Table 1 Relative toxicity of four insecticides (i.e., lambda-cyhalothrin, imidacloprid, thiamethoxam and spinosad) to 14 Brazilian strains of S. zeamais.

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

Insecticide type

S. zeamais strains

No. of insects

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

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

RR50 (95% CL)b

Χ 2

P

Lambda-cyhalothrin

Amambai-MS

519

1.6 (1.3–1.8)

7.8 (6.2–10.5)

5.4 (4.0–7.3)

6.05

0.11

Balsas-MA

521

0.7 (0.6–0.9)

1.6 (1.3–2.3)

2.6 (1.9–3.4)

6.31

0.10

Barreiras-BA

629

1.0 (0.9–1.1)

4.7 (3.8–6.3)

3.5 (2.6–4.8)

4.23

0.38

Canarana–MT

420

0.8 (0.7–0.9)

2.6 (2.2–3.2)

2.8 (2.1–3.8)

1.03

0.60

Cristalina-GO

318

0.7 (0.2–1.2)

3.2 (2.5–4.9)

2.6 (1.7–4.0)

2.28

0.56

E. S. Pinhal-SP

521

0.9 (0.7–1.1)

2.5 (1.7–6.2)

3.1 (2.3–4.3)

8.62

0.10

Ipojuca-PE

417

2.0 (1.7–2.3)

8.7 (6.9–11.7)

7.1 (5.3–9.7)

1.77

0.41

Iragassu-PE

629

1.0 (0.9–1.1)

2.4 (2.1–2.8)

3.6 (2.7–4.9)

4.51

0.34

Jacarezinho-PR (SzPyrR1)

627

2.8 (2.4–3.2)

17.6 (13.6–24.4)

9.9 (7.3–13.5)

5.59

0.24

Juiz de Fora-MG(SzPyrR2)

423

5.4 (4.9–6.2)

16.7 (13.7–21.8)

19.5 (14.4–26.4)

3.96

0.14

Piracicaba-SP

515

0.9 (0.8–1.0)

2.0 (1.7–2.4)

3.4 (2.5–4.5)

3.43

0.33

Sao João-PR

630

1.2 (1.0–1.4)

12.9 (8.7–22.5)

4.3 (3.1–5.8)

2.85

0.58

Teresina-PI

415

0.3 (0.2–0.4)

4.1 (2.7–7.7)

*

2.64

0.24

Xapuri-AC

526

1.0 (0.9–1.1)

2.0 (1.8–2.5)

3.6 (2.7–4.9)

3.68

0.30

Sete Lagoas–MG (SzSusc)

526

0.71 (0.7–0.8)

1.5 (1.3–1.7)

2.6 (1.9–3.5)

4.31

0.23

Imidacloprid

Amambai-MS

622

4.3 (3.5–5.2)

53.1 (34.2–104.5)

2.7 (1.8–4.1)

2.04

0.73

Balsas-MA

405

2.3 (1.6–2.9)

22.7 (15.8–39.6)

1.4 (0.9–2.2)

3.64

0.70

Barreiras-BA

507

2.2 (1.5–2.7)

38.4 (22.9–92.7)

1.3 (0.9–2.0)

6.17

0.10

Canarana–MT

399

1.9 (0.9–3.6)

12.5 (5.6–21.9)

1.2 (0.6–2.3)

2.73

0.26

Cristalina-GO

420

1.9 (1.7–2.5)

13.4 (11.7–15.2)

1.2 (0.9–2.5)

4.85

0.31

E. S. Pinhal-SP

619

1.6 (0.8–2.4)

11.3 (4.9–28.7)

*

3.00

0.56

Ipojuca-PE

409

3.1 (2.3–4.0)

48.3 (29.2–108.4)

1.9 (1.3–3.0)

2.54

0.76

Iragassu-PE

619

2.4 (1.7–2.9)

34.1 (22.6–65.0)

1.5 (1.0–2.2)

2.93

0.57

Jacarezinho-PR (SzPyrR1)

510

1.7 (1.2–2.2)

11.9 (8.0–24.9)

1.1 (0.6–2.0)

2.42

0.49

Juiz de Fora-MG (SzPyrR2)

414

2.7(1.9–3.5)

61.1 (34.1–161.4)

1.7 (1.1–2.6)

2.02

0.36

Piracicaba-SP

617

5.7 (4.8–6.8)

76.5 (46.8–162.0)

3.6 (2.3–5.6)

1.97

0.91

Sao João-PR

623

5.1 (4.4–5.9)

47.3 (32.7–80.6)

3.2 (2.1–4.8)

4.03

0.40

Teresina-PI

607

2.0 (1.4–2.6)

39.6 (25.08–82.8)

1.3 (0.8–1.9)

2.29

0.68

Xapuri-AC

509

2.6 (2.0–3.1)

33.4 (21.2–70.2)

1.6 (1.1–2.4)

2.91

0.41

Sete Lagoas–MG (SzSusc)

617

1.21 (0.9–1.7)

13.0 (6.6–41.9)

0.8 (0.5–1.2)

3.82

0.43

SzPyrSel

496

1.83 (0.7–3.4)

15.5 (9.6–18.3)

0.5 (0.34–0.78)

5.63

0.13

Thiamethoxam

Amambai-MS

736

0.85 (0.7–1.1)

