1-(allyloxy)-2-methyl-1-oxopropan-2-yl 2-chloro-5-[3-methyl-2,6-dioxo-4-(trifluoromethyl)-3,6-dihydropyrimidin-1(2H)-yl]benzoate

Toxicity to terrestrial plants

Description of key information

NOEC 0.000033 lb ai/A, EC50 0.0003 lb ai/A, EPA OPP 123-1 (Vegetative Vigor Tier II), Chetram RS (1997); supporting study
NOEC 0.0003 lb ai/A, EC50 >0.0009 lb ai/A, EPA OPP 123-1 (Seedling Emergance Tier II), Chetram RS (1997a); key study 

Additional information

A Tier 2 vegetative vigor nontarget phytotoxicity study using CGA 276854 was conducted on soybean, lettuce, radish, tomato, cucumber, cabbage, oat, ryegrass, corn, and onion. The study was performed to GLP and standardised guideline EPA OPP 123 -1 (Vegetative Vigor Tier II).

Tier 2 testing (base test) was performed in a single application at 0.00030, 0.00091, 0.0027, 0.0080, 0.024, 0.070, and 0.22 pounds of active ingredient per acre (lb ai/A). The maximum expected treatment rate is 0.22 lb ai/ A. A test continuation was performed on lettuce, radish, tomato, and cucumber at 0.0000037, 0.000011, 0.000033, 0.00010, and 0.00030 lb ai/A.

Seedlings were grown to the 1-3 true leaf stage prior to treatment. The plants were observed for 21 days following treatment. Phytotoxicity observations were recorded on days 7, 14, and 21. Percent survival, plant height, and plant dry weight effects were determined on day 21. The observed effects in the CGA 276854 treated crops and solvent treated crops were compared to the water control crops using statistical methods to determine significant differences. Observed effects were phytotoxic effects, seedling survival, plant height and plant dry weight.

Under the conditions of the test effects on growth were observed in all species. The species identified as being most sensitive according to the different effect parameters are lettuce, tomato and cucumber.

Phytotoxic effects which were noted were stunting of all ten crops, poor vigor, and death of soybean, lettuce, radish, tomato, cucumber, cabbage, and ryegrass plants at 0.22 lb ai/A. The highest treatment rate (NOEC) for the most sensitive species not significantly different from the water controls was 0.00010 lb ai/A for radish and tomato, and 0.000033 lb ai/A for cucumber.

The highest treatment rate (NOEC) not significantly different from the water controls in terms of seedling survival was 0.070 lb ai/A for oat and corn, 0.024 lb ai/A for onion, 0.0080 lb ai/A for soybean, radish. cabbage, and ryegrass, 0.00091 lb ai/A for lettuce and tomato, and 0.00030 lb ai/A for cucumber. Lowest EC25 and EC50 values are those for cucumber being 0.0011 and 0.0017 lb ai/A respectively.

The highest treatment rate (NOEC) not significantly different from water controls in terms of plant dry weight was 0.024 lb ai/A for oat, 0.0080 lb ai/A for corn and onion, 0.00091 lb ai/A for radish, cabbage, and ryegrass, and 0.00030 lb ai/A for soybean.The highest treatment rate (NOEC) for the most sensitive species not significantly different from the water control was 0.00010 lb ai/A for lettuce, tomato, and cucumber. The lowest EC25 values are 0.00024 lb ai/A for cucumber and 0.00027 lb ai/A for tomato. Lettuce did not exhibit a true dose response.The estimated EC25 value for lettuce is >0.00010 lb ai/A. The lowest EC50 values are 0.00032 lb ai/A for cucumber and an estimated >0.00030 lb ai/A for tomato and lettuce.

The highest treatment rate (NOEC) not significantly different from the water controls in terms of plant height was 0.024 lb ai/A for oat, 0.0080 lb ai/A for radish, ryegrass, corn,

and onion, 0.0027 lb ai/A for cabbage, 0.00091 lb ai/A for soybean, and 0.00030 lb ia/ A for lettuce. The highest treatment rate (NOEC) for the most sensitive species not significantly different from the control was 0.00010 lb ai/A for tomato and cucumber. Lowest EC25 and EC50 values are those for tamoto with 0.00035 and 0.00073 lb ai/A and cucumber with 0,00035 and 0,00061 lb ai/A respectively.

