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Join Us at the American Chemical Society's Fall 2023 Meeting

Aug 1, 2023

We're proud to sponsor the American Chemical Society's (ACS) Fall 2023 Meeting, August 13-17, 2023, in San Francisco, California. Stone has been a longtime supporter of the ACS conference, and our employee-owners are eager to share another year's worth of experience in eight presentations across six symposia within the Division of Agrochemicals. Our scientists and modelers will cover diverse topics, including Unmanned Aerial Systems, off-target movement, ecological risk assessments, GLP field studies, and more.

In addition to our presentations, we are pleased to be a financial sponsor for two symposia: Data-Driven Approaches to Reduce Uncertainties in Water Exposure Assessments and Unmanned Aerial Systems (aka Drones): Pesticide Spraying and Other Agricultural Applications. 

For more information on our participation and to connect with our team at the conference, please see the details below.

Symposia and Presentations

Data-Driven Approaches to Reduce Uncertainties in Water Exposure Assessments

Sunday, August 13th | 8 a.m. - 12 p.m. (USA/Canada Pacific) | Session Type: Oral-Hybrid | Location: Room 3022, West Building (Moscone Center)

David Dreier (Organizer), Syngenta Crop Protection, Inc.; Michael Winchell (Organizer, Presenter), Stone Environmental, Inc.; Dr. Tharacad Ramanarayanan (Organizer, Presider), Syngenta Crop Protection, LLC; Yuzhou Luo (Organizer, Presider), California Department of Pesticide Regulation 

Stone is a proud financial sponsor of this symposium.  

#3920908 - Probabilistic Pesticide Usage Approach for New Uses and Its Application in Endangered Species Assessments (9:20 - 9:40 a.m.)

Hendrik Rathjens (Presenter), Michael Winchell, Stone Environmental, Inc.; Paul Whatling, FMC Corporation

Current methods used by the US EPA for conducting a spatial overlap between pesticide use sites and endangered species provide a conservative screening-level quantification of the co-occurrence between potential pesticide use sites with the ranges and critical habitats of listed species, especially for new uses of active ingredients. The overestimation in the co-occurrence quantification is mainly caused by the lack of field-specific pesticide application location information that leads the regulators towards making conservative assumptions on where pesticide usage occurs. This presentation introduces a methodology and presents results of a refined probabilistic spatial usage and overlay analysis that accounts for historical and projected usage. The refined overlay analysis was conducted on a subset of species ranges and critical habitats (CHs) to more accurately quantify co-occurrence between pesticide usage and species ranges and critical habitats and ultimately to better predictions of the likelihood that use of the pesticide may jeopardize the continued existence of the species or adversely modify its critical habitat. The methodology accounts for uncertainty in annual pesticide usage at the crop reporting district level by sampling from five different usage years. The uncertainty in pesticide application rates and area treated is accounted for by assuming both maximum and average reported annual application rates. Three different probabilistically generated ensembles of spatial usage footprints were generated in this study, one based purely on historical usage data and an assumption of average application rates, a second based on the same historical usage data and an assumption of maximum label application rates, and a third based on highly conservative projected usage assuming maximum application rates. Each of these three ensembles included 240 different usage footprint realizations, providing a robust distribution of possible spatial usage scenarios. A fourth ensemble of spatial usage footprints that included a 30 m offsite transport zone was created based on projected usage. The results show that screening level co-occurrence estimates can be greatly refined using a probabilistic approach. Ultimately, these usage distributions could be used within the US EPA’s current Biological Evaluation framework, providing a critically needed link between pesticide usage and model estimates of the magnitude and likelihood of exposure for a species.

#3928025 - Improvements to SWAT Model Channel System Pesticide Fate and Transport Processes (10:40 - 11:05 a.m.)

Michael Winchell (Presenter), Stone Environmental, Inc.; Natalia Peranginangin, Wenlin Chen, Syngenta Crop Protection, LLC 

