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We are headed to Fort Worth, Texas, to participate in the Society of Environmental Toxicology and Chemistry's (SETAC) 45th Annual Meeting.

The meeting is a five-day event that features training, networking, collaboration, and learning opportunities, with a focus on emerging research, regulatory developments, and the latest methodologies in environmental toxicology and chemistry. Our employee-owners will be sharing a variety of oral presentations and posters, as well as a short course. 

Click here to register and learn more.

If you're also attending, join us for one of our presentations or contact Michael Winchell, Dwayne Moore, or Alan Samel directly to set up a time to connect.

short course

PT01 Using Freshwater Invertebrates for Toxicity Tests – Study Design, Culturing, Test Methods, Data Interpretation

Time: 8 a.m. to noon, CDT, Sunday, October 20

Location: Texas A (2, Omni Fort Worth Hotel)

Authors: Alan Samel (Stone Environmental), James M. Lazorchak (U.S. Environmental Protection Agency)

Freshwater Invertebrates are a diverse group of organisms that can be tested under laboratory conditions and in the field under more realistic exposure conditions.  Under regulatory frameworks for effluent and receiving waters, the ‘core’ studies with aquatic freshwater invertebrates in the U.S. are limited to acute studies with 3 species of cladocerans (Daphnia magna, D. pulex, and Ceriodaphnia dubia), and chronic laboratory tests with one species of cladocerans, C dubia and in sediments the midge (Chironomus dilutus) and the amphipod (Hyalella azteca) are often required. For pesticide registration, the Daphnia magna (or D. pulex) acute toxicity and D. magna reproduction tests are considered core studies. Acute and chronic toxicity tests with C. dilutus and H. azteca may also be required, depending on certain triggers.  Toxicity tests can range from static acute toxicity tests assessing survival to chronic flow-thru laboratory tests assessing survival, growth, and reproduction studies to community studies with mesocosms, lakes and flowing water systems.  Tests with aquatic invertebrates in the lab and the field can provide answers to questions pertaining to the sensitivity of these organisms to external stressors (pesticides, heavy metals, etc.) and mixtures (effluents and receiving waters).

*you must pre-register to attend this course.

 

Oral Presentations

5.02.A.T-03 Automated Probabilistic Spatial Co-Occurrence Assessments for Aquatic Endangered Species

Time: 10:40 a.m. CDT Wednesday, October 23

Location: 202 CD (Fort Worth Convention Center)

Authors: Jonnie Dunne, Hendrik Rathjens, Michael F Winchell (Stone Environmental), Max Feken, Tony Burd, and Richard Brain, (Syngenta Crop Protection)

The Endangered Species Act requires the U.S. Environmental Protection Agency to consult with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service over potential impacts of pesticides on federally listed species. The deterministic methods currently used to analyze the spatial co-occurrence of endangered species and pesticide applications do not account for the spatial and temporal variability of either phenomenon, or the uncertainty inherent in modeling them. Probabilistic methods that account for variability and uncertainty to improve the accuracy of co-occurrence assessments have been recommended by the National Research Council but have not yet been implemented due to the higher complexity of the calculations and the volume of additional data required. The Automated Probabilistic Co-Occurrence Assessment Tool (APCOAT) provides access to both the data and methods required to rapidly conduct probabilistic spatial co-occurrence analyses and can be used to facilitate the transition from deterministic to probabilistic co-occurrence analyses. Here, we use APCOAT to study the potential co-occurrence between aquatic endangered species and atrazine applied to corn in the continental U.S., when considering both in-watershed and upstream pesticide usage. We modeled flowing aquatic habitats (rivers and streams) for 189 species drawing from a pool of 197 environmental variables, and static aquatic habitats (ponds and lakes) for 29 species drawing from a pool of 148 environmental variables. Species habitat models (SHMs) were generated iteratively, with variables being removed on the basis of correlation with other variables and contribution to the model, while minimizing reductions to model fitness as measured by the area under the receiver-operator curve (AUC, the chance that a randomly selected species presence location is ranked higher than a randomly selected background location). The resulting SHMs show high model fitness and parsimony, with flowing habitat SHMs having AUC of 0.86 - 0.99 (median 0.99) based on a median of 8.5 environmental variables, and static habitat SHMs having AUC of 0.92 – 0.99 (median 0.99) based on a median of 5 environmental variables. Across all species, habitat types, and pesticide transport methods, 65% of co-occurrence analyses showed < 5% probability of co-occurrence, 9% of analyses showed 5% - 10% probability of co-occurrence, and 26% of analyses showed >10% probability of co-occurrence.

