Supporting Information

Fate and transport of furrow-applied granular tefluthrin and seed-coated clothianidin insecticides: Comparison of field-scale observations and model estimates

Kara E. Huff Hartz, Tracye M. Edwards, and Michael J. Lydy*

Center for Fisheries, Aquaculture, and Aquatic Sciences, and Department of Zoology

Southern Illinois University Carbondale

Carbondale, IL USA

Methods

Field site description and field insecticide concentration measurements

Standard farming practices were used and included the application of nitrogen, potassium, and phosphorus prior to spring planting, and post-emergence and burn-down application of herbicide to control weeds. Tefluthrin and clothianidin insecticides were applied each year at sowing. Clothianidin-coated maize seed was planted using a John Deere 1770NT 24 row planter (Moline, IL, USA) using the pneumatic down force system, with 76 cm row spacing. The maize seed was a glyphosate-resistant corn hybrid. A Bt-hybrid was sowed in half of the field and a non-Bt-hybrid was sowed in the other half of the field (Whiting et al. 2014).

The Pesticide in Water Calculator (PWC) model details included the use of the runoff parameters given by the ILCornSTD scenario, and these included 28 time-varying factors, with a curve number of 87 through the growing season, which was increased to 91 after harvest. The temperature simulation was used to describe the soil layers, no irrigation was used, and to simulate continuous no-till maize post-harvest foliage was left as foliage.

Modeled insecticide concentrations using PWC

The weather station was equipped with a R.M. Young 05103 wind monitor, a Met One 385 rain gauge, a Campbell Scientific CS300 pyranometer, HMP45C temperature and relative humidity probe, Campbell Scientific CR800 data logger, and a Sierra Wireless Raven XTG cellular modem. The evaporation rate was calculated according to Linacre (1977), and the dew point temperature used in the Linacre equation was calculated according to Lawrence (2005). Negative evaporation rate values were occasionally encountered during the winter months and these values were replaced with a minimum evaporation rate value, 0.001 cm/day, to avoid condensation. Gaps in the daily field data due to station downtime were replaced with the average of two days prior and two days after the gap, with the exception of daily precipitation values, which were substituted with the precipitation record from a NOAA weather station located 4.8 km west of Edinburg, IL (US1ILCN0004).

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Table S1: Observed environmental concentrations (OEC) for tefluthrin and clothianidin in surface runoff water, ng/La

Tefluthrin / Clothianidin
2012 / 2013 / 2014 / 2012 / 2013 / 2014
38.0 ± 29.4
14.1-89.1
19-d
n = 5 / 78.4 ± 53.1
14.8-98.4
10-d
n = 6 / 10.2 ± 9.5
BRL-27.7
19-d
n = 6 / 247 ± 194
92.8-712
19-d
n = 17 / 218 ± 112
86.4-439
10-d
n = 17 / 48.7 ± 18.6
BRL-91.9
19-d
n = 14
46.5 ± 53.8
13.3-151.5
68-d
n = 6 / 23.7 ± 20.9
BRL-50.0
45-d
n = 5 / 6.98 ± 9.5
3.4-8.6
59-d
n = 6 / 119 ± 35
84.3-212
68-d
n = 18 / 215 ± 96
103-384
45-day
n = 16 / 142 ± 96
69.5-330
59-d
n = 8
13.4 ± 11.8
4.4-34.6
96-d
n = 6 / 12.4 ± 7.4
BRL-21.5
67-d
n = 6 / BRLb
all BRL
115-d
n = 6 / 86.3 ± 19.9
55.7-150.
96-d
n = 17 / 196 ± 73
73.2-324
67-d
n = 18 / 55.8 ± 19.8
27.7-92.8
115-d
n = 8
BRLb
all BRL
130-d
n = 5 / 10.3 ± 7.4
BRL-23.8
105-d
n = 6 / nac / 118 ± 33
56.2-175
130-d
n = 18 / 39.7 ± 10.2
BRL-64
105-d
n = 12 / nac

aAverage OEC ± standard deviation, range, day post-planting (post-application), and n = number of samples collected. The 2012 and 2013 OEC were from Whiting et al. (2014), and 2014 OEC were from the current project. b BRL = below reporting limit. Tefluthrin reporting limit was 3.1 ng/L, and clothianidin reporting limit was 24 ng/L, and these were calculated by multiplying the standard deviation of seven replicate samples spiked near the detection limit and the Student's t value at 99% with six degrees of freedom. cna indicates not applicable.

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Table S2: Table of acronyms used in this text

Acronym / Meaning
EEC / Estimated Environmental Concentrations
OEC / Observed Environmental Concentrations
EEC-SFP / Estimated Environmental Concentrations in a Standard Farm Pond
VVWM / Variable Volume Water Body Model
PWC / Pesticide in Water Calculator
FOCUS / FOrum for the Co-ordination and their Use
PRZM/EXAMS / Pesticide Root Zone Model/Exposure Analysis Modeling System

References

Lawrence MG (2005) A relationship between relative humidity and dewpoint temperature in moist air. Bull Am Meteorol Soc 9:225-233

Linacre ET (1977) A simple formula for estimating evaporation rates in various climates, using temperature data alone. Ag Meteorol 18(6):409-424

Whiting SA, Strain KE, Campbell LA, Young BG, Lydy MJ (2014) A multi-year field study to evaluate the environmental fate and agronomic effects of insecticide mixtures. Sci Tot Environ 497-498:534-542

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