imidacloprid (ISO); 1-(6-chloropyridin-3-ylmethyl)-N-nitroimidazolidin-2-ylidenamine

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06 Apr to 04 May 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)

Version / remarks:

2006

Deviations:

yes

Remarks:

According to OECD 208: slight deviation of humidity without any impact

GLP compliance:

yes (incl. QA statement)

Remarks:

THE DEPARTMENT OF HEALTH OF THE GOVERNMENT OF THE UNITED KINGDOM, delivered on 12 Jan, 2015

Analytical monitoring:

yes

Details on sampling:

no information
The measured level of imidacloprid verified the concentration in the spray solution was 102.0 % of the expected nominal concentration.

Vehicle:

no

Details on preparation and application of test substrate:

The test material spray solution was prepared for a single treatment at 100 g a.s./ha in deionised water, (1.45 g test material/L in 500 mL of deionised water). The treatments were applied to the plants aerial growth using a Track Sprayer at a spray pressure of 2 bar, fitted with a Lurmark 02 F110 nozzle. The sprayer was calibrated prior to the application of the treatments. An application volume equivalent to 201 L/ha was achieved using a speed of 2.75 m/s at a target distance of 50 cm above the spray area i.e. the top of the plant pots. The control sets were treated with deionised water in two sessions followed by the test item treatment group sets.

Species:

Lycopersicon esculentum

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family:Solanaceae
Supplier: Jungle Seeds, Watlington,UK

Species:

Helianthus annuus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Asteraceae (Compositae)
Supplier: Syngenta Seeds Ltd, Cambridge, UK

Species:

Beta vulgaris

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Famiy: Chenopodiaceae
Supplier: Syngenta Seeds Ltd, Cambridge,UK

Species:

Glycine max (G. soja)

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Fabaceae (Leguminosae)
Supplier: Soya (UK) Ltd., Southampton, UK

Species:

Brassica napus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Brassicaceae (Cruciferae)
Supplier: Harlow Agricultural Merchants, Harlow,UK

Species:

Cucumis sativus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Cucurbitaceae
Supplier: Moles Seeds (UK) Ltd, Colchester, UK.

Species:

Lolium perenne

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family: Poaceae (Gramineae)
Supplier: Herbiseed, Twyford, UK.

Species:

Allium cepa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family: Liliaceae (Amaryllidaceae)
Supplier: Marshalls Seeds Ltd, Alconbury Hill, UK

Species:

Avena sativa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family: Poaceae (Gramineae)
Supplier: Frontier Agriculture, Thatcham,UK

Species:

Zea mays

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family: Poaceae (Gramineae)
Supplier: Herbiseed, Twyford, UK

Test type:

seedling emergence and seedling growth test

Study type:

extended laboratory study

Substrate type:

natural soil

Limit test:

yes

Total exposure duration:

21 d

Remarks:

after 50% emergence

Test temperature:

12.6 – 30.6°C

pH:

6.8

Moisture:

Soil: 12.6%
Humidity: 18.9– 70.5%

Details on test conditions:

The temperature, humidity and light intensity throughout the study were monitored. The temperature and humidity ranges are presented above. Glasshouse lighting was set to achieve a 16: 8 hour light: dark cycle for the duration of the study (intensity: 0.4-86.3 K lux). The humidity in the glasshouse, on several occasions, during the course of the growth period fell below the 70±25 % quoted for environmental conditions that are generally recommended for greenhouse testing but this was not considered to have any influence on the emergence and growth of the plants as the control plants showed no physiological problems.

The seeds were sown in soil that conformed to the characteristics specified in OECD Guideline 208. The soil used in the study was a commercially available loamy sand (USDA Classification) supplied by Baileys of Norfolk, Brick Kiln Road, Hevingham, Norfolk NR10 5NL, UK.

At least five replicate pots per treatment were sown ensuring that 20 plants were achieved per treatment group.

All plant pots were assessed for emergence, visual injury/phytotoxicity, survival and the BBCH growth stage at 7, 14 and 21 days after 50 % emergence in the control for each species.

