Table 1. Mean1 cotton leaf tissue concentrations of thiamethoxam and imidacloprid (±standard error of the mean) as determined by HPLC2 in 2014.
| Site (planting date) | Sampling date (days post planting) | Thiamethoxam3 (ng/g) | Imidacloprid3 (ng/g) |
|---|---|---|---|
| Chillicothe (5/19) | 6/4 (15) | 2,704 ± 836 | 2,313 ± 406 |
| 6/19 (28) | 72 ± 39 | 180 ± 91 | |
| Lamesa (5/17) | 6/10 (23) | 6,840 ± 2,912 | 1,783 ± 600 |
| 6/18 (30) | 218 ± 147 | 247 ± 136 | |
| Wall (5/23) | 6/18 (25) | 3,234 ± 317 | 1,436 ± 320 |
| 6/23 (30) | 18 ± 13 | 5.0 ± 0 | |
| Halfway (5/6) | 6/11 (35) | 18 ± 13 | 8.0 ± 3.3 |
| Kress (5/13) | 6/3 (20) | 10,618 ± 3,365 | 15,100 ± 4,885 |
Notes:
1
We used the leaf quantitation limit (five ng/g) for non-detect samples in calculating the mean.
2
The MDL for thiamethoxam and imidacloprid in leaf tissue extracts was two ng/g.
3
Based on the locations sampled twice and assuming losses followed a linear relationship, the estimated thiamethoxam and imidacloprid dissipation half-lives in cotton leaves were 4.3 and 4.5 days, respectively.