Studies on dissipation of thiamethoxam insecticide in two different soils and its residue in potato crop

Abstract

The dissipation patterns of thiamethoxam insecticide at two different rates (12.5 and 25 µg/g) in both silty clay loam and loam soils were studied. The half lives of thiamethoxam were in the range of 15.0 to 18.8 days in silty clay loam and 20.1 to 21.5 days in loam soil. The residues of thiamethoxam in potato tubers and soil at harvest time (90 days after planting) could not be detected either in soil or in tubers at any of the applied rates (25 and 50 g a.i./ha). Thus, thiamethoxam does not appear to pose any health hazard to consumers or harm to the environment.

The route and rate of thiamethoxam soil degradation in laboratory and outdoor incubated tests, and field studies following seed treatments or spray application

“…The thiamethoxam DT 50 values derived from the OECD307 studies conducted on typical European soils lie within the typical range of thiamethoxam DT 50 values reported for laboratory studies in the literature which were derived from a range of temperature and soil moisture conditions . Full details of soils, soil treatment and incubation are not reported in the available literature studies.…”

“…This confirmed the apparent effect noted from information reported in previous literature. 6,[17][18][19][20][21] The geometric mean DT 50 value of 75.4 days for the OECD307 studies (Test 1) compares to 40.1 days for East Anglia 2 laboratory soil cores incubated in the dark under the same conditions following simulated spray applications (Test 2). However, in order to deduce the impacts of particular variables it is appropriate to examine studies in which the soil type remains the same.…”

“…The thiamethoxam DT 50 values derived from the OECD307 studies conducted on typical European soils lie within the typical range of thiamethoxam DT 50 values reported for laboratory studies in the literature which were derived from a range of temperature and soil moisture conditions. [17][18][19] Full details of soils, soil treatment and incubation are not reported in the available literature studies. However, the single soil from New Delhi, India, reported in the study of Gupta et al 18 includes a range of soil moisture conditions from completely dry to flooded and soil treatment which includes soil drying and sieving through a 2 mm sieve, as required by the OECD307 guideline.…”

“…The summary paper of Goulson reports laboratory soil degradation DT 50 values for thiamethoxam of 34 to 353 days from a number of studies. Additional laboratory soil DT 50 values under a range of soil moisture conditions ranged from 46 to 301 days at 25 °C and 15.1 to 21.5 days . Goulson also reports field DT 50 values with a range of 7 to 109 days from a single source.…”

“…Additional laboratory soil DT 50 values under a range of soil moisture conditions ranged from 46 to 301 days 18 at 25 ∘ C and 15.1 to 21.5 days. 19 Goulson 17 also reports field DT 50 values with a range of 7 to 109 days from a single source. In the study of Hilton et al 6 field soil degradation DT 50 values of 7.1 to 92.3 days (geomean 31.2 days), following normalisation to 20 ∘ C, were reported from 18 field trials performed throughout Europe.…”