5.02.B.T-02 Evaluating Field-Specific Pesticide Runoff and Erosion Mitigation Need and Mitigation Practice Effectiveness Using the Pesticide Mitigation Assessment Tool (PMAT)

Time: 1:50 p.m. CDT, Wednesday, October 23 

Location: 202 CD (Fort Worth Convention Center)

Authors: Michael F Winchell, Jody Stryker (Stone Environmental), Tony Burd, Richard Brain (Syngenta Crop Protection LLC), Lula Ghebremichael (Bayer Crop Science), Jane Tang (Bayer AG - Crop Science Division), Robin Sur (Environmental Safety, Bayer AG - Crop Science Division, Germany) and Tilghman Hall (Bayer CropScience LLC)

Mitigations are now being required by regulatory authorities in the US as an a priori mechanism to offset potential risks posed by the use of agricultural pesticides to “listed” (threatened and endangered) species. Mitigation requirements have been proposed to reduce off-site pesticide transport via both spray drift and runoff/erosion processes. The runoff and erosion mitigation options available to growers provide some flexibility in meeting the requirements for pesticide use; however, the current process includes limited consideration for field-specific conditions that would guide mitigation selection. Determining both the level of mitigation required and the effectiveness of mitigation options is challenging but necessary given the proposed regulatory framework. Many site-specific factors contribute to the variability in both requirements and effectiveness, including weather conditions, soil characteristics, topography, and cropping systems. While generalized mitigation requirements and effectiveness assumptions can be made and implemented into a regulatory framework with beneficial results, the advantages afforded by a site-specific mitigation effectiveness assessment make a compelling case for adopting such an approach. The Pesticide Mitigation Assessment Tool (PMAT) is a site-specific agronomic modeling tool that predicts pesticide runoff and erosion from agricultural fields based on site-specific conditions. Based on the USDA-supported APEX model, PMAT evaluates both the mitigation requirements for a field and the mitigation effectiveness of a range of common agricultural conservation practices, including combinations of mitigation practices. PMAT automatically evaluates the effectiveness of all feasible mitigation practice combinations, providing the user with a menu of options that meet the requirements for pesticide use and protection of endangered species. The site-specific approach offered by PMAT enables more efficient use of conservation resources, guiding the appropriate level of mitigation and avoiding unnecessary changes in agricultural practices when ecological protection goals are already met. An example application of PMAT will be provided with a case study context.

 

Poster Presentations

4.03.P-Mo-073 - A Biological Option for Control of Varroa Mites in Honeybee Hives

Time: 8-10 a.m., CDT, Monday, October 20

Location: Exhibit Hall, Fort Worth Convention Center

Authors: Dwayne R.J. Moore (Stone Environmental), Miriam Frugis, Laurent Mezin (Greenlight BioSciences Inc.)

Varroa mites are a serious pest of western honeybee colonies and a primary reason behind the large colony losses reported by beekeepers in recent years. Varroa mites are an external parasite that feed on adult bees and developing honey bee larvae. In addition to directly affecting bees, the mites are also vectors of several viruses that can kill bees. The traditional method for varroa mite control has been to hang plastic strips impregnated with synthetic pesticides in the hive (e.g., fluvalinate, amitraz, coumaphos). Repeated use of these pesticides has led to mite resistance, decreasing their effectiveness. Other options for controlling varroa mites such as mechanical methods (e.g., drone-brood trapping), use of mite-tolerant honeybee stocks, and natural pesticides (e.g., formic acid) may be helpful but have not provided consistent protection. Recently, a double-stranded RNA product, EP15 (vadescana), was developed to control varroa mites in honeybee hives by blocking the expression of calmodulin protein in reproductive mites through the RNAi mechanism. EP15 has a nucleotide sequence specific to the calmodulin messenger RNA of varroa mites and thus exhibits little to no cross-toxicity to other organisms. EP15 is formulated as a sugar solution in a perforated pouch that is placed inside the honeybee hive in the spring and fall. We conducted a risk assessment that demonstrated that EP15 poses negligible risk to honeybees in treated hives. The available fate and ecotoxicity studies showed that EP15 residues outside the hive are at very low concentrations, and what little EP15 is available outside the hive is rapidly degraded. We thus conclude that the EP15 formulation is a safe and effective tool for control of varroa mites in honeybee hives.