8.4 (4.8–18.9)

2.5 (2.1–3.0)

8.71

0.12

Balsas-MA

523

1.07 (0.97–1.3)

7.2 (4.6–14.3)

3.1 (2.7–3.6)

5.52

0.14

Barreiras-BA

493

0.46 (0.4–0.5)

2.7 (2.1–3.8)

1.4 (1.2–1.6)

4.64

0.20

Canarana–MT

502

0.70 (0.6–0.8)

1.5 (1.3–2.1)

2.1 (1.8–2.3)

1.87

0.60

Cristalina-GO

501

0.59 (0.5–0.7)

5.9 (4.1–9.9)

1.7 (1.5–2.1)

4.38

0.22

E. S. Pinhal-SP

598

0.34 (0.3–0.4)

2.2 (1.8–2.9)

*

4.67

0.32

Ipojuca-PE

605

1.29 (1.1–1.5)

7.0 (4.9–12.7)

3.8 (3.3–4.3)

2.86

0.41

Iragassu-PE

679

0.50 (0.4–0.6)

2.9 (2.0–5.1)

1.5 (1.3–1.7)

9.50

0.09

Jacarezinho-PR (SzPyrR1)

595

0.87 (0.8–0.9)

4.9 (3.7–7.5)

2.6 (2.3–2.9)

4.28

0.37

Juiz de Fora-MG (SzPyrR2)

499

1.25 (1.1–1.5)

8.1 (5.5–14.4)

3.7 (3.2–4.2)

2.26

0.52

Piracicaba-SP

622

0.98 (0.8–1.1)

9.6 (6.3–17.9)

2.9 (2.5–3.3)

3.44

0.49

Sao João-PR

595

0.39 (0.3–0.5)

2.3 (1.9–3.0)

1.2 (1.0–1.3)

4.71

0.32

Teresina-PI

595

0.49(0.4–0.6)

2.8 (2.3–3.8)

1.5 (1.3–1.7)

1.92

0.75

Xapuri-AC

494

0.56 (0.4–0.74)

1.8 (1.30–4.42)

1.6 (1.4–1.9)

7.16

0.07

Sete Lagoas–MG (SzSusc)

497

0.68 (0.6–0.8)

2.6 (2.1–3.7)

2.1 (1.8–2.3)

2.79

0.43

SzPyrSel

404

1.46 (1.1–2.0)

15.6 (8.4–41.9)

4.3 (3.2–5.7)

2.21

0.33

Spinosad

Amambai-MS

612

12.3(10.6–13.7)

49.2 (39.3–70.1)

1.3 (1.2–1.4)

7.68

0.10

Balsas-MA

504

16.4(18.5–18.0)

63.8 (48.0–102.3)

1.7 (1.5–1.9)

5.71

0.13

Barreiras-BA

520

13.1(8.8–16.1)

228.1 (99.2–372)

1.4 (0.8–2.5)

1.85

0.61

Canarana–MT

627

11.9(10.5–13.0)

36.1 (31.1–45.0)

1.2 (1.1–1.3)

6.28

0.18

Cristalina-GO

595

9.60 (8.3–10.8)

32.6(26.9–43.2)

*

1.89

0.76

E. S. Pinhal-SP

418

27.3 (22.5–32.6)

107.1 (58.7–195.2)

1.1 (1.0–1.3)

7.94

0.10

Ipojuca-PE

519

24.7 (21.1–30.4)

62.6(41.0–109.1)

0.9 (0.8–1.0)

6.85

0.08

Spinosad

Igarassu-PE

525

22.7(21.3–24.6)

53.0 (45.0–66.6)

2.4 (2.2–2.6)

4.14

0.25

Jacarezinho-PR (SzPyrR1)

632

30.7 (25.5–36.9)

293.7 (134.9–354.1)

0.9 (0.7–1.0)

1.23

0.87

Juiz de Fora-MG (SzPyrR2)

614

27.2 (23.4–32.4)

154.4 (91.7–416.7)

2.8 (2.1–3.9)

3.99

0.14

Piracicaba-SP

615

18.8 (15.2–20.8)

83.0 (60.2–142.1)

2.0 (1.7–2.3)

4.29

0.37

Sao João-PR

519

19.5(17.4–22.2)

98.6 (65.5–207.1)

2.0 (1.7–2.5)

2.01

0.57

Teresina-PI

526

19.3(15.9–22.7)

45.7 (33.4–124.8)

2.0 (1.8–2.2)

6.90

0.08

Xapuri-AC

496

20.4 (19.2–21.7)

42.6 (37.5–50.42)

2.1(2.0–2.3)

3.76

0.29

Sete Lagoas–MG (SzSusc)

635

15.7 (14.5–16.9)

37.3 (32.5–45.5)

1.6 (1.5–1.8)

7.36

0.12

SzPyrSel

522

23.6 (21.2–27.7)

37.3 (32.5–45.5)

2.5 (2.0–3.0)

6.07

0.11

  1. aFI = Fiducial Intervals; bRR50 = Resistance ratio determined by LD50 of given population/LD50 of most susceptible strain (note the asterisks for each insecticide type); 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. SzPyrSel = the S. zeamais laboratory strain selected for pyrethroid resistance.
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