Pesticide Residues in Hydroponic Lettuce Dr Sophie Parks NSW Department of Industry and Investment Project Number: VG07165 VG07165 This report is published by Horticulture Australia Ltd to pass on information concerning horticultural research and development undertaken for the vegetable industry. The research contained in this report was funded by Horticulture Australia Ltd with the financial support of the vegetables industry. All expressions of opinion are not to be regarded as expressing the opinion of Horticulture Australia Ltd or any authority of the Australian Government. The Company and the Australian Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests. This report was previously confidential. The confidentiality period has now expired. Please ignore all references to confidentiality within the report. ISBN 0 7341 2570 4 Published and distributed by: Horticulture Australia Ltd Level 7 179 Elizabeth Street Sydney NSW 2000 Telephone: (02) 8295 2300 Fax: (02) 8295 2399 © Copyright 2011 FINAL REPORT Review of pesticide residues in hydroponic lettuce HAL Project VG07165 Sophie Parks and Katina Lindhout Gosford Primary Industries Institute September 2008 1 HAL VG 07165 Project leader: Dr Sophie Parks, Plant Physiologist NSW Department of Primary Industries Gosford Primary Industries Institute Locked Bag 26, Gosford NSW, 2250 Key Personnel: Katina Lindhout, Joshua Jarvis, Carly Low Collaborators: Len Tesoriero, Peter Dal Santo, Graeme Smith The purpose of this project was to conduct a review of hydroponic systems and the practices associated with these in the production of hydroponic lettuce in Australia. This project was facilitated by Horticulture Australia Limited (HAL) in partnership with Ausveg and was funded by the vegetable levy. The Australian Government provides matched funding for all HAL’s research and development activities. Acknowledgements: The project team wish to thank those that assisted with this review. Editors of this report included Joseph Ekman, Leigh Pilkington, Virginia Brunton, David Hall and Alison Anderson. Those involved with the industry, who kindly provided information included Joseph Ekman, Sylvia Jelink, Tanya Shaw, Leanne Forsythe, Basem Al-khawaldeh, Jeremy Badgery-Parker, Michelle Smith, Sandra McDougall, Darren Waterson (NSW DPI), Tony Burfield (SARDI), Sloberdan Vujovic (Victoria DPI), Peter Dal Santo (AgAware Consulting), Alan Norden (APVMA), Graeme Smith (AHGA) and Brad Wells (HAL). Finally, we would like to thank the hydroponic lettuce growers who volunteered to be interviewed and provided detailed information on their production system and practices. Disclaimer: Any recommendations contained in this publication do not necessarily represent current NSW DPI and HAL policy. No person should act on the basis of the contents of this publication, whether as to matters of fact or opinion or other content, without first obtaining specific, independent professional advice in respect of the matters set out in this publication. 2 TABLE OF CONTENTS MEDIA SUMMARY ................................................................................................................ 4 TECHNICAL SUMMARY ...................................................................................................... 5 INTRODUCTION .................................................................................................................... 7 Potential impacts on pesticide residues in hydroponic lettuce ............................................. 8 1. Spray equipment ....................................................................................................... 8 2. Media (soil vs water) ................................................................................................ 8 3. Volatisation, photodegradation and wash-off ........................................................ 9 4. Lettuce types and varieties ...................................................................................... 9 5. Withholding periods and application rates ............................................................ 9 6. Farm and crop management ................................................................................... 9 7. Season ...................................................................................................................... 10 8. Pesticide properties ................................................................................................ 10 9. Plant properties ...................................................................................................... 10 AIMS AND OBJECTIVES OF THE STUDY ..................................................................... 10 SURVEY .................................................................................................................................. 11 SURVEY METHODOLOGY ................................................................................................ 11 RESULTS OF THE SURVEY .............................................................................................. 11 Summary of grower interviews ............................................................................................ 11 Overview of hydroponic lettuce production systems and management ............................. 13 1. Industry profile ....................................................................................................... 13 2. Production systems ................................................................................................. 14 3. Water and nutrient solution management ........................................................... 14 4. General system maintenance ................................................................................. 16 5. Lettuce types and varieties .................................................................................... 16 6. Stock management .................................................................................................. 16 7. Pest and disease management ................................................................................ 17 8. Spray equipment ..................................................................................................... 18 9. Crop hygiene ........................................................................................................... 19 10. Postharvest practices .......................................................................................... 19 11. Pesticide use ........................................................................................................ 19 Key components of hydroponic lettuce systems and crop management ............................ 22 RECOMMENDATIONS ....................................................................................................... 26 1. Determine the movement of pesticides in hydroponic lettuce production ................. 26 2. Provide access to a range of pesticides ....................................................................... 26 3. Develop pesticide alternatives...................................................................................... 27 4. Reduce pest and disease pressure ............................................................................... 27 APPENDIX 1 .......................................................................................................................... 29 Article in Lettuce Leaf ................................................................................................... 29 Survey questions used to detail responses from interviews with growers ................. 29 APPENDIX 2 .......................................................................................................................... 31 Spraysense fact sheet ...................................................................................................... 31 APPENDIX 3 .......................................................................................................................... 34 Currently available extension resources....................................................................... 34 APPENDIX 4 .......................................................................................................................... 36 An introduction to hydroponics .................................................................................... 36 3 MEDIA SUMMARY In response to consumer preferences for clean produce, market specifications for hydroponic lettuce describe a product that is free from pests, pest damage and disease symptoms. Growers are able to use pesticides to reduce pests and diseases but for hydroponic lettuce in particular pesticide residues have been found to exceed the maximum residue limit (MRL) more frequently than for other targeted products. The reasons for this are not fully understood. In order to evaluate how hydroponic systems and associated practices might affect residues in lettuce, a current description of these systems and crop management practices is needed. Information for this purpose was gathered from literature (industry and scientific reports) and from interviews with growers and others associated with the industry. Hydroponic lettuce production systems differ in comparison to other hydroponic production systems used in protected cropping. Most hydroponic lettuce systems are placed outdoors