Table 2.
Fipronil dose-response results in the susceptible Orlando Normal reference strain and five B. germanica populations recently collected from apartments in Raleigh, NC
| Straina | n | Lethal dose LD50 ng/male (95% CI)b |
Slope ± SE | χ² (df) | z-testc | RRd (95% CI) |
|---|---|---|---|---|---|---|
| Orlando Normal | 270 | 1.55 (1.32, 1.82) | 5.40 ± 0.73 | 4.00 (3) | 7.4* | - |
| VS101 | 120 | 38.2 (20.4, 71.6) | 2.58 ± 0.61 | 0.61 (2) | 4.3* | 24.7* (18.3, 33.4) |
| DR2800 | 150 | 34.6 (14.7, 81.7) | 1.56 ± 0.36 | 9.81 (2) | 4.4* | 22.4* (15.0, 33.5) |
| DR2820B | 200 | 45.4 (36.2, 56.9) | 3.92 ± 0.46 | 8.88 (3) | 8.5* | 29.3* (24.7, 34.8) |
| CC29 | 150 | 50.5 (29.2, 87.4) | 2.32 ± 0.46 | 0.38 (2) | 5.1* | 32.6* (24.9, 42.7) |
| PR515F | 150 | 57.6 (14.1, 235.4) | 2.92 ± 0.74 | 1.48 (1) | 3.9* | 37.2* (29.3, 47.2) |
The strain name was based on location. The five recently collected strains are from Raleigh, NC, collected between 2018 and 2019.
Insects were topically treated with fipronil (in 1 µl acetone); LD50 was estimated for each strain from probit analysis. CI is confidence interval. The average mass of the Orlando Normal, VS101, DR2820B, and CC29 strains were 52.1, 57.8, 52.5, and 56.4 mg/male, respectively; hence, multiply by 19.2, 17.3, 19.0, and 17.7 to obtain approximate ng/g body mass for these strains.
z-test of the slope. Values >1.96 denote a significant regression slope (*P < 0.05).
Resistance Ratios (RR, lethal dose ratio) and 95% confidence intervals. RR was calculated as LD50 of apartment-collected strain/ LD50 of susceptible reference strain (Orlando Normal). RR values with (*) are considered significant when their 95% CIs do not include 1.0 (Robertson et al. 2017).