EPA Data Call-In Discussion 

Concerning Exposure and Toxicity 

of Clothianidin to Bees

September 23, 2013

Richard Allen

Dan Dyer

David Fischer

Allen Olmsted

Sue Shen
Addressing EPA’s questions following our presentations in 

May and submission of protocols in August - EXPOSURE

• What do Valent/Bayer propose EPA use as exposure values when 

crop specific data are unavailable?

• What do Valent/Bayer propose EPA use as exposure values when 

application methods at different use sites differ from the available 

studies’ application methods?

• What confidence do Valent/Bayer have that proposed crops will be 

inclusive of the range of clothianidin residues expected from 

currently registered uses?

• What do Valent/Bayer propose as an approach to ensure that 

residues in tomato and other fruiting vegetables are protectively 

represented? 2
Objective of Tier II exposure studies: Refine the upper bound 

residue levels in pollen and nectar, with measurements under 

actual use conditions to support pollinator risk assessments

• Seed treatment

• Soil applications

• Foliar applications to annual crops

• Applications to perennial crops

Use Patterns

• Crops that receive pollination services

• Crops that are attractive to bees*

• Major crops

• Major clothianidin uses

Relevance 

• Pollen and nectar collection

• Extent of crop acreage

• Surrogates for crops of similar morphology, application 

timings and rates

• Label mitigation as an alternative to data generation

Practicality

3

EPA White paper:

“Tier II exposure assessments rely upon 

field measurements of the assessed 

pesticide in pollen and nectar of crops that 

are relevant to the use of the pesticide and 

the exposure of bees (e.g., crops that

are attractive to bees).”
Seed Treatments

Use patterns (mg/seed)

• Corn: 1.25

• Canola: 0.016

• Soybeans: 0.13

• Cotton: 0.42

• Sugar beet: 0.6

• Potato: 12.5 g/100 kg 

seed

• Vegetables: 0.07 – 1.19

Relevance

• Major use

• Major use; pollination 

services for hybrid seed

• Major use

• Attractiveness varies by 

region

• Not relevant for ag

production

• Not attractive

• Minor use/ pollination 

services used for seed 

production

Practicality

• Studies ongoing. 

Highest use rate

• Studies ongoing. 

Surrogate for brassicae

• Studies ongoing

• Indeterminate flowering 

– sampling challenge

•

•

• Canola as surrogate for 

brassicae. Label 

mitigation for seed 

production possible

4
Soil Application to annual crops

Use patterns 

(g/ha)

• Cucurbits @ planting: 224

• Fruiting Vegetables

@ planting: 224

• Leafy Vegetables 

@ planting : 224

• Root and tuber vegetables @ 

planting: 224

• Brassica Vegetables @ 

planting: 224

Relevance

• Pollination services

• Some use pollination services. 

Not a source of nectar

•Ag production not relevant for 

bees

•Ag production not relevant for 

bees

•Ag production not relevant for 

bees 

Practicality

• Sampling challenge except 

pumpkins. Study ongoing.

• Sampling challenge 

(bumblebees or toothbrush)

• Label mitigation possible for 

seed production

• Label mitigation possible for 

seed production

• Label mitigation possible for 

seed production

5
Foliar Application to Annual Crops 

Use patterns (g/ha)

• Cotton: 2 x 112

• Cucurbits: 2 x 112

• Fruiting Vegetables: 2 x 112

• Leafy Vegetables: 2 x 112

• Root and tuber vegetables: 4 x 56

• Brassica: 2 x 112

• Rice 1 x 84

• Soybean: 2 x 112

• Tobacco: 3 x 75

Relevance

• Attractiveness varies by region. 

Major use

• Requires pollination services

• Some use services but no apps 

during flowering

• Ag production not relevant for bees

• Ag production not relevant for bees

• Ag production not relevant for bees

• Not relevant for bees

•

• Not relevant for bees

Practicality

• Study ongoing

• Study ongoing

• Sampling challenge (bumblebees or 

toothbrush)

• Label mitigation possible for seed 

production

• Label mitigation possible for seed 

production

• Label mitigation possible for seed 

production

•

• Label mitigation possible for postbloom use only

•

6
Soil & Post Bloom Foliar Application to 

Perennial Crops 

Use patterns 

(g/ha)

• Tree nuts (post bloom 

foliar): 2 x 112

• Pome fruits (post bloom 

foliar): 1 x 224

• Peach (post bloom foliar): 

