United States Department of Agriculture TECHNOLOGY TRANSFER Biological Control BIOLOGY AND BIOLOGICAL CONTROL OF KNAPWEEDS Rachel Winston, Mark Schwarzländer, Carol Bell Randall, and Richard Reardon Forest Health Technology FHTET-2011-05 Enterprise Team Reprinted August 2015 This publication reports research involving pesticides. It does not contain rec- ommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. CAUTION: Pesticides can be injurious to humans, domestic animals, de- sirable plants, and fish or other wildlife--if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides. Cover Photo: Michael Shephard he Forest Health Technology Enterprise Team (FHTET) was created in 1995 by the TDeputy Chief for State and Private Forestry, USDA, Forest Service, to develop and deliver technologies to protect and improve the health of American forests. This book was published by FHTET as part of the technology transfer series. http://www.fs.fed.us/foresthealth/technology/ The views and opinions expressed in this publication are those of the authors and do not neces- sarily reflect the official policy or positiion of any agency of the United States Government. 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Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program. [email protected]. USDA is an equal opportunity provider, employer, and lender. The use of trade, firm, or corporation names in this publication is for information only and does not constitute an endorsement by the U.S. Department of Agriculture. BIOLOGY AND BIOLOGICAL CONTROL OF KNAPWEEDS 2012 Revision by: Rachel Winston Carol Bell Randall Environmental Consultant Entomologist MIA Consulting, LLC USDA Forest Service Shelley, ID Forest Health Protection Coeur d’Alene, ID Mark Schwarzländer Richard Reardon Associate Professor USDA Forest Service Department of Plant, Soil, and 180 Canfield Street Entomological Sciences Morgantown, WV University of Idaho Moscow, ID Original Version By: Linda M. Wilson Carol Bell Randall Manager, Invasive Plant Entomologist Management Program USDA Forest Service British Columbia Ministry of Forest Health Protection Agriculture and Lands Coeur d’Alene, ID Abbotsford, BC For additional copies of this publication, contact: Richard Reardon Carol Bell Randall Mark Schwarzländer USDA Forest Service USDA Forest Service University of Idaho 180 Canfield Street 3815 Schreiber Way Moscow, ID 83844 Morgantown, WV 26505 Coeur d’Alene, ID 83815 (208) 885-9319 (304) 285-1566 (208) 765-7343 [email protected] [email protected] [email protected] Acknowledgments We would like to thank all of the county weed superintendents and land managers that we have worked with through the years for encouraging us to develop our series of biology and biological control manuals. We would also like to thank all of the excellent photographers who contributed many of the photographs in this manual. Some of the material in this manual was adapted from the manuals for the Biology and Biological Control of Leafy Spurge and Exotic Thistles. We wish to acknowledge the authors of the original material (Drs. Rich Hansen, Rodney Lym, Rob Bourchier, Andrew Norton, and Eric Coombs). Finally, we would like to thank Chuck Benedict, contractor for USDA Forest Service-Forest Health Technology Enterprise Team (FHTET), for help with editing, layout, and graphics; and Richard Reardon, FHTET, for producing this book. Biology and Biological Control of Knapweeds Table of contents Chapter 1: Introduction 1 Overview ................................................................................................................................................................ 1 Classical biological control of weeds ...................................................................................................................... 2 Code of best practices for classical biological control of weeds ............................................................................. 4 Biological control of knapweeds ............................................................................................................................ 4 Integrated weed management ............................................................................................................................... 5 Is biological control of knapweeds right for you? .................................................................................................. 5 About this manual .................................................................................................................................................. 6 Chapter 2: Getting to know knapweeds ......................................................................................... 9 Introduction ........................................................................................................................................................... 9 Knapweed development ........................................................................................................................................ 9 Simple key to six knapweed species commonly found in Wesern North America ..............................................12 Taxonomic classification of knapweeds ................................................................................................................ 13 Species descriptions of knapweeds ...................................................................................................................... 13 Spotted knapweed ...............................................................................................................................................................14 Diffuse knapweed ................................................................................................................................................................16 Squarrose knapweed ...........................................................................................................................................................18 Meadow knapweed .............................................................................................................................................................20 Black knapweed ...................................................................................................................................................................22 Brown knapweed .................................................................................................................................................................24 North American Centaurea ............................................................................................................................... 27 Related species ..................................................................................................................................................... 29 Chapter 3: Biology of knapweed biological control agents .......................................................... 31 History .................................................................................................................................................................. 31 Basic insect biology .............................................................................................................................................. 31 Beetles (Order Coleoptera) ...................................................................................................................................................32 Flies (Order Diptera) .............................................................................................................................................................33