Accurate Modeling for Drift Reduction: General Overview and Regulatory Status

1. Accurate Modeling for Drift Reduction:General Overview and Regulatory Status April 11th, 2014 Dan Dyer On Behalf of the CLA Spray Drift Issue Management Team

2. Spray Drift Regulation • Spray drift is complex… • Ground, aerial, orchard/airblast sprays • Broad range of technologies of spray equipment • Significant differences in geography/climate • Conservative drift models (perceived drift issue) • But can be well managed… • Local applicators/growers understand appropriate conditions for application and minimizing drift • Training / certification / education • Pesticide Label Restrictions – wind speed, buffers, etc. • Newer drift reducing technologies

3. Spray Drift Regulation • Recently released spray drift guidance for use of AgDRIFT in human and ecological exposure/risk assessment • EPA-HQ-OPP-2013-0676 “Consideration of Spray Drift in Pesticide Risk Assessment” • CLA supports development of appropriate drift assessment methodologies • However, EPA guidance is too restrictive and is limited in ability to make higher tier refinements

4. Factors Influencing Spray Drift • Spray Characteristics • Droplet size • Chemical / Formulation / Adjuvants • Equipment & Application • Nozzle type, size, orientation • Nozzle pressure • Height of release • Weather, etc. • Air movement (direction and velocity) • Temperature & humidity • Air stability/inversions

5. Droplet Categorization - ASABE Need to select droplet size to maximize efficacy and minimize drift From: ASABE Standard S-572.1

6. AgDRIFT to Calculate Buffers • EPA 2014 guidance uses AgDRIFT to determine drift for terrestrial (plant/animal) and aquatic habitat • AgDRIFT based on Spray Drift Task-force data • 48 unique SDTF Deposition Datasets • Excellent quality & GLP • Used older (1992-93) spray application technology • Several conservative approaches result in unrealistic ground drift estimates • Unable to refine drift estimation using drift reducing technologies (DRT) and best management practices

7. AgDRIFT – Overestimation of Drift • AgDRIFT produces unreasonably conservative drift estimates when compared to existing drift data sets Figure Courtesy J. Wright

8. AgDRIFT – Scale-up Overestimation • SDTF Data is foundation for AgDRIFT, but use of multipliers to scale-up to a ‘typical’ field is much too conservative • 90th %ile curves inappropriate • Gross overestimate at far-field distance Figure Courtesy J. Wright

9. 2011 AAFC Data – Multiple Swaths • Dr. Tom Wolf of Agriculture and Agri-Food Canada (AAFC) developed drift dataset as basis for PMRA buffer zone calculator • No significant deposition after 4-5 swaths (~250-300 ft)

10. AgDRIFT – Overestimation of Drift Nozzle Trial “Data Lumping” • In AgDRIFT, SDTF data was consolidated into two categories: • Inappropriate to evaluate medium or coarser sprays • Inadequate for current nozzle technology Very Fine to Fine Fine to Medium/Coarse

11. Nozzle Types Flat Fan Nozzles Air Induction Nozzles

12. AgDRIFTWind Speed “Data Lumping” • Drift at distance, is influenced by data generated in high wind (25% of SDTF ground data with >20 mph wind!!) • 90th percentile could be ‘off-label’

13. AgDRIFT – Overestimation of Drift • Summary • Mathematical model used in AgDRIFT to describe the conservative 90th percentile drift curves are subjective, and overestimate drift • ‘Best fit’ curves in AgDRIFT never intersect zero • Lumping of data for trials with different nozzles (spray quality / droplet sizes), and wind speed produces excessive overestimates* of drift from ground sprays, and removes capability to refine model • * in some circumstances AgDRIFT can predict movement of more off-target material than the amount applied

14. Drift Overestimation – The Impact? • AgDRIFT used to calculate proximity distances and buffers for FIFRA ecological and human health risk assessments, and Endangered Species Risk Assessments • Appropriate for ‘screening’ assessment, but requires refinement options • Risk should be refined before buffer size is determined (mitigation)

