Table 2 Relative toxicity of five insecticides to two strains of S. zeamais [i.e., the pyrethroids susceptible (SzSusc) and pyrethroid resistant (SzPyrSel) strains] and two strains of S. oryzae (i.e., SoPyrTol and SoPyrR).

From: Diversity and convergence of mechanisms involved in pyrethroid resistance in the stored grain weevils, Sitophilus spp.

Insecticide

Sitophilus strains

No. of insects

LD50 (95% FI) mg a.i/kg of grains

LD95 (95% FI) mg a.i/kg of grains

RR50 (95% CL)

RRa50 (95% CL)

Χ 2

P

Deltamethrin

SzSusc

493

0.68 (0.5–0.9)

1.6 (1.2–2.8)

*

*

7.42

0.09

SzPyrSel

(—)

(—)

(—)

(>2500)

(>2500)

(—)

(—)

SoPyrTol

490

25.95 (23.1–28.5)

82.5 (69.3–106.7)

*

37.6 (35.1–40.3)

2.20

0.53

SoPyrR

495

69.39 (64.2–76.0)

201.8 (159.8–291.5)

2.7 (2.4–2.9)

101.0 (91.2–110.9)

1.54

0.67

Lambda-Cyhalothrin

SzSusc

526

0.71 (0.7–0.8)

1.5 (1.3–1.7)

*

*

4.31

0.23

SzPyrSel

(—)

(—)

(—)

(—)

(—)

(—)

(—)

SoPyrTol

596

12.06 (10.1–13.9)

54.4(45.3–69.1)

*

16.9 (15.9–18.0)

1.57

0.81

SoPyrR

588

174.3 (146.1–219.6)

1243.1(973.4–2259.0)

14.5 (9.8–21.2)

244.6 (167.5–357.3)

4.46

0.61

Indoxacarb

SzSusc

689

0.40 (0.3–0.5)

5.2 (3.9–7.4)

*

*

6.77

0.24

SzPyrSel

599

3.79 (3.1–4.5)

15.3 (12.9–19.1)

9.5 (7.8–11.5)

9.5 (7.8–11.5)

1.67

0.80

SoPyrTol

496

3.05 (2.6–3.5)

11.2 (9.3–14.2)

*

7.6 (6.3–9.6)

1.06

0.78

SoPyrR

512

1.55 (1.2–1.9)

14.2 (10.6–20.5)

0.5 (0.5–0.6)

3.9 (3.2–4.8)

4.72

0.45

Imidacloprid

SzSusc

617

1.21 (0.9–1.7)

13.0 (6.6–41.9)

*

*

3.82

0.43

SzPyrSel

496

0.83 (0.7–3.4)

15.5 (9.60–18.3)

0.7 (0.5–1.1)

0.7 (0.5–1.1)

5.63

0.13

SoPyrTol

398

1.32 (0.2–5.2)

14.2 (8.50–19.4)

*

1.1 (0.17–2.3)

1.40

0.49

SoPyrR

450

1.54 (0.5–4.1)

16.6 (11.2–25.1)

1.2 (0.6–5.1)

1.3 (0.27–2.1)

1.34

0.85

Thiamethoxam

SzSusc

497

0.68 (0.6–0.8)

2.6 (2.1–3.7)

*

*

2.79

0.43

SzPyrSel

404

1.46 (1.1–2.0)

15.6 (8.4–41.9)

2.2 (1.7–2.8)

2.2 (1.7–2.8)

2.21

0.33

SoPyrTol

597

1.95 (1.5–2.9)

25.3 (11.9–90.9)

*

2.9 (1.9–4.2)

4.10

0.39

SoPyrR

449

0.94 (0.69–1.2)

12.8 (7.3–38.2)

0.48 (0.3–0.7)

1.4 (1.1–1.7)

3.12

0.53

Spinosad

SzSusc

635

15.7 (14.5–16.9)

37.3 (32.5–45.5)

*

*

7.36

0.12

SzPyrSel

522

23.6 (21.2–27.3)

80.2 (57.9–141.6)

1.5 (1.2–1.8)

1.5 (1.2–1.8)

6.07

0.11

SoPyrTol

499

17.2 (13.8–20.7)

80.5 (64.6–107.5)

*

1.1 (0.7–1.3)

1.88

0.59

SoPyrR

512

21.5 (19.3–26.6)

76.1 (69.7–82.4)

1.25 (0.9–8.3)

1.3 (1.2–1.7)

4.28

0.34

  1. FI = Fiducial Intervals; RR50 = Resistance ratio determined by LD50 of given population/LD50 of most susceptible population (*); RRa50 = Resistance ratio determined by LD50 of given population/LD50 of SzSusc; 95% CL = 95% Confidence limits; χ2 = Chi-square for lack-of-fit to the probit model, and P = Probability associated with the chi-square statistic. (—) Data not available as no dose-response curve could be computed for the selected population SzPyrSel.
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