### Appendix G. 

### TerrPlant Version 1.2.2 (December 26,2006): Model Description, Input, and Output for Spirotetramat
1. 

### Model Description TerrPlant was created by the Plant Technical Team and is used by the EnvironmentalFate and Effects Division (EFED) as a Tier 1model for screening level assessments ofpesticides. Themodel is implemented in Microsoft Excel. The purpose of TerrPlant is to provide screening level estimates of exposureto terrestrial plants from single pesticide applications. The model does not consider exposures to plants from multiplepesticide applications. TerrPlant derives pesticide EECs in runoff and in drift. RQs are developed for non-listed and listed species ofmonocots and dicots inhabiting 

### dry and semiaquatic areas which are adjacent to treatment sites. 2. 

### Model History
TerrPlant was originallyused in EFED in 2002 as version 1.O. The model was developedto automate existingmethods for calculating RQ values for non-listed and listed terrestrial plants, includingwetland species (USEPA 2002a). 

### In 2005, TerrPlant was modified to v1.2.1 to remove an assumptionthat aerial applications result in 60% application efficiency. TerrPlant v1.2.1 assumed 100% efficiency in ground and aerial applications (USEPA 2005). The current model version (1.2.2) includes the same assumptions and equations as v1.O, with the exception ofthe application efficiency assumption for aaial applications. TerrPlantv1.2.2 represents a cosmetic update of v1.2.1. No model assumptions or equations were altered from v1.2.1. Version 1.2.2 automates the calculation of EECs and RQ values accordingto current EFED guidance. 3. 

### Conceptual models TerrPlant incorporatestwo similar conceptualmodels for depicting 

### dry and semi-aquatic areas of terrestrial habitats. For both models, a non-target area is adjacent to the target area. Pesticide exposures to plants in the non-target area are estimatedto receive runoff and spray drift from the target area. For a 

### dry area adjacent to the treatment area, runoff exposure is estimated as sheet runoff. Sheet runoff is the amount ofpesticide in water that runs off ofthe soil surface of a target area of land which is equal in size to the non-target area (1:1ratio of areas). For semi-aquatic areas, runoff exposure is estimated as channel runoff. Channel runoff is the amount ofpesticide that runs off of a target area 10 times the size of the non-target area (10: 1ratio of areas). Exposures through runoff and spray drift are then compared to measures of survival and growth (e.g. effects to seedling emergence and vegetative vigor) to develop RQ values. 4. 

### Calculationof EECs
In TerrPlant v1.2.2, user inputs for EECs are indicatedby 

### green text and are located in 

### Tables 1 

### and 2. 

### Table 1 containsreference information for the user which is relevant to the identity and use ofthe pesticide but does not directly affect EEC calculations. 

### Table 2 is used to input parameter values for deriving drift and runoff EECs. Inputs and results for spirotetramatare found in 

### Tables 1-5,below.In cases where multiple application methods (ground and aerial/airblast/spraychernigation) and/or application forms (liquid and granule) are possible for a pesticide, multiple drift fractions are possible for

n n~ctiriil~ Thic imnnrtc the ralmlatinn nf FFT'c nf the nectiriile Tn ralmlatp the different FFC's and y""" "'"" "'---I-'"'-"-'- 

# - y""""'"v. """ 

# -" r- 

## ---. -- 11-1 

## --" resulting RQs for the different possible drift fractions, the user should completethe following steps: 1) input all relevant data for the pesticide accordingto one relevant type of application method and form (Tables 1,2and 4); 2) copy the worksheet within the Excel file; 3) alter the relevant application method andlor form to represent another application scenario; and 4) repeat as necessary. 

### In Table 2, the application rate shouldbe entered in units which are consistent with units ofplant survival and growth data entered in Table 4 (e.g. lbs a.i./A, lbs a.e./A). This value represents the maximum rate per single applicationaccording to the label. If multiple applications are allowedby the label, only the application rate per single applicationshouldbe entered,not the total annual application rate. The incorporation value is based on the depth ofpesticide incorporationin inches. Incorporation depth is dependentupon label directions. In TerrPlant, this value is unitless and is related to the proportion of applied pesticide which is available for runoff. The default value for this parameter is 1,which is entered for ground applications with no incorporation and for aerial applications.When the incorporation depth is >1 inch, the specifiedvalue is entered. If the value is > 

### 6 inches, 

### 6 should be entered. In cases where labels give a range of incorporation depth, the user should model RQs resulting fromboth the minimum and maximum depths as indicated by the label. The magnitude ofrunoff is assumedto be dependent on the water solubility ofthe pesticide active ingredient. For pesticides with a solubility of 40, 10to 100, or >I00 ppm, runoff fractions of 0.0 1,0.02 or 0.05 respectively (Aquatic Effects Dialogue Group 1992), are selectedby the model user. It is assumed that, for 