Nominal and measured concentrations:

Nominal: Imidacloprid SL 200 g/L (100 g a.s./ha) equivalent to 0.133 mg a.s./kg soil dw

Reference substance (positive control):

not specified

Key result

Species:

other: all tested species

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 100 g/ha

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

seedling emergence

Key result

Species:

other: all tested species

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 0.133 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

seedling emergence

Details on results:

Spray application was performed so the result is equivalent to EC50 > 0.133 mg a.s./kg dry weight soil.
The soil surface application of the test material at a rate of 100 g a.s./ha to ten terrestrial non-target plant species did not produce effects on the emergence, survival and shoot dry weight of the plants reaching or exceeding the 50 % threshold for further testing.
The endpoint determinations of emergence, survival and shoot dry weight for all plant species treated with the test item were not statistically significantly different compared to the control data with the exception of tomato (Solanum lycopersicon) where there was 25 % inhibition of emergence and oilseed rape (Brassica napus) where there was a 24.3 % inhibition of dry shoot weight compared to the control data.

Please refer to "overall remark/ attached background material" field for result tables.

Table 1: Validity criteria for OECD 208

Criterion	Outcome	Criterion fulfilled
Seedling emergence in the controls is ≥ 70%.	Between 85 and 100%	Yes
No visible phytotoxic effects (e.g. chlorosis, necrosis, wilting, deformatons) in control seedlings and the plants of every particular species exhibit normal variation in growth and morphology.	No phytotoxic effect	Yes
In the controls, the mean survival of emerged control seedlings is ≥ 90% for the duration of the study.	100% of survival	Yes
The environmental conditions for a particular species are identical and the growing media contain the same amount of soil matrix, support media or substrate from the same source.	Identical conditions	Yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the overall EC50 (21 d) was > 100 g a.s./ha equivalent to 0.133 mg a.s./kg dws.

Reference 2

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 Apr to 25 Apr, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 227 (Terrestrial Plant Test: Vegetative Vigour Test)

Version / remarks:

2006

Deviations:

yes

Remarks:

According to OECD 227: slight deviation of humidity without influence

GLP compliance:

yes (incl. QA statement)

Remarks:

THE DEPARTMENT OF HEALTH OF THE GOVERNMENT OF THE UNITED KINGDOM, delivered on 12 January 2015

Analytical monitoring:

yes

Details on sampling:

no information
The measured level of imidacloprid verified the concentration in the spray solution was 98.0% of the expected nominal concentration.

Vehicle:

no

Details on preparation and application of test substrate:

The test material spray solution was prepared for a single treatment at 100 g a.s./ha in deionised water, (1.45 g imidacloprid SL 200 g/L in 500 mL of deionised water). The treatments were applied to the plants aerial growth using a Track Sprayer at a spray pressure of 2 bar, fitted with a Lurmark 02 F110 nozzle. The sprayer was calibrated prior to the application of the treatments. An application volume equivalent to 201 L/ha was achieved using a speed of 2.8 m/s at a target distance of 50 cm above the spray area i.e. the top of the leaves. The plants in both the control and the treatment group were split into two sets. The control sets were treated with deionised water in two sessions followed by the test item treatment group sets.

Species:

Lycopersicon esculentum

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Solanaceae
Supplier: Jungle Seeds, Watlington,UK

Species:

Helianthus annuus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Familiy: Asteraceae (Compositae)
Supplier: Syngenta Seeds Ltd, Cambridge,UK.

Species:

Beta vulgaris

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Chenopodiaceae
Supplier: Syngenta Seeds Ltd, Cambridge,UK.

Species:

Glycine max (G. soja)

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Fabaceae (Leguminosae)
Supplier: Soya (UK) Ltd., Southampton, UK.

Species:

Brassica napus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Brassicaceae (Cruciferae)
Supplier: Harlow Agricultural Merchants, Harlow,UK

Species:

Cucumis sativus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

Family: Cucurbitaceae
Supplier: Moles Seeds (UK) Ltd, Colchester, UK.

Species:

Lolium perenne

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family Poaceae (Gramineae)
Supplier: Herbiseed, Twyford, UK.

Species:

Allium cepa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family: Liliaceae (Amaryllidaceae)
Supplier: Marshalls Seeds Ltd, Alconbury Hill,UK

Species:

Zea mays

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family Poaceae (Gramineae)
Supplier: Herbiseed, Twyford, UK.

