Table 1. Residues of imidacloprid in hive matrices resulting from feeding spiked Mega-bee diet patties and sucrose syrup to honey bee colonies for six weeks.
| Treatment a | Sample duration | Number of colonies with positive detections/total samples (Range of imidacloprid residues b (μg/kg) in positive samples) | ||||
|---|---|---|---|---|---|---|
| Bees | Beebread | Larvae | Honey | Royal jelly | ||
| Colonies fed diet patties (100 μg/kg imidacloprid) and untreated sucrose syrup | 2 weeks exposure | 6 / 8 (0.2–1.4) | 8 / 8 (0.5–1.7) | 1 / 8 (0.4) | 7 / 8 (4.7–13.4) | NA |
| 6 weeks exposure | 5 / 8 (0.5–1.9) | 8 / 8 (0.6–1.2) | 0 / 8 (ND) | 7 / 8 (2.8–10.8) | 8 / 8 (0.3–1.0) | |
| 6 weeks after exposure | 8 / 8 (0.3–0.5) | 8 / 8 (0.8–1.4) | 0 / 7 (ND) | 8 / 8 (2.3–11.7) | NA | |
| Colonies fed sucrose syrup (20 μg/kg imidacloprid) and untreated diet patties | 2 weeks exposure | 3 / 8 (0.2–0.5) | 2 / 8 (0.7–1.0) | 1 / 8 (0.5) | 4 / 8 (0.2–3.7) | NA |
| 6 weeks exposure | 0 / 8 (ND) | 3 / 8 (0.2–0.9) | 0 / 8 (ND) | 1 / 8 (0.9) | 0 / 8 (NA) | |
| 6 weeks after exposure | 0 / 8 (ND) | 2 / 8 (0.2–0.3) | 0 / 5 (ND) | 2 / 8 (0.2–0.5) | NA | |
| Colonies fed untreated diet patties and sucrose syrup | 2 weeks exposure | 4 / 8 (0.2–2.9) | 1 / 8 (1.1) | 0 / 6 (ND) | 0 / 8 (ND) | NA |
| 6 weeks exposure | 0 / 8 (ND) | 0 / 8 (ND) | 0 / 6 (ND) | 0 / 8 (ND) | 0 / 6 (ND) | |
| 6 weeks after exposure | 0 / 8 (ND) | 0 / 8 (ND) | 0 / 4 (ND) | 3 / 7 (0.2–0.3) | NA | |
aAll colonies were fed 2000 g of sucrose syrup and 400 g of diet patties weekly for six weeks; thus each colony was exposed to 40 μg of imidacloprid per week.
bLOD = 0.2 μg/kg; LOQ = 0.6 μg/kg; ND = non-detectable; NA = not sampled.