 11. Feeding damage of Orellia ruficauda. larvae on Canada th istle seeds. .................................... - ............................. 36 .12. Parasitized Orellia ruficauda pupa . .................................... 44 .ABSTRACT Insects associated with Cirsium arvense (I.) Scop, in southern Montana are reported. Fifty-six phytophagous species, and 47.visiting insects were collected, identified and tabulated. Four insect species, Corythucha distincta Osborn and Drake (Hemiptera: Tingidae), Bans sp., poss. cirsii Gilbert (Coleoptera: Curculionidae), Vanessa^cardui L. (Lepidoptera: Nyrnphalidae),. and Orellia ruficauda (Fabricius)(Diptera: Tephritidae), were considered, conspicuous, because of their damage inflicted to the th istle plant. More insects were found associated with the-developing seed heads than with foliage, stems or roots. The information gathered oh.this local survey can be valuable for future introductions of insect, biological control agents. It forms the foundation for follow-up studies with indigenous insect species. Augmentation and redistribution of established monophagous insects such as Ceuthorynchus litura and Baris sp. should, be considered. Trans mission experiments are necessary to evaluate the potential of these' monophagous insects, as th istle pathogen vectors. The combination of . two stress-factors will increase the impact on the thistle plant in . the field. - INTRODUCTION Cultural and chemical control practices have historically been the main approaches to weed control. Both methods are aimed at removing unwanted plants as quickly as possible, a short term approach requiring considerable annual expenditures of resources and energy (Andres and Gpeden, 1971). Biological control of weeds has become a popular alterna­ tive because it is a means of controlling weeds without the high energy costs of cultural practices and without the residue and pollution prob­ lems of herbicides. Biological control of weeds is the deliberate use of insects or other plant parasites to reduce the density of a weed to an acceptable level (Harris, 1971b). Biocontrol, when effective, is relatively inex­ pensive, long-lasting