3.03.P-Th-029 - Accounting for Uncertainty in Pesticide Risk Assessments for Wildlife: Approaches at Different Tiers

Time: 8 to 10 a.m., CDT, Thursday, October 24

Location: Exhibit Hall, Fort Worth Convention Center

Author: Dwayne R.J. Moore (Stone Environmental)

In the United States (US) and elsewhere, wildlife risk assessments for pesticides should follow a tiered approach. The initial screening-level assessment is based on simple, highly conservative models (e.g., T-REX, T-HERPS for birds, mammals, herptiles in the US). Such models assume, for example, that wildlife forage exclusively on treated fields immediately after application and are exposed to 95^th percentile concentrations on dietary items. Although useful for determining which receptor group and use pattern combinations are a potential risk concern and those that are not, relying solely on these models without a corresponding uncertainty analysis presents a distorted risk picture. This distorted risk picture is problematic because the US Environmental Protection Agency (EPA) only infrequently conducts higher tier, probabilistic assessments even when potential risk concerns are identified for wildlife. As a result, the Agency is often sued when pesticides are registered or re-registered because it’s own analyses indicated risk quotients that exceeded levels of concern for wildlife. The obvious solution would be to conduct more realistic and probabilistic assessments for scenarios identified as being potential risk concerns in the screening-level assessment. However, the EPA has resource limitations, thus limiting their ability to routinely conduct higher tier assessments for wildlife. In this presentation, I will discuss simple steps that may be taken to account for uncertainty in screening-level assessments that require few additional resources but result in a more accurate risk picture for wildlife. Examples include: (i) conducting best-case and most likely analyses alongside the typical worst-case analyses, (ii) creating generic probabilistic models for a suite of wildlife receptor groups that have standardized distributions for key parameters such as food ingestion rate, dietary residue concentrations, and rates of degradation and metabolism, and (iii) conducting what if analyses for parameters that are uncertain (e.g., proportion time foraging an and off treated fields). When higher tier assessments are required, other refinements such as the use of species-specific, spatially explicit exposure models and dose-response curves can be incorporated in wildlife assessments for pesticides. The latter are resource intensive and thus unlikely to be conducted on a frequent basis.

5.15.P-Th-074 - A Higher-Tier Field Spray Drift Bioassay Concept to Evaluate Herbicidal Effects to Non-target Plants

Time: 8-10 a.m., CDT, Thursday, October 24

Location: Exhibit Hall, Fort Worth Convention Center

Authors: Dwayne R.J. Moore, Jacob Mitchell, Rachel Lightfoot, Ben Brayden, John Hanzas (Stone Environmental) Richard Brain (Syngenta Crop Protection LLC)

The United States Environmental Protection Agency (USEPA) uses a tiered risk assessment framework to evaluate the potential effects of pesticide active ingredients to non-target organisms. Predictive models such as AgDRIFT® are used at the screening-level to conservatively generate downwind off-field exposure estimates via drift deposition curves. The most sensitive regulatory endpoints, i.e., the effective rate required to affect 25% of individuals (ER25) for non-listed species or the no-observed effect rate (NOER) for listed species, derived from standard guideline vegetative vigor (OCSPP 850.4150) and seedling emergence (OCSPP 850.4100) studies are then benchmarked against these curves. The point at which the regulatory endpoint falls below the corresponding exposure estimate on the drift curve(s) is used to inform the in-field no application zone or ‘buffer’ to ensure protection of downwind sensitive plants. The fundamental issue with this approach is that it assumes that non-target plants are exposed as would be in-field target weeds, which they are not. In standard guideline studies, test plants are exposed in a chamber via a track sprayer that delivers a direct overhead spray intended to saturate the foliage or soil surface (i.e., full coverage). Conversely, non-target plants do not receive even herbicide coverage on the foliage because spray drift is more likely to contact the upwind (via lateral interception) and top (via deposition) portions of the foliage. In addition, numerous properties of the downwind plant community (e.g., plant density and height, drag characteristics of the foliage, collection efficiency) influence exposure of non-target plants to herbicide drift. What does this mean for farmers in a regulatory context? The results of recent field studies in which non-target plants were placed at different distances downwind of herbicide applications indicate that buffers derived under the current USEPA paradigm are overestimated by 10- to 100-fold. Such unnecessary drift mitigation buffers result in large parts of fields being untreated and, as a result, lower yields. In this presentation, we explore alternative approaches for deriving spray drift buffers for herbicides including a weight of evidence approach that considers all available and relevant information.