EXPOSURE AND RISK TO NON-TARGET RECEPTORS FOR AGRICULTURAL SPRAY DRIFT OF FORMULATION TYPES AND ADJUVANTS by Collin James Preftakes A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Ecology and Environmental Sciences MONTANA STATE UNIVERSITY Bozeman, Montana July 2017 ©COPYRIGHT by Collin James Preftakes 2017 All Rights Reserved ii DEDICATION To my grandfather, Dr. Marcel J. Kniedler (Nonno). iii ACKNOWLEDGEMENTS I would like to begin by thanking my advisor, Dr. Robert Peterson for his mentorship, guidance, and friendship that have been invaluable throughout this process. I am also extremely grateful to the other members of my committee, Dr. Jerome Schleier III, Dr. David Weaver, and Dr. John Martin for their expertise and insightful questions along the way. My parents, Nadine and James Preftakes, and my siblings, Justin, Katie, Heidi, Meggie, and Cori have shared in this experience as much as anyone. Their support and encouragement has been my greatest asset throughout this degree and throughout my life. My fiancé, Dayane Reis, has been especially instrumental in keeping me grounded and I am incredibly fortunate to have had her companionship in this pursuit. I am also very fortunate to have shared my experience as a graduate student with Dr. Chris Brown, Alyssa Piccolomini, Clair Donahoo, and Shavonn Whiten who were so much more than lab-mates. Thanks to João Rossi for graciously helping me with statistics during multiple weekends, and to my incredible group of friends for whom I would be lost without. My sincere thanks to the staff at the DAS Western U.S. Research Center where my experimental field work took place. That work would not have been possible without the help of Dr. Byron Sleugh, Dr. Joe Armstrong, Dr. Claudia Kuniyoshi, Dr. Cristiane Müller, Noemi Thompson, Marc Muzio, Garrick Stuhr, and all the summer interns. A special thanks to Dr. Scott Hutchins and Dr. Monica Sorribas for advocating on my behalf at Dow AgroSciences, from which financial support was generously provided. iv TABLE OF CONTENTS 1. LITERATURE REVIEW ................................................................................................1 Pesticides and Drift ..........................................................................................................1 Droplet Size as a Predictor of Spray Drift .......................................................................2 Causes of Drift .................................................................................................................4 Operator-Controlled Variables Affecting Drift ...............................................................4 Formulation and Adjuvant .......................................................................................4 Nozzle Type and Spray Pressure .............................................................................8 Driving Speed and Boom Height .............................................................................9 Non-Operator-Controlled Variables Affecting Drift .......................................................9 Wind Speed and Atmospheric Stability .................................................................10 Evaporation of Airborne Droplets .........................................................................11 Measuring and Predicting Drift .....................................................................................12 Ecotoxicology and Environmental Risk Assessment for Pesticide Drift ......................15 Research Objectives ......................................................................................................18 References .....................................................................................................................20 2. EFFECT OF INSECTICIDE FORMULATION AND ADJUVANT COMBINATION ON AGRICULTURAL SPRAY DRIFT ....................26 Contribution of Authors and Co-authors .......................................................................26 Manuscript Information Page ........................................................................................27 Abstract .........................................................................................................................28 Introduction ...................................................................................................................29 Methods .........................................................................................................................32 Results ...........................................................................................................................42 Ground Deposition .................................................................................................42 Vertical Deposition ................................................................................................46 Biological Efficacy ................................................................................................48 Discussion .....................................................................................................................49 Acknowledgments .........................................................................................................53 References .....................................................................................................................71 3. NON-TARGET INSECT RISK ASSESSMENT OF DRIFT REDUCTION INSECTICIDE FORMULATIONS AND SPRAY ADJUVANTS ...............................75 Contribution of Authors and Co-authors ........................................................................75 Manuscript Information Page .........................................................................................76 Abstract ...........................................................................................................................77 v TABLE OF CONTENTS CONTINUED Introduction .....................................................................................................................78 Methods...........................................................................................................................81 Results and Discussion ...................................................................................................86 Acknowledgments...........................................................................................................93 References .....................................................................................................................101 4. CONCLUSION ............................................................................................................104 CUMULATIVE REFERENCES .....................................................................................108 vi LIST OF TABLES Table Page 2.1. Sample areas for in-swath and downwind ground deposition samplers. ...........................................................................54 2.2 Application rates of Rhodamine-WT (RWT) for each treatment ............................................................................................55 2.3 Summary statistics for numerical variables .....................................................56 2.4 Coefficient estimates and SEs for selected ground deposition model ..............................................................................................57 2.5 Slope coefficients for interaction terms in regression models for ground deposition and volume median diameter ...........................58 2.6 Coefficient estimates and SEs for selected VMD model .................................59 2.7 Slope coefficients for interaction terms in regression models for ground deposition and volume median diameter ...........................60 2.8 Droplet size data from wind tunnel test with treatments ordered by ground deposition from the field study ..........................................61 S2.1 Recovery Rate of Rhodamine-WT for drift study .........................................67 S2.2 Mean Rhodamine-WT deposition on swath plates represented as a percentage of amount applied ..............................................68 S2.3 Ground deposition with increasing distance from the field edge as a percentage of Rhodamine-WT or a.i. applied ........................69 S2.4 Ground deposition of active ingredient with increasing distance from the field edge. .........................................................70 3.1 Acute sensitivity of terrestrial insects to spinosad from published ingestion bioassays. ................................................................94 vii LIST OF FIGURES Figure Page 2.1 Field layout for drift experiment in Fresno, CA ..............................................62 2.2 Predicted ground deposition of Rhodamine-WT as a function of distance at average RH and wind speed ........................................63 2.3. Predicted ground deposition of Rhodamine-WT as a function of wind speed at average RH and a distance of 1 meter ....................64 2.4 Droplet size by height ......................................................................................65 2.5 Interaction between VMD and Wind speed .....................................................66 3.1 Species sensitivity distribution of acute mortality (LC50) for terrestrial insect species exposed to spinosad through ingestion ...............97 3.2 Residue by distance data superimposed on SSD to show PAF for treatments at 5 m in a short grass environment