Table 2.
Toxicity of 10 potential larvicidal native Bacilus thuringiensis isolates against 3rd instar larvae of Culex pipiens. Lethal concentrations (LC50 and LC95) were calculated by Probit analysis for all isolates compared to the reference Bti-H14
| Bt-code | City of collection | Hrs P-T | LC50 (μg/ml) (lower to upper) | LC95 (μg/ml) (lower to upper) | ×105 CFU/μg | Slope±SE |
|---|---|---|---|---|---|---|
| Bt-12 | Yanbu | 24 | 4.6 (4.2–5.1)e | 9.4 (7.9–11.08) | 0.53±0.4 | 5.4±0.005 |
| 48 | 2.4 (2.04–2.8) | 10.4 (8.01–13.9) | 2.6±0.06 | |||
| Bt-26 | Medina | 24 | 4.8 (4.1–5.6)e | 33.9 (21.8–54.5) | 4.1±0.7 | 1.94±0.044 |
| 48 | 1.9 (1.5–2.4) | 14.6 (10.2–22.0) | 1.9±0.051 | |||
| Bt-29 | Medina | 24 | 4.2 (3.5–5.0)e | 32.6 (22.8–47.8) | 0.52±0.1 | 1.8±0.03 |
| 48 | 2.2 (1.8–2.7) | 14.05 (10.6–19.2) | 2.05±0.037 | |||
| Bt-42 | Jizan | 24 | 2.5 (2.2–2.9)c | 15.4 (10.9–22.8) | 0.93±0.3 | 2.1±0.048 |
| 48 | 1.2 (1.04–1.35) | 3.07 (2.5–3.8) | 4.02±0.26 | |||
| Bt-44 | Jizan | 24 | 3.03 (2.7–3.4)d | 9.4 (7.7–11.6) | 0.63±0.4 | 3.35±0.075 |
| 48 | 2.08 (1.8–2.3) | 6.12 (5.1–7.5) | 3.5±0.094 | |||
| Bt-53 | Medina | 24 | 1.9 (1.7–2.2)b | 8.08 (5.8–11.7) | 1.3±0.4 | 2.6±0.0011 |
| 48 | 0.72 (0.6–0.8) | 2.5 (2.08–3.6) | 2.9±0.0014 | |||
| Bt-55 | Medina | 24 | 1.7 (1.5–1.98)b | 7.9 (6.11–10.68) | 1.95±0.3 | 2.5±0.059 |
| 48 | 1.06 (0.91–1.2) | 2.29 (2.5–3.8) | 3.65±0.21 | |||
| Bt-60 | Medina | 24 | 1.9 (1.7–2.2)b | 5.01 (4.2–6.15) | 0.13±0.1 | 4.05±0.002 |
| 48 | 0.94 (0.8–1.05) | 2.9 (2.5–3.8) | 3.3±0.09 | |||
| Bt-63 | Mecca | 24 | 0.91 (0.7–1.07)a | 5.51 (4.1–8.2) | 0.7±0.2 | 2.1±0.053 |
| 48 | 0.5 (0.4 –0.58) | 1.12 (0.95–1.4) | 4.72±0.006 | |||
| Bt-68 | Medina | 24 | 2.3 (2.06–2.7)c | 10.7 (7.8–15.7) | 1.05±0.3 | 2.5±0.055 |
| 48 | 1.1 (0.97–1.3) | 5.4 (4.2–7.5) | 2.4±0.056 | |||
| Bt-15 | Bti-H14 | 24 | 4.88 (4.2–5.4)e | 21.9 (17.3–28.0) | 4.5±0.3 | 2.52±0.044 |
| 48 | 2.62 (2.2–3.1) | 10.01 (7.8–13.2) | 2.82±0.092 |
LC50= Lethal concentration (concentration to kills 50% of test larvae), LC95= Lethal concentration (concentration to kills 95% of test larvae), CFU= colony forming unit, S.E.= Standard Error of means (n= 5), Values with different letters (a, b, c, d and e) are significantly different within strains and compared to the reference Bti-H14 (based on the non-overlapping confidence limits) according to Litchfield and Wilcoxin (1949). Control mosquitoes showed nil mortality.