Species:

Avena sativa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

Family Poaceae (Gramineae)
Supplier: Frontier Agriculture, Thatcham,UK

Test type:

vegetative vigour test

Study type:

extended laboratory study

Substrate type:

natural soil

Limit test:

yes

Total exposure duration:

21 d

Remarks:

young plants at the 2 to 4 true leaf growth stage

Test temperature:

14.8 – 30.3°C

pH:

7.8

Moisture:

Soil: 10.3% w/w
Greenhouse humidity: 20.5 – 70.5%

Details on test conditions:

The temperature, humidity and light intensity throughout the study were monitored. The temperature and humidity ranges are presented above. Glasshouse lighting was set to achieve a 16: 8 hour light: dark cycle for the duration of the study (intensity: 0.4-82.3 K lux). The humidity in the glasshouse, on several occasions, during the course of the growth period fell below the 70±25 % quoted for environmental conditions that are generally recommended for greenhouse testing but this was not considered to have any influence on the emergence and growth of the plants as the control plants showed no physiological problems.

All plants were assessed for visual injury/phytotoxicity, survival and the BBCH growth stage at 7, 14 and 21 days after treatment.

The number of seeds per pot was 4 for monocotyledonae in each of the 5 replicates, except for maize. The number of seedes per pot was 2 for dicotyledonae and maize in each of the 10 replicates.

Nominal and measured concentrations:

Nominal: Imidacloprid SL 200 g/L (100 g a.s./ha) equivalent to 0.133 mg a.s./kg dry soil.

Reference substance (positive control):

not specified

Key result

Species:

other: for all tested species

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 100 g/ha

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: survival and shoot dry weight

Key result

Species:

other: for all tested species

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 0.133 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: surival and shoot dry weight

Details on results:

Spray application was performed so the result is equivalent to EC50 > 0.133 mg a.s./kg dry weight soil.
The foliar application of the test material at a rate of 100 g a.s./ha to ten terrestrial non-target plant species did not produce effects on the survival and shoot dry weight of the plants reaching or exceeding the 50% threshold for further testing. The endpoint determinations of survival and shoot dry weight for all plant species treated with the test item were not statistically significantly different compared to the control data.

Please refer to "overall remark/ attached background material" field for result tables.

Table 1. Validity criteria for OECD 227

Performance criteria	Outcome	Criterion fulfilled
Seedling emergence is ≥ 70%.	At least 70%	Yes
In the controls, the plants do not exhibit phytotoxic effects (e.g. chlorosis, necrosis, wilting, leaf and stem deformations) and only normal variation in growth and morphology for that particular species.	No phytotoxic effect	Yes
In the controls, the mean plant survival is ≥ 90% for the duration of the study.	100% of survival	Yes
The environmental conditions for a particular species are identical and growing media contain the same amount of soil matrix, support media, or substrate from the same source.	Identical conditions	Yes

 

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the overall EC50 (21 d) was > 100 g a.s./ha equivalent to 0.133 mg a.s./kg dws.

Description of key information

The overall EC50 (21 d) was > 100 g a.s./ha equivalent to 0.133 mg a.s./kg dws for seedling emergence and vegetative vigour studies.

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:

0.133 mg/kg soil dw

Additional information

In the first key study (2016), the toxicity of test material sprayed to terrestrial plants was investigated in a 21-day test on vegetative vigour according to guideline OECD 227. Ten species (4 monocotyledonous and 6 dicotyledonous) were exposed to nominal concentration of 100 g a.s./ha (equivalent to 0.133 mg a.s./kg dry soil), alongside with a control. No effect exceeding 50% or no significant adverse effects were observed after 21 days exposure for survival and shoot dry weight.

 

In the second key study (2016), the toxicity of test material sprayed to terrestrial plants was investigated in a 21-day test on seedling emergence according to guideline OECD 208. Ten species (4 monocotyledonous and 6 dicotyledonous) were exposed to nominal concentration of 100 g a.s./ha (equivalent to 0.133 mg a.s./kg dry soil), alongside with a control. Significant adverse effects lower than 25% were only observed after 21 days exposure for emergence in tomato and shoot dry weight in oilseed rape.

Both key studies resulted in EC₅₀ > 0.133 mg a.s./kg dws.

Long-term toxicity testing is not deemed necessary considering the lack of effects in short-term toxicity studies with plants over 21 days.

There are three additional supportive studies (conducted with OECD guidelines) with standard species. The one with incorporated test item on three species resulted in EC₅₀ > 100 mg a.s./kg dws. The two sprayed test item resulted in EC₅₀ > 0.747 mg a.s./kg dws.