Glyphosate: evaluation of exposure and effects on honey bee brood (Apis mellifera)
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Transcript of Glyphosate: evaluation of exposure and effects on honey bee brood (Apis mellifera)
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
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
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