How Herbicides Work Biology to Application Linda Hall Agriculture Research Division Alberta Agriculture and Rural Development Hugh Beckie Thomas M. Wolf Saskatoon Research Centre Saskatoon Research Centre Agriculture and Agri-Food Canada Agriculture and Agri-Food Canada Disclaimer While every effort has been made to ensure accuracy, Alberta Agriculture and Rural Development does not accept responsibility for errors or ommissions. It remains the responsibility of the readers to follow product information contained on the product label or package insert. The publisher, editor and all contributors to this publication cannot be held responsible for publication errors or any consequence resulting from the use of this publication. Published by: Alberta Agriculture and Rural Development Information Management 7000 - 113 Street Edmonton, Alberta Canada T6H 5T6 Editors: Chris Kaulbars and Gerard Vaillancourt Graphic Designer: John Gillmore Electronic Composition: Sherrill Strauss and J.A. Serafinchon Photographs: Beth Hoar – Alberta Agriculture and Rural Development David Wall – Agriculture and Agri-Food Canada Tom Wolf – Agriculture and Agri-Food Canada Dow AgroSciences Copyright © 1999. All rights reserved by Her Majesty the Queen in the right of Alberta. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical photocopying, recording, or otherwise without written permission from Information Management, Alberta Agriculture and Rural Development. Tables/chemical registrations updated 2009 to reflect current products. Original printing April 1999 Reprinted February 2014 ISBN 0-7732-6131-1 Contents Acknowledgments ........................................................................................................................ vii Foreword ........................................................................................................................................ viii How Herbicides Work ..................................................................................................1 Target sites .....................................................................................................................................1 Why herbicides kill plants ............................................................................................................5 Physical/chemical properties .......................................................................................................6 Uptake ............................................................................................................................................7 Translocation ..................................................................................................................................9 Selectivity and metabolism ........................................................................................................10 Toxicity..........................................................................................................................................12 Soil-Applied Herbicides ...........................................................................................13 Inhibitors of Cell Division ...........................................................................................................14 Physical/chemical properties .....................................................................................................15 Inhibition of cell division and cell enlargement .......................................................................16 Uptake and translocation ...........................................................................................................18 Metabolism and selectivity .........................................................................................................18 Symptoms .....................................................................................................................................20 Toxicity..........................................................................................................................................20 Implications for application .......................................................................................................20 Inhibitors of Very Long Chain Fatty Acid Biosynthesis ......................................................21 Physical/chemical properties .....................................................................................................21 Inhibition of very long chain fatty acids ...................................................................................22 Uptake and translocation ...........................................................................................................22 Metabolism and selectivity .........................................................................................................23 Toxicity..........................................................................................................................................23 Symptoms .....................................................................................................................................23 Implications for application .......................................................................................................23 i Amino Acid Biosynthesis Inhibitors .........................................................25 Inhibitors of Acetolactate Synthase (ALS/AHAS) ................................................................26 Physical/chemical properties .....................................................................................................27 Inhibition of acetolactate synthase (ALS/AHAS) ...................................................................27 Uptake and translocation ...........................................................................................................28 Metabolism and selectivity .........................................................................................................29 Toxicity..........................................................................................................................................29 Symptoms .....................................................................................................................................29 Implications for application .......................................................................................................30 Inhibitor of EPSPS .......................................................................................................................30 Physical/chemical properties .....................................................................................................31 Inhibition of EPSPS ...................................................................................................................32 Uptake and translocation ...........................................................................................................32 Metabolism and selectivity .........................................................................................................33 Symptoms .....................................................................................................................................33 Toxicity..........................................................................................................................................34 Implications for application .......................................................................................................34 Inhibitors of Glutamine Synthetase .........................................................................................35 Physical/chemical properties .....................................................................................................35 Inhibition of glutamine synthetase ...........................................................................................35 Uptake and translocation ...........................................................................................................36 Metabolism and selectivity .........................................................................................................36 Toxicity..........................................................................................................................................36 Symptoms .....................................................................................................................................37 Implications for application .......................................................................................................37 Inhibitors of ACCase ..................................................................................................39 ACCase Inhibitors .........................................................................................................................39 Physical/chemical properties .....................................................................................................40 Inhibition of ACCase ..................................................................................................................40 Uptake and translocation ...........................................................................................................42 Metabolism and selectivity .........................................................................................................42 Toxicity..........................................................................................................................................43