The study was performed according to GLP, in line with standardised guidelines, with a high standard of reporting and has thus been assigned a reliability score of 1 in line with the principles for assessing data quality set out by Klimisch (1997). The study is considered to be reliable, relevant and adequate for risk assessment purposes.However, this type of exposure i.e. deposition of the substance on the leaves and above ground portions of plants is not considered relevant for the PNEC soil derivation and therefore this study is classified as a supporting study only.

 

In addition a Tier 2 seedling emergence nontarget phytotoxicity study using CGA 276854 was conducted on soybean, lettuce, radish, tomato, cucumber, cabbage, oat, ryegrass, corn, and onion. The study was performed to GLP and standardised guideline EPA OPP 123 -1 (Seedling Emergence Tier II).

Tier 2 testing (base test) was performed in a single application at 0.0027, 0.0080, 0.024, 0.070, and 0.22 pounds of active ingredient per acre (lb ai/A). The maximum expected treatment rate is 0.22 lb ai/ A. A test continuation was necessary to determine the NOEC for some or all of the criteria for lettuce, radish, tomato, and cabbage with application rates of 0.000033, 0.00010, 0.00030, 0.00090, and 0.0027 lb ai/A.

The plants were observed for 21 days following treatment. Emergence was recorded on days 10 and 14 and survival on day 21. Visual phytotoxicity observations were recorded on days 10, 14, and 21. Plant height and dry weight effects were determined on day 21. The observed effects in the treated test species were compared to the water control using statistical methods to determine significant differences.

Under the conditions of the test effects were observed in all species. The species identified as being most sensitive according to the different effect parameters are lettuce, tomato and cabbage (all concentrations are representative of the active ingredient and corrected for sample purity).

Phytotoxic effects which were noted were stunting, poor vigor, and death of plants. The highest treatment rate (NOEC) for the most sensitive species not significantly different from the water controls was 0.00030 lb ai/A for lettuce and tomato.

The highest treatment rate (NOEC) not significantly different from the water controls in terms of seedling emergence was as 0.070 lb ai/A for oat, 0.024 lb ai/A for soybean and ryegrass and 0. 0080 I b ai/A for onion. Due to the high mortality rate of cucumber seedlings at 0.070 and 0.22 lb ai/A the NOEC was determined to be 0.024 lb ai/A. The NOEC for radish and cabbage were determined to be 0.0080 lb ai/A and 0.0027 lb ai/A respectively due to seedling deaths at the higher treatment rates at 10 and 14 days after treatment. The highest treatment rate (NOEC) not significantly different from the water controls was 0.00090 lb ail A for lettuce and tomato. Lowest EC25 and EC50 values are those for lettuce being >0.0009 and >0.0027 lb ai/A and tomato being >0.0027 and >0.0027 lb ai/A respectively.

The highest treatment rate (NOEC) not significantly different from the water controls in terms of seedling survival was as 0.070 lb ai/A for oat, 0.024 lb ai/A for soybean, ryegrass and corn, 0.0080 lb ai/A for cucumber, 0.0027 lb ai/A for radish and onion, 0.0009 lb ai/A for cabbage and 0.0003 lb ai/A for lettuce and tomato. Lowest EC25 and EC50 values are those for lettuce and tomato being >0.0009 and >0.0009 lb ai/A respectively.

The highest treatment rate (NOEC) not significantly different from water controls in terms of plant dry weight was 0.0080 1bai/A for soybean, oat and ryegrass, 0.0027 1b ail A for cucumber, corn and onion, 0.00090 lb ai/A for lettuce, radish and cabbage and 0.00030 lb ai/A for tomato. The lowest (estimated) EC25 and EC50 values are >0.00030 lb ai/A and >0.00090 lb ai/A for tomato.

The highest treatment rate (NOEC) not significantly different from the water controls in terms of plant height was 0.0080 1b ai/A for oat, 0.0027lb ai/A for soybean, cucumber, cabbage, ryegrass, corn and onion, 0.00090 lb ai/A for lettuce and radish and 0.00030 lb ai/A for tomato. Lowest EC25 and EC50 values are those for tomato with 0.0011 and 0.0019 lb ai/A.

The study was performed according to GLP, in line with standardised guidelines, with a high standard of reporting and has thus been assigned a reliability score of 1 in line with the principles for assessing data quality set out by Klimisch (1997). The study is considered to be reliable, relevant and adequate for risk assessment purposes.

 

The available data are considered to be complete and the following conclusions for toxicity have been taken forward for risk assessment based on the worst case scenario using the most sensitive data; NOEC 0.0003 lb ai/A and EC₅₀ >0.0009 lb ai/A (all concentrations are representative of the active ingredient and corrected for sample purity).