Glyphosate: evaluation of exposure and effects on honey bee brood

(Apis mellifera) Georg von Mérey, Steve Levine, Janine Doering, Steven

M. Norman, Philip Manson, Peter Sutton, Helen Thompson

On behalf of the Glyphosate Task Force

Glyphosate

Broad spectrum herbicide with plant-specific MoA inhibiting amino acid production

Formulated as salts, which are more soluble in water than glyphosate acid. Glyphosate

IPA – Potassium (K) –

Ammonium (NH4) – Dimethyl Ammonium (DMA) –

Shikimic acid

Shikimic acid-3-phosphate

5-enolpyruvyl shikimic acid-3-

phosphate

Chorismic acid

Gylphosate

Anthranilic acid

Phenylalanine Tyrosine Tryptophan

EPSP synthase

Glyphosate Dissipation Insect and plant material

0 10 20 30 400

2

4

6

8Insect Residue Decline

Half Life 6.025

Time (days)

Resid

ue m

g a

.e./

kg

0 10 20 30 400

20

40

60

80

100Grass Residue Decline

Half Life = 2.799

Time (days)

Bee risk assessment

• EU Dir 91/414:

– Acute oral LD50 [ug a.i./bee]

– Acute contact LD50 [ug a.i./bee]

– HQ = App. Rate [g a.i./ha] / LD50 ≤ 50

• EU Reg No 1107/2009

– Acute oral+contact LD50

– Chronic adult

– Bee development, etc.

OECD 213 (1998)

OECD 214 (1998)

OECD 213+214 (1998)

Decourtye et al. 2010

OECD 75, Aupinel et al. (2009)

Exposure Scenarios

• Acute

• Development + Chronic

≈ Application rate

Depends on residues in

relevant matrices

Bee risk assessment (2)

• Acute oral/contact dosage typically 100 ug a.i./bee - > App. Rate ≤ 5 kg a.s. ha, covers most active substances (except insecticides…)

• Dose setting for chronic exposure

• 100 ug a.s./bee not necessarily useful / achieveable / representative?

Test design

• Residue-based doses in an « Oomen » setup 1. Residue trial to measure

maximum theoretical exposure (max rate, on flowering plants in greenhouse)

2. Brood test, using Oomen method with sucrose solution spiked with relevant concentration of test item derived from (1)

Residues in pollen, nectar, larvae

Thompson et al., 2014. IEAM in press

0

5

10

15

20

74DAT

Gly

ph

osa

te R

es

idu

e (

mg

a.e

./kg

)

larvae

Two Approaches to Assess Exposure

1. Generic data: Based on published data by Rortais et al. 2005 on the requirements for nectar and pollen by larvae

2. Study data: Based on the observations and measurements made in the exposure study for pollen and nectar collection

• As a worst-case example considering colony size used in the exposure study, the colony collected 6 g pollen and 1296 mL nectar

• Of this the brood consumes 4.5 g pollen and 135 g nectar (Rortais et al. 2005) which allowed the excess to be stored for later consumption

Experimental Design for Brood Study

• Colonies were placed in 5 groups of 4 colonies and placed at >20 m apart

• Colonies had dead bee traps to count dead bees.

• Brood cells were marked before dosing using the standard Oomen acetate overlay sheet method

• 100 brood cells containing eggs, 100 cells containing 1-2 day old larvae and 100 cells containing 3-4 day old larvae were selected in each colony

Dunnington, Yorkshire, UK, field site

Field Site

Larval Assessment

Survival of eggs – young – old larvae

# no young larvae survived the positive control treatment (fenoxycarb)

Colony Development

• Varroa infestations in the colonies were low and did not significantly impact the results of the study

• Evaluated 4 parameters: – No treatment effect on number of bees

– No treatment effect on level of brood

– No treatment effect on sealed brood

– No treatment effect by levels of unsealed brood

Treatment groups: 300 mg/L, 150 mg/L, 75 mg/L

Discussion

Thompson, 2013

Burgett & Fisher, 1990

Ferguson, 1987

Australia

NOER = n.a.

NOEC = 5 mg a.e./L

Belize

NOER = 4 kg a.e./ha

NOEC = 18 000 mg a.e./L

UK

NOER= 4.3 kg a.e./ha

NOEC = 300 mg a.e./L

Source: www.mapresources.com

Conclusions

• Large weight of evidence that glyphosate is not acutely toxic to bees

• Exposure study demonstrate and quantify exposure to larvae.

• Residues decline rapidly in pollen, nectar and larvae

• Brood study demonstrates that glyphosate does not impact adult bees or bee brood development under worst case exposure scenarios

Thank you for your attention