Watershed scale modeling of pesticide concentration in flowing water bodies has become increasingly important in both surface water exposure assessments. Models that couple landscape and channel system processes can efficiently account for a heterogeneous landscape and the uniqueness of individual river segments. The Soil and Water Assessment Tool (SWAT and SWAT+) are such models that predict pesticide concentrations in flowing water bodies for watershed sizes from headwaters to continental scale rivers. The channel system pesticide fate and transport processes in SWAT account for movement of the pesticide in soluble and sorbed forms between the water column and the channel benthic layer and between connected reaches. The partitioning of pesticide between sorbed and soluble phases in the water column is conducted based on the pesticide sorption coefficient (Kd), the suspended sediment concentration, and the water volume in the reach segment, and follows equilibrium partitioning theory. SWAT then uses an empirical fixed rate constant approach to represent the transfer of pesticide from the water column to the channel benthic layer and from the benthic layer back into the water column. This approach effectively decouples sorbed pesticide transfer from suspended sediment settling and resuspension of deposited sediment but does not account for the equilibrium partitioning between the pesticide in the channel benthic layer and the water column. In this study, new pesticide channel process algorithms for SWAT, based upon EPA’s Variable Volume Water Model (VVWM), were developed to fully account for equilibrium partitioning across the sediment and water compartments in both the water column and benthic layers in SWAT reach segments. In addition, the simulated sediment transport dynamics were coupled directly to the sorbed pesticide mass balance across compartments and between reach segments. The new channel process algorithms were tested for low, medium, and high Kd pesticides and compared with both the original SWAT model and a VVWM representation of a single channel. The new model predictions align with conceptual expectations for the behavior of pesticides across a broad range of Kd values and match closely with VVWM predictions for a single flowing channel. The new model will provide significant improvements to the predictions of medium to high Kd pesticides in channel systems at the watershed scale without impacting predictions for low Kd pesticides.

Poster: Data-Driven Approaches to Reduce Uncertainties in Water Exposure Assessments (Tuesday, Aug. 15th, 12:00 - 2:00 p.m. at Hall A, South Building - Moscone Center)

David Dreier (Organizer), Syngenta Crop Protection, LLC, Michael Winchell (Organizer), Stone Environmental, Inc., Dr. Tharacad Ramanarayanan, Syngenta Crop Protection, LLC (Organizer), Raghavan Srinivasan (Organizer), Texas A&M 


Environmental Fate, Transport, and Modeling of Agriculturally-related Chemicals

Sunday, August 13th | 2:00 - 6:00 P.M. (USA/Canada Pacific) | Session Type: Oral-Hybrid | Location: Room 3016, West Building (Moscone Center)

Scott Jackson (Organizer, Presider), Envu; Ralph Warren (Organizer, Presider), BASF Corp.

#3923658 - Risk Assessment for Threatened and Endangered Bird Species in the United States Potentially Exposed to Clothianidin Seed Treatments (3:20 - 3:45 p.m.)

Dwayne Moore (Presenter), Stone Environmental, Inc.; Colleen Priest, Corteva Agriscience; Joseph Wisk, BASF Corp.

Under the Endangered Species Act, the US Environmental Protection Agency (EPA), National Marine Fisheries Service and Fish and Wildlife Service are required to assess the risks of pesticides undergoing registration or re-registration to threatened and endangered (listed) species. Currently, the EPA does not have a refined model for assessing the risks of seed treatments to listed bird species. Based on a review of the diets and foraging habitats of listed bird species and the locations of their ranges compared to crops where seed treatments could be used, we identified ten species that could possibly be exposed to pesticides through ingestions of treated seeds. The remaining listed bird species do not consume seeds and/or do not forage in agricultural areas. We developed the ESASeedPARAM (Endangered Species Assessment Seed Treatment Probabilistic Avian Risk Assessment Model) to incorporate species-specific diets, body weights and food ingestion rates. The model also incorporates information on the availability of waste grain for different crops and tillage practices, dissipation of seed residues following planting and metabolism and elimination by birds during and following exposure. The ESASeedPARAM specifically considers dietary exposure through the ingestion of pesticides-treated seeds. In this presentation, we describe a refined risk assessment for listed bird species conducted with the ESASeedPARAM for registered seed treatment uses of clothianidin including corn, cotton, soybean, rice, sorghum, canola, sugar beets and other cereal grains. Exposure estimates were highest for tilled fields because of the absence of weed seeds and waste grain that would contain negligible residue levels. Acute risk estimates were negligible for all species and use patterns for all tillage practices. Some exceedances of chronic no observed effect levels were found for tilled fields, but not for reduced and no till fields. Consideration of other lines of evidence and the inherent conservatism in the ESASeedPARAM suggest that risks to listed bird species due to the consumption of clothianidin-treated seeds are likely very low.

#3905333 - Measuring and Preliminary Modeling of Drift Interception by Plant Species (5:05 - 5:30 p.m.)

