2-amino-6-methyl-4-propyl-1,2,4-triazolo[1,5-a]pyrimidin-5(4H)-one

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP, available as unpublished report, minor restrictions in design and/or reporting but otherwise adequate for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance was applied at 30 g active ingredient per ha to 6 m x 6 m plots permanent grassland in spring 1977, 1978, and 1979. Earth worms were sampled from untreated control, toxic standard and treated plots 2 months before and 1, 6, and 12 months after the first treatment and 12 months after the second and third treatments.

GLP compliance:

no

Analytical monitoring:

no

Details on preparation and application of test substrate:

The material used was a 1250 mg/L aqueous formulation applied at a rate of 30 g ai ha- 1 on 20 April 77, 25 April 78 and 24 April 79. The rate calculation was based on the nominal test substance concentration. The formulations used in 1978 and 1979 actually contained 0.141% w/w test substance (analysis ref. FAJ 0870) and 0.126% w/w test substance (analysis ref. FAJ 2488) respectively. No analysis was available for the formulation used in 1977.
The test substance was applied to plot number 7 in each block. Plots 23 and 24 were used as untreated controls. Benomyl was applied to plot 8 annually at a rate of 5.0 kg ai ha- 1 on the same days as the test substance.
Application in 1977 was by a 1 m dribble bar, with 104, 0.8 mm diameter holes along its length, attached to a backpack containing the chemical in 9 litres of water. This was applied by making 6 passes over a plot in one direction (each pass being adjacent to the previous one) and 6 passes in a direction at right angles to the first 6 to ensure even coverage. Applications in 1978 and 1979 were by a 6 m hand-held boom sprayer pressurized by CO2 through 11'Teejet 11008' jets, 50 cm apart and 28 cm from the ground. Tank pressures were 40 psi (276 kPa), and line (spraying) pressures 20 psi (138 kPa). Each treatment plot was sprayed with the chemical in 9 litres of water. Two 15-second passes were made with the sprayer per plot, the second pass at right-angles to the first to ensure even coverage.

Test organisms (species):

other: Allolobophora chlorotica, Lumbricus terrestris, Lumbricus festivus

Animal group:

annelids

Details on test organisms:

TEST ORGANISM:
- Common name: Earthworm
- Identification: The identification key used was that published by the Linnean Society of London: Synopses of the British Fauna Series, No. 6: Lumbricidae by B M Gerard.

Study type:

semi-field study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

156 wk

Remarks:

3 annual spring applications, over a 3 year period from sping 1977 to spring 1980

pH:

7.1

Details on test conditions:

LOCATION AND HISTORY OF TRIAL SITE:
The trial site was located at ecology section’s small plots “nuptown” site on “18 acres” field, Jealott’s Hill Farm, Berkshire. Ordnance survey map reference SU 889735. Since the foundation of the site in the spring of 1975 none of the plots used for this trial have had any application of experimental pesticide. Prior to 1975 the history was as follows: 1973 and 1974: grass. Autumn 1974 : winter wheat. The soil texture on “Nuptown” is a sandy loam.

LAYOUT AND MANAGEMENT OF THE PLOTS:
The trial site is arranged as 3 blocks of 6 m x 6 m plots. All plots are surroundedn by a 1.5 m guard strip and are randomly numbered within each block. A short grass sward was maintained on the plots by periodic mowing. Grass cuttings were left on the surface.

SOIL PROPERTIES::
The soil is a sandy loam containing:
- Coarse sand (particle size 200 – 2000 µm) 37%
- Fine sand (particle size 20 – 200 µm) 28%
- Silt (particle size 2 – 20 µm) 16%
- Clay (particle size <2 µm) 19%

- Particle size analysis: Coarse sand fraction is removed by wet sieving; fine sand by sedimentation/washing; silt and clay by sequential sedimentation and analysis of supernatant (using stokes law of particle sedimentation).
- pH analysis: By agitation for 30 minutes with deionized water (1:2.5 soil: water slurry) and determination by glass electrode.
- Organic matter 3.8%. as determined by using potassium dichromate/concentrated H2SO4 to oxidise the organic matter, followed by titration of excess dichromate with ferrous sulphate (walkley-black method)
- Cation Exchange Capacity 14.7 meq./100g soil as determined by sodium saturation at pH 7.0 and flame spectrophotometry.