### a liquid formulated pesticide appliedby ground methods, 1% ofthe applied mass of pesticide per acre will drift to the non-target area. For a liquid formulated pesticide which is applied through aerial, airblast or spray chemigation methods, 5% of the applied mass ofpesticide per acre will drift to the non-target area 

### (USEPA 2002). In cases where a pesticide is in granular form, drift is assumed to be 0%. Runoff exposureis assessed in two scenarios: sheet and channel runoff. In the sheet runoff scenario, the treated area generating runoff is assumed to drain into an area with equal sizecontaining seedlings, resulting in 1,2,or 5% ofthe application rate being deposited. In the channel runoff scenario, a ten-toone ratio of watershed area to receiving area results in 10,20,or 50% ofthe applicationrate being deposited on soil with emerging or emerged seedlings. With pesticides which are ground incorporated, the runoff EEC is decreased because the applicationrate is dividedby the incorporation depthbefore being multipliedby the runoff value. For RQ derivation,EECs for dry and semi-aquatic areas combinerunoff and drift exposures. Drift only EECs are also used for RQ derivation (Table 3). All EEC values are in units consistent with those enteredby the user for application rate (Table 

### 2).

5. ToxicityData Data from submitted seedling emergence and vegetative vigor studies areused to establish the toxicity of a pesticide to monocots and dicots. The ECz5 values of a pesticide for the most sensitive tested monocot and dicot species are used to definethe toxicity ofthis pesticide to non-listed species. The corresponding NOAEC values (or ECo5 if a suitable NOAEC is unavailable) for the same species and endpoint are used to define the toxicity of thepesticide to listed plants (USEPA 2005b) (Table 4). Units for toxicity data must be consistent with applicationrate units.



### 6. RQ values TerrPlant derivesRQ values for non-listed and listed species ofmonocots and dicots inhabiting dry and semi-aquaticareas. The model comparesthe combined deposition estimates fiomrunoff and spray drift to adverse effect levels measured in seedling emergence studies. RQs (Table 5) are derived by dividing the total EEC (Table 3) by the relevant seedling emergence value (Table 4).

Monocot non-listed <0.1 <0.55 0.13 

# I

*If RQ > 1 .O, the LOC is exceeded, resulting in potential forrisk to that plant group. 

# I Monocot

Dicot Dicot

In addition, RQs are derived for plants with consideration for spray drift exposures. For monocots and for dicots, TerrPlant compares estimated spray drift deposition, without a runoff exposure component,to the more sensitivemeasure of effect, either seedling emergenceor vegetative vigor (USEPA 2005b). The selection of the more sensitivemeasure of effect is automated by the model and is defined by the lowest EC25value. The associatedNOAEC value is selectedto define RQ values for listed species exposedto listed non-listed listed 0.1 <0.1 0.1 0.55 <0.55 0.55 0.40 <0.1 <0.1

### drift. 

### Incases where the ECZ5 values for seedling emergence and vegetative vigor studies are equal, the lowest NOAEC value is selected in calculation ofthe RQ value. The results ofthese calculations are RQ values for non-listed and listed monocots and dicots inhabiting adjacent and semi-aquatic areas and exposed to 

### drift only (Table 5).
In TerrPlantv1.2.2, if a RQ value is <0.1, the model automatically indicates "<0.1" as the RQ.


### 7. LOC EFED's LOC for non-listed and listed plant species is 1.0.RQ values exceeding 1.0 indicate potential risk to plants. RQ values less than or equal to 1.0indicatethat potential risk is minimal. 

### In other words, if pesticide exposure (EEC) does not exceed the toxicity value (ECz5 or NOEC), the RQ is 51.O. This places the RQ below EFED7s LOC and potential risk to that plant group is consideredto be acceptable. 

### 8. Discussion of Assumptions and Uncertainties TerrPlant7s10to 1 ratio oftarget area to semi-aquatic non-target area is based on research indicating a pond located in Georgia with a 6-7 foot typical depth and a requirement of 2 acre drainage areas per foot of depth (USDA 1997). Althoughthe data are derived from observations of aquatic areas (e.g. farm ponds), it is assumed that this ratio is relevant to low-lying semi-aquatic areas. There is some uncertainty associated with the depth ofthe ponds used for modeling purposes and the expected depth of a semiaquatic area. Consistent with a screening level approach,the application efficiency, which is the amount of applied pesticide reachingthe target area, is assumed to be 100% for all applications. Application efficiency is considered separately from spray 

### drift; where the sum of the two does not necessarily equal 100%. Spray 

### drift is estimated based on application method alone, without consideration of other potentially influential factorsrelated to application, such as droplet size, wind speed and release height. The model assumption that granular applications have 0% spray 

### drift may result in an underestimation of exposure. TerrPlant assumes that 

### drift and runoff concentrations are uniform/over the non-target area. 

### In the field, decreasing concentrationgradients would be expected for each ofthese exposure pathways as the distance increases fromthe application site. If the dimensions (i.e. length and width) ofthe target area and nontarget area where defined, the uncertainties associated with these assumptions could be explored. For pesticides that involve ground incorporation applications (> 1 in), less of the pesticide applied is vulnerableto runoff. 