2 x 112

• Cranberry (post bloom, 

soil): 224

• Grapes (up to harvest): 

224

Relevance

• Almonds require 

pollination services

• Pollination services 

provided in some areas

• Pollination services 

provided in some area

• Pollinated by bumble 

bees but post-bloom use

• Not relevant for bees; use 

pattern targeted at late 

season pests

Practicality

• Study proposed

• Study proposed

• Study proposed

• Label mitigation in place 

(post-bloom only)

•

7
Cucurbit protocols as surrogate for fruiting 

vegetables

Parameters Cucurbits Fruiting vegetable

Use Patterns Ongoing protocols:

Soil: 1 x 224 g/ha at planting

Soil: 1 x 224 g/ha to soil at BBCH 

21 -23

Foliar: 2 x 105 g/ha at BBCH 21-23 

and 51 (before bloom)

Soil: 1 x 224 g/ha at planting

Foliar: 4 x 56 or 3 x 75 g/ha 

(before bloom)

Water demand CA: About 6-7 inches between 

planting and flowering

CA: About 6-7 inches between 

planting and flowering

Comparison of data for 

imidacloprid

Bee collected nectar 1 – 8 ppb

Bee collected pollen < 10 – 32 

ppb

Hand collected anthers: 14 –

54 ppb

8

Anthers vs pollen & nectar

Hand collection vs bee collection

Different fields and application rates
Addressing EPA’s questions following our presentations in 

May and submission of protocols in August - EFFECTS

• Have Valent/Bayer considered conducting semi-field tunnel studies 

and/or feeding studies that develop colony level dose-response 

relationships that can be compared to the residue data being 

generated?

– Aware of proposal from other registrants; Many studies have 

already been conducted by BCS. Plan to evaluate all existing 

data (lab and field) to determine if additional studies are needed 

to further inform the risk assessment. 

• How does Valent/Bayer suggest using currently available data as 

well as additional data to be generated to be protective of non-Apis

bees?

– ‘ A reasonable surrogate’ (SAP Panel response). Further testing 

should be held in reserve pending development of test methods 

and risk assessment scenarios for non-Apis species. 9
Summary of Program

• Completed and ongoing seed treatment studies allow for an upper 

bound exposure relevant for all seed treatment uses

• Data for soil treatments and foliar treatments are representative and 

focused on major crops, relevant for bees. Other crops not relevant 

because they either:

– do not flower in agricultural production

– not attractive to bees

– applications are made post-blooms 

• We consider the range of use patterns covered by these studies 

allow definition of an upper-bound exposure level for a specific crop 

group (e.g. investigating foliar and soil applications to cucurbits) 

10
Back Up Slides

11
Accumulation and Bioavailability in Corn / Canola

• 2012 – 20 corn sites (US); 5 

canola sites (Canada)

• Corn pollen; canola pollen and 

nectar -- hand collected

• Soil cores (0-12 inch); 

composite of 8 cores

• Corn pollen samples limited 

due to drought

• No accumulation of residues 

in soil from multiple years of 

use (see graph)

• Pollen/nectar residues low, 

and not correlated with years 

of use (e.g. 1.1 ppb from site 

with 9 years of use)

12

2013: additional 30 corn and 10 

canola sites – samples collected
Imidacloprid – tomato vs melon

• Tomato

– 2 x 0.125 lb a.i./acre; drip chemigation

– App. 1: closely following transplanting; App 2: 52-57 days 

following App. 1

– 0.18 to 0.38 lb ai/A applied in previous year

– Anthers and leaves sampled

• Melon

– 0.23-0.38 (typically 0.30) lb a.i./acre; soil application at transplant

– Bee collected pollen and nectar (tented bees); and leaves

13
Imidacloprid – tomato vs melon

14

Tomato

CommodityPlot

T

ype a

Total Imidacloprid Residue Levels (ppm) d

nMin

Max

HighestAverageSite Residue

Median

MeanStandardDeviation

Tomato – Anthers Heavy

Soil 8 0.014 0.030 0.027 0.022 0.021 0.005

Tomato – Anthers Medium

Soil 10 0.016 0.054 0.046 0.036 0.034 0.012

Tomato – Leaves Heavy

Soil 8 0.057 0.14 0.12 0.089 0.093 0.026

Tomato - Leaves

Medium

Soil 10 0.038 0.23 0.20 0.10 0.11 0.061

Melon