Jonnie Dunne (Presenter), Michael Winchell, Stone Environmental, Inc.; Shanique Grant, Jeffrey Perine, Stefan Wolf, Mark Ledson, Syngenta Crop Protection, LLC, Jeffrey Golus, University of Nebraska-Lincoln; Ian Whenham, SimuTech Group

Currently, the concept of plant capture efficiency is not quantitatively considered in the evaluation of off-target drift for the purposes of pesticide risk assessment in the United States. For on-target pesticide applications, canopy capture efficiency is managed by optimizing formulations or tank-mixing with adjuvants to maximize retention of spray droplets. These efforts take into consideration the fact that plant species have diverse morphology and surface characteristics, and as such will retain varying levels of applied pesticides. This work aims to combine plant surface wettability potential, spray droplet characteristics, and plant morphology into describing the plant capture efficiency of drifted spray droplets. Here we used wind tunnel experiments and individual plants grown to 10 – 20 cm to show that at two downwind distances and with two distinct nozzles capture efficiency for sunflower (Helianthus annuus) L., lettuce (Lactuca sativa) L., and tomato (Solanum lycopersicum) L. is consistently higher than rice (Oryza sativa) L., peas (Pisum sativum) L. and onions (Allium cepa) L., with carrots (Daucus carota) L. showing high variability and falling between the two groups. We also present a novel method for 3D modeling of plants from photogrammetric scanning and use the results in the first known computational fluid dynamics simulations of drift capture efficiency on plants. The mean simulated drift capture efficiency rates were within the same order of magnitude of the mean observed rates of sunflower and lettuce, and differed by one to two orders for rice and onion. We identify simulating the effects of surface roughness on droplet behavior, and the effects of wind flow on plant movement as potential model improvements requiring further species-specific data collection.


Back to the Basics: GLP Training for Study Personnel

SUnday, August 13th | 8 a.m. - 12 p.m. (USA/Canada Pacific) | Session Type: Oral-Hybrid | Location: Room 3014, West Building (Moscone Center)

#3927248 - Lessons From the Field: Common GLP Field Findings and How to Avoid Them (10:15 - 10:40 a.m.)

Jennifer Cypher (Presenter), Stone Environmental, Inc.

Field studies can bring unique GLP challenges for study personnel. This presentation will highlight ten common findings from my experience auditing GLP field studies. Specifically, we will learn about Quality Assurance Best Practices that can help you avoid findings like these and set you up for success as you encounter new challenges executing GLP work in the future.


Pesticide Runoff Mitigation: Characterization, Quantification, and Implementation

Monday, August 14Th | 2:00 - 5:35 P.M. (USA/Canada Pacific) | Session Type: Oral-Hybrid | Location: Room 3014, West Building (Moscone Center)

Huajin Chen (Organizer, Presider), Bayer CropScience; Patrick Havens (Organizer, Presider), Corteva Agriscience; Philip Janney (Organizer), Department of Environmental and Molecular Toxicology; Amy Ritter (Organizer, Presider), Waterborne Environmental, Inc. 

#3927195 - Development of a Multi-Tiered Stewardship Assessment Tool for Evaluating the Effectiveness of Field-level Conservation Practices in Reducing Off-field Pesticide Transport (2:55 - 3:30 p.m.)

Jody Stryker (Presenter), Michael Winchell, Stone Environmental, Inc.; Lula Ghebremichael, Tony Burd, Syngenta Crop Protection, Inc.

Emerging strategies for endangered species protection could entail targeted, field-specific mitigation strategies to manage pesticide exposure. Improved tools are therefore needed to quantitatively evaluate the impacts of field level practices for reducing off-field pesticide transport from agricultural lands, such as those that are known to reduce runoff, sediment, and nutrient losses. This presentation will describe a multi-tiered framework and demonstrate a prototype tool for implementing a scientifically defensible approach to quantifying the effectiveness of field-level conservation practices on pesticide losses and surface water pesticide concentrations. The tool utilizes the US Department of Agriculture (USDA) Agricultural Policy / Environmental eXtender Model (APEX), a well-established, physically-based model that predicts the short-term and long term impacts of agronomic management decisions on environmental quality and that is currently used to support the USDA Conservation Effects Assessment Project (CEAP). The Tier 1 workflow will support evaluation of conservation practices applied to standard Environmental Protection Agency (EPA) endangered species assessment (ESA) aquatic exposure scenarios. Tier 2 assessments evaluate effectiveness of practices for field(s) specific weather and soil inputs based on user defined field boundaries for any location in the continental United States. The tool provides estimates of soluble, sorbed, and total pesticide losses as well as benchmark outputs such as the fraction of applied lost in runoff and total pesticide loss off-field. This tool allows for consistent and standardized evaluation of conservation practice effectiveness in reducing pesticide losses, both at a generalized EPA’s scenario level as well as tailored to specific fields, and provides information on feasible, custom practice and management options to improve water quality outcomes necessary for endangered species protection.


