1. Exposure of honey bees to Imidacloprid (seed treatment) Plant metabolism

Bee Safety of ImidaclopridBee Safety of Imidacloprid

Seed TreatmentSeed Treatment

to Sunflowerto Sunflower

J. Keppler, Ch. Maus, R. Schmuck, J. Keppler, Ch. Maus, R. Schmuck,

A. Nikolakis, T. SchneiderA. Nikolakis, T. Schneider

Imidacloprid Seed-Dressing Sunflower: Bee Safety 02.07.2008

1. Exposure of honey bees to Imidacloprid (seed treatment)

Plant metabolism

Residues in bee-relevant matrices


Uptake and translocation rate

The overall uptake of seed dressed

imidacloprid (incl. other soil applications)

into plants is between 1.6 and 4.9 %

The metabolism studies resulted as follows:


Systemicity Principle

As the mobility of imidacloprid in the xylem

is high, the acropetal translocation to shoots

and leaves is good (systemicity). The highest

imidacloprid concentrations in plants are

found in the oldest leaves.

The translocation of imidacloprid and its

metabolites via the phloem (basipetal

translocation) to e. g. storage organs, roots,

and fruits is low.


Discussion of bee-relevant metabolites

Bee relevant metabolites were not detected in bee-relevant matrices

(pollen and/or nectar) after seed-dressing applications of relevant

crop cultures.

Nevertheless, the bee relevant metabolites were included in the

analytical method for residue studies precautionary.


LOQ Imidacloprid: 5 ppbLOD Imidacloprid: 1.5 ppbn.d.: not detectable; < LOD

Conclusion: residues in bee-relevant matrices of sunflowers never found

Maximum residue levels of imidacloprid detected in respective plant matrices in the field

Residue levels in bee-relevant plant matrices

Sunflower Nectar

> 4 studies

Sunflower Pollen

> 4studies

Imidacloprid n.d. n.d.


Hydroxy-Imidacloprid: LOQ 5 ppb; LOD 1.5 ppbOlefine-Imidacloprid: LOQ 10 ppb; LOD 3.0 ppbn.d.: not detectable; < LOD

Conclusion: bee-relevant metabolites not detectable

Residue levels in nectar and pollen

Field residue levels of bee-relevant imidacloprid metabolites

Sunflower Nectar Sunflower Pollen

Hydroxy –Imidacloprid n.d. n.d.

Olefine-Imidaclopridn.d. n.d.


Succeeding crops – soil residues

Imidacloprid should protect seeds and plants during the growth phase, rendering the repeated use of plant protectants superfluous.

A certain degree of stability (persistence) for the a. i. in the soil is therefore necessary.

Residual amounts of imidacloprid in soil become more and more firmly attached to the soil matrix through natural binding processes.

Aged soil residues of imidacloprid are therefore less biologically available and do not pose a risk to the environment.

Numerous studies by independent experts and BCS reveal that imidacloprid is continuously degraded by microbes and is ineffective in the following agricultural cultivation period.

Bayer CropScience AG (2002): Environmental fate of imidacloprid, Pflanzenschutznachrichten Bayer, Vol. 55, Special edition)


Accumulation

Trials over several years – long term dissipation studies with

repetitive applications – confirmed that imidacloprid does not

accumulate in soil.

Bayer CropScience AG (2002): Environmental fate of imidacloprid, Pflanzenschutznachrichten Bayer, Vol. 55, Special edition)


2. Effects of Imidacloprid (seed treatment) on honey-bees

Acute effects (laboratory)

Chronic effects (laboratory)

Tunnel & field studies


Intrinsic acute bee toxicity

Imidacloprid

Regulatory LD50 (oral): 3.7 ng/bee

NOEC: 42 ppb

LD50 (contact): 42.9 ng/bee or greater


Acute sublethal effects

Lowest NOEC in reliable olfactory conditioning test: 50 ppb.

No or less pronounced effects for metabolites.

BCS conclusion:

No acute sublethal effects e. g. on learning behaviour of bees at acute dietary NOEC of 42 ppb.


Chronic lethal effects

Reliable laboratory studies showed no increased mortality after

chronic exposure to dietary concentrations of 10 ppb or lower.

However, no increased mortality was found for > 20 ppb under

more realistic exposure conditions (tunnel or field studies).


Chronic sublethal effects

No chronic mortality and no anti-feedant effects < 20 ppb

Hive development not adversely affected at concentrations < 20 ppb

No loss of foraging bees at < 100 ppb

BCS conclusion:

NOAEC under field conditions > 20 ppb


Effect threshold under field conditions

Under field conditions no adverse effects (NOAEC) at 20 ppb

No acute or chronic mortality

No adverse effects on colony strength and brood development

No losses of foraging bees due to impacts on orientation


Field-relevant NOAEC value

20 ppb is considered a field-relevant NOAEC since

No chronic mortality occurred at < 20 ppb

No anti-feedant responses occurred at < 20 ppb

Hive performance was not impaired at < 20 ppb

No loss of foraging bees was observed at < 100 ppb


Conclusion on higher tier studies

The field relevant NOAEC is > 20 ppb.


Imidacloprid residue level detected in the field in relevant matrices of sunflower:

< LOD (= 1.5 ppb)

NOAEC under field conditions: > 20 ppb

Negligible Risk to HoneybeesNegligible Risk to Honeybees

Risk assessment

Comparison of maximum exposure and NOAEC

* 1 ppb = 1 part per billion = 1 µg / kg = 0.000 000 1 %


200019991998199719961995 2001

BCS-FranceSunflower

BBA, GermanyRape

AgView, CanadaRape

Hohenheim-Germany,Phacelia

BCS-FranceSunflower

BCS-GermanyMais

BCS-GermanySunflower

BCS-GermanySummer rape

BCS-GB/SwedenSunflower

BCS-GB/SwedenSummer rape

3x3x

ACTA, FranceSunflower

3x 2x

Cultures - Sunflower - Summer rape - Winter rape - Phacelia - Maize

Various - Countries - Climates - Soils - Bee colonies - Colony sizes

No effect on bees in 18 tunnel studies

18 International tunnel studies

Bayer CropScience studies

external studies


19991998/2 2000

CONICET, ARGSunflower

Celle, GerRape

Uni Guelph, CANRape

Uni Minnes., USARape

Mayen, GerSunflower

Facanc., HungSunflower


CNEVA, FranceSunflower

Mayen, GerSunflower

BCS-GermanySunflower

BCS-FranceSunflower

1998/1199719961995

BCS-FranceSunflower



14 International field studies

Bayer CropScience studies

external studies

Cultures - Sunflower - Summer rape - Winter rape - Phacelia - Maize

Various - Countries - Climates - Soils - Bee colonies - Colony sizes

No effect on bees in 14 field studies


Thank you very much for your kind attention!

Documents

1. Exposure of honey bees to Imidacloprid (seed treatment) Plant metabolism