Nominal and measured concentrations:

nominal: 30 g active ingredient per ha

Reference substance (positive control):

yes

Remarks:

Benomyl

Duration:

265 d

Dose descriptor:

NOEC

Effect conc.:

30 g/ha

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: total numbers of earthworms

Remarks on result:

other: The test substance applied at 30 g active ingredient per ha had no significant effect on total numbers, total weights, and numbers of individual species of earthworms.

Details on results:

The test substance was applied at 30 g active ingredient per ha had no significant effect on total numbers, total weights, and numbers of individual species of earthworms.

The only significant decreases were in immature Allolobophora chlorotica (P=1%) 1 and 12 months after the first treatment. However, pretreatment numbers of immature A. chlorotica were low (P=5%) and this may have been partly responsible for these apparent significant reductions. Twelve months after the second and third treatments number of immature A. chlorotica were not significantly different from controls (P=5%). Number of adult Lumbricus terrestris were low one month after the first treatment and twelve months after the third treatment (P=5%). On all other sampling ocassions numbers were very similar to those on control plots.

Results with reference substance (positive control):

Benomyl reduced the weight and numbers of many species of earthworms. The population of L. festivus was much greater one year after treatment than on the controls (P = 1%). One explanation for this is that the cocoons produced in spring prior to treatment are resistant to the effects of benomyl, and on hatching, survive better on benomyl plots than on untreated controls, because of reduced competition with other species. Thus, in subsequent springs it would be expected that more L. festivus on benomyl plots would lay cocoons.

Validity criteria fulfilled:

not applicable

Conclusions:

The test substance applied at a rate of 30 g active ingredient per ha, which is 10x the rate applied in maximum normal ‘gramoxone’ use, will not have any adverse effects on earthworm populations.

Executive summary:

The test substance was applied at 30 g active ingredient per ha to 6 m x 6 m plots permanent grassland in spring 1977, 1978, and 1979. Earth worms were sampled from untreated control, toxic standard and treated plots 2 months before and 1, 6, and 12 months after the first treatment and 12 months after the second and third treatments. The test substance at this application rate had no significant effect on total numbers, total weights, and numbers of individual species of earthworms. The only significant decreases were in immature Allolobophora chlorotica (P=1%) 1 and 12 months after the first treatment. However, pretreatment numbers of immature A. chlorotica were low (P=5%) and this may have been partly responsible for these apparent significant reductions. Twelve months after the second and third treatments number of immature A. chlorotica were not significantly different from controls (P=5%). Number of adult Lumbricus terrestris were low one month after the first treatment and twelve months after the third treatment (P=5%). On all other sampling ocassions numbers were very similar to those on control plot. The test substance applied at a rate of 30 g active ingredient per ha, which is 10x the rate applied in maximum normal ‘gramoxone’ use, will not have any adverse effects on earthworm populations.

Description of key information

The 265-d NOEC is 30 g (active ingredient) per ha.

Additional information

The test substance was applied at 30 g active ingredient per ha to 6 m x 6 m plots permanent grassland in spring 1977, 1978, and 1979. Earthworms were sampled from untreated control, toxic standard and treated plots 2 months before and 1, 6, and 12 months after the first treatment and 12 months after the second and third treatments. The test substance applied at 30 g active ingredient per ha had no significant effect on total numbers, total weights, and numbers of individual species of earthworms. The only significant decreases were in immature Allolobophora chlorotica (P=1%) 1 and 12 months after the first treatment. However, pre-treatment numbers of immature A. chlorotica were low (P=5%) and this may have been partly responsible for these apparent significant reductions. Twelve months after the second and third treatments the numbers of immature A. chlorotica were not significantly different from controls (P=5%). Number of adult Lumbricus terrestris were low one month after the first treatment and twelve months after the third treatment (P=5%). On all other sampling occasions numbers were very similar to those on control plot. The test substance applied at a rate of 30 g active ingredient per ha, which is 10x the rate applied in maximum normal ‘gramoxone’ use, will not have any adverse effects on earthworm populations.