Unmanned Aerial Systems (aka Drones): Pesticide Spraying and Other Agricultural Applications

Wednesday, August 16th | 8 a.m. - 12 p.m. (USA/Canada Pacific) | Session Type: Oral-Hybrid | Location: Room 3016, West Building (Moscone Center)

Ross Breckels (Organizer), Pest Management Regulatory Agency; Shanique Grant (Organizer, Presider), Syngenta Crop Protection, LLC, Zhenxu Tang (Organizer, Presider), Bayer Crop Science 

Stone is a proud financial sponsor of this symposium.  

#3917099 - Evaluation of a Mechanistic Model for Simulating Spray Drift From Unmanned Aerial System (8:55 - 9:20 a.m.)

Zenxu Tang (Presenter), Yaning Yang, Bayer Crop Science; Michael Winchell, Sebastian Castro-Tanzi, Stone Environmental, Inc.; Dr. Daniel E. Martin, Ph.D, USDA ARS Aerial Application Technology Research Unit; Brad Fritz, USDA

Recently, with the increased use and availability of unmanned aerial systems (UAS) for application of agrochemical sprays, a better understanding of spray drift from these platforms has emerged as a particular area of interest from many stakeholders. The approaches to better understanding off-target spray drift from UAS are being addressed from both field study and modeling perspectives. Field studies allows direct measurement of spay drift deposition from UAS under a range of environmental and application conditions, and this data is necessary to validate mechanistic models under development for the simulation of these emerging types of applications. Two independent field studies were conducted to evaluate spray drift for varied droplet sizes and application conditions using two different UASs. These field datasets were used to evaluate the predictions of spray drift deposition from a recently developed mechanistic model AGDISPpro to simulate in-swath and off-field drift and deposition from UAS agrochemical sprays. Customized UASs used in the field studies were incorporated in the AGDISPpro model and applied in the model simulations. The results of model predictions compared with field measurements will be presented, along with the sensitivity of the model simulation results to several input assumptions, including the parameterization of the UAS structural configuration and associated flow field.


Effect of EPA’s Endangered Species Enforcement on the Future of Agrochemicals

Wednesday, August 16th | 2:00 - 4:00 P.M. (USA/Canada Pacific)  | Session Type: Oral-Hybrid |Location: Room 3016, West Building (Moscone Center)

Phillip Cassidy (Organizer), Syntech Research; Huajin Chen (Organizer), Bayer CropScience

#3915425 - Automated Probabilistic Co-occurrence Assessments for Federally Listed Species in Aquatic and Terrestrial Domains (3:45- 4:10 p.m.)

Jonnie Dunne (Presenter), Hendrik Rathjens, Michael Winchell, Stone Environmental, Inc.; Max Feken, Richard Brain, Lula Ghebremichael, Tony Burd, Caydee Savinelli, Syngenta Crop Protection Inc.  

Section 7 of the Endangered Species Act requires the US Environmental Protection Agency to consult with the US Fish and Wildlife Service and National Marine Fisheries Service about potential pesticide impacts to federally listed species. However the abundance of registered products and listed species, and the lack of consensus on best available species distribution data and co-occurrence calculation methods make consultations laborious. In response to this issue we released the first version of the Automated Probabilistic Co-Occurrence Assessment Tool (APCOAT) in 2022. APCOAT is a freely available tool that generates batches of probabilistic maps and statistical summaries of species distributions, pesticide use, and co-occurrence between the two. Here we highlight the addition of the ability to conduct co-occurrence analyses in static and flowing aquatic domains in the second version of APCOAT. Pesticide use estimates and crop acreage statistics are used to first create Percent Crop Treated (PCT) maps. The PCT maps are then multiplied by probabilistic crop footprint rasters to produce the probabilistic pesticide use footprint rasters. For aquatic analyeses, pesticide usage probabilities are summarized by HUC12 watershed, and watershed connectivity is used to model upstream usage for affected waterbodies. APCOAT uses Maxent software to generate aquatic species distribution models (SDMs) based on occurrence records and models of bioclimatic predictor variables at the scale of National Hydrography Dataset flowlines (NHDPlus) and waterbodies. SDMs are constructed via an iterative model selection procedure that controls for known sources of error such as predictor variable correlation and prioritizes model fit. The probabilities of aquatic pesticide presence and aquatic species presence are then multiplied to compute probability of co-occurrence at the HUC12 level. Co-occurrence may also be calculated within larger zones of interest to aid in conservation planning. Accompanying automated reports detail the methods and input data used and summarize the range-wide co-occurrence, permitting rapid high-tier screening of species potentially affected by pesticides of interest. The results of our case study on co-occurrence between an herbicide and ten federally listed aquatic species illustrate a wide range of species extents, habitats, and co-occurrence statistics for both local and upstream pesticide usage.

Connect with Us During the conference

If you're also attending, join us for one of our presentations or contact Michael Winchell, John Hanzas, or Scott Teed directly to set up a time to connect.

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