### In TerrPlant, the application rate is dividedby the incorporation depth. The basis for calculation of effects of ground incorporation on pesticide runoff also originated fi-omformer assumptions related to modeling aquatic EECs. The assumption is that the incorporation depth in inches is directly related to the proportion of runoff. For example, incorporation of a pesticide to a depth of 2 inches would result in % ofthe application rate being available for runoff. This proportion is considered relevant up to 6 inches. Thus, the model assumes that the amount of pesticide in runoff is directly related to the depth to which the pesticide is incorporated into the ground. There are several assumptions related to temporal factors of exposure and effects. 1) The model assumes that pesticide contained in drift and runoff reaches the non-target area at the same time. This assumption is conservativebecause it is unlikely that a pesticide would move at equal rates in 

### drift and runoff. 2) The model does not consider the coincidence of 

### drift pesticide and runoff pesticide reaching the non-targetarea in time to reach the emergenceportion ofthe plant's life cycle. If applied later in the plant's life cycle, it is possible that the pesticide will reachthe non-targetplants at stages of different sensitivities.It is uncertain whether or not 

### an exposure which occurs at a different life stage of the plant is relevant to the RQ derivedbased on the early seedling stage of a plant's lifecycle (i.e. this may have greater or lesser effectthan indicated by the RQ). Modeled pesticide concentrations in runoff are dependent solely upon solubility ofthe pesticide. The amount ofpesticide in runoff does not consider other relevant transport properties of the pesticide (e.g. &). In addition,the model does not consider pesticide movement through the soil or contained in eroded soil. The model does not incorporate parameters that would allow for photolytic, hydrolytic or microbial degradation.

### In cases where degradation occurs, this leads to an uncertainty in the amount of pesticide that would be present in runoff and in 

### drift. The RQ values which are currently derivedby TerrPlantrepresent the risk of effects for singlemaximum applications. It is assumedthat each single applicationwould expose different plants (i.e. due to different drift patterns). The modeling of EECs from singlepesticide applications rather than multiple applications could result in underestimating pesticide exposuresto plants. For defining RQ values for plants exposed to runoff, measures of effectto seedling emergence are used; however, vegetativevigor could be affected by runoff (i.e. effects to plant roots). Due to limitations of testing methods, these effects are not measured and cannot be incorporated into RQ development. There is an absence of data comparingthe field concentrations ofpesticides to EECs generated by TerrPlant. Therefore,the relevance of TerrPlant predictions to pesticides concentrationsin the field is unknown.
9. 

### References Aquatic Effects Dialogue Group. 1992. Improving Aquatic Risk Assessment Under FIFRA. Report of the Aquatic Effects Dialogue Group. RESOLVE, An Independent Program of World WildlifeFund. SAP. 2001. ScientificAdvisory Panel Briefing: Proposal to update non-target plant toxicity testing under NAFTA. Joint presentationby Health Canada and USEPA. June 27-29,2001.
USDA. 1997. Ponds -Planning, design, construction. United States Department of Agriculture. Issued June 1992. Revised November 1997. Agriculture Handbook 590.Available online at: http://www.in.nrcs.usda.gov/pdfo/o20fdes/PONDS.PDF. USEPA. 1996.Ecological effects test guidelines. OPPTS 850.4000. Background -Nontarget plant testing. United StatesEnvironmental Protection Agency. EPA 712- C-96-151. Online at: http://www.epa.gov/oppts~s/publications/OPPTSHonize85OEcolocalEffects~Test~Guidelines /Drafts/850-4000.pdf. USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the EnvironmentalFate and Transport of Pesticides, Version 

### II. US Environmental Protection Agency, Washington DC. Environmental Fate and Effects Division. Online at: http://www.epa.gov/oppefedl/models waterlinputsidance2-28-02. htm.USEPA. 2002a. EFED Policy Memorandum: automationof Environmental Exposure Concentrations (EECs) and Determinations of Risk Quotients (RQs) for Terrestrial Plants Using TerrPlant Model (version 1.0). United States Environmental Protection Agency, Office ofPesticidePrograms. October 16, 2002. USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of PesticidePrograms. U.S. Environmental Protection Agency, Office ofPrevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington DC. 100 pp. January 23,2004.
USEPA. 2005. Memorandum: policy guidanceto removethe 60% application efficiency factor from aerial applicationsexposure estimates in TerrPlant. United States Environmental Protection Agency, Office ofPrevention,Pesticides and Toxic Substances. October4,2005. USEPA. 2005a. Memorandum: clarification of plant evaluation guidance. United States Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances. October4,2005.