15. Large Action Areas(Endangered Species) • Spray Drift – 360 degrees, wind blowing in all directions, simultaneously • Threshold’ = EEC / LOC • EEC from AgDrift Significant overestimate of action area and potential buffer distances

16. Drift Overestimation – Impact on Agriculture • Impact on agriculture (example) • ~600 feet of field or parts of field cannot be treated

17. Drift Overestimation –Impact on Agriculture • ‘Freedom to operate’ for grower • Possible need to remove land from production as more buffers and larger buffers are required (value / cost?) • Cost effectiveness of having to use ground applications instead of aerial • Resistance Development • Cutting rates to meet buffer requirements • No applications to certain parts of field • Incomplete coverage due to coarser spray droplet

18. Spray Drift – A Pragmatic Solution • Need to find appropriate balance between efficacy, drift and resistance management, to allow cost-effective pest control. • Model refinement is necessary – reasonable conservatism • ‘Drift education’ / Best Management Practices are critical • Automation is desirable to allow flexibility

19. REGDISP • Model built on AGDISP (v. 8.26) • USFS made code available to Industry • the current EPA accepted version of AGDISP • desire to keep the mechanistic ground model • No changes to existing AGDISP code existing • Better interface for AGDISP calculators • Enables parsing of data/ addition of data • Addresses issues with AgDRIFT described 19

20. Canada Drift Regulation • Pest Management Regulatory Agency in Canada worked with Dr. Tom Wolf of Agriculture and Agri-Food Canada (AAFC) and developed their own dataset as basis for their buffer zone calculator • Launched in 2011

21. REGDISP Data Sets • Agricultural Agri Food Canada (AAFC) ‘2000 • Agricultural Agri Food Canada (AAFC) ‘2004 • Agricultural Agri Food Canada (AAFC) ‘2011 • 49 unique AAFC Deposition Datasets • Spray Drift Task Force ‘1992 • Spray Drift Task Force ‘1993 • 48 unique SDTF Deposition Datasets • 97 unique deposition datasets 21

22. Canadian Field Study Design (‘00 and ‘04) XR8001, XR8003, AI110025, AI11005, AI11004 Nozzles Fine to V. Coarse sprays 60 and 90 cm boom heights Wind speed = 3 to 12 m/s Single pass, 18m (60 ft) spray boom

23. Data Fit Method Log/Log Transform Data Since Deposition Data is highly non-linear Log Transform Simple Regression (y=mx+b) • Accurate description of data • Doesn’t assume drift is unlimited 23

24. Deposition Data Calculation Tab Select Dataset Select Nozzle Boom Height Wind Speed Enter Rate Run 24

25. Use Existing Calculators (and Code) Toolbox 25

26. Consideration of DRTs in Risk Assessment • DRTs are proposed for use in reducing the size of required buffers • Promote Best Management Practices (BMPs) • Recommendations for specific Spray Quality or Droplet Size likely needed to ameliorate ESA restrictions – and maintain a viable product • REGDISP facilitates consideration of specific field data or combinations of DRTs in determining a suitable action area or buffer distance

27. Pragmatic Approach to Spray Drift • Use of REGDISP as conservative, yet realistic drift model • No ‘infinite’ drift • Ability to refine ground spray drift estimates – spray quality, wind, DRTs, BMPs, etc. • Defines reasonable proximity/buffer distances to expedite FIFRA and endangered species risk assessments • Education / Stewardship • Promote Best Management Practices • CropLife, chemical producers, nozzle manufacturers, product distributors, retailers, etc. • Ag extension, federal/state agencies, universities • Continued research

28. Pragmatic Approach to Spray Drift • Use of automation of spray technology • e.g. GIS on conjunction with automated nozzle switching allows precision application with respect to buffer areas • Need to provide spray drift options that growers and applicators can use today to: • allow safe use of products (human and ecological), • without unduly impacting growers’ ability to effectively produce crops

29. Thank you