Table 2.

Western corn rootworm adult susceptibility of pyrethroid-resistant (R-) and pyrethroid-susceptible (S-) populations estimated in 2017 for insecticide active ingredients.

Insecticide	Population	Na	Slope ± SE	LC50 (95% CI)b	χ² (d.f.)	RR50 (95% CI)c
Bifenthrin	S-Lab1	120	3.30 ± 0.53	0.19 (0.14–0.24)	1.19 (2)	1	—	—
	S-Lab2	180	1.57 ± 0.23	0.32 (0.19–0.47)	2.86 (4)	1.66 (1.00–2.76)	1	—
	S-Field	151	2.21 ± 0.36	2.49 (1.85–3.31)	0.42 (3)	13.08 (9.05–18.91)	7.89 (4.64–13.41)	1
	R-Lab	151	4.79 ± 1.21	7.23 (5.00–8.86)	1.65 (3)	37.92 (26.98–53.29)	22.86 (13.70–38.12)	2.90 (2.00–4.20)
	R-Field1	121	2.97 ± 0.53	7.55 (5.46–9.63)	0.33 (2)	39.60 (27.66–56.69)	23.87 (14.13–40.31)	3.03 (2.05–4.46)
	R-Field2	121	1.74 ± 0.40	10.49 (6.14–17.18)	0.79 (2)	55.05 (32.53–93.14)	33.18 (17.32–63.55)	4.21 (2.44–7.27)
Dimethoate	S-Lab2	150	3.29 ± 0.58	0.20 (0.15–0.24)	2.72 (3)	1	—	—
	S-Lab1	150	6.58 ± 1.82	0.37 (0.30–0.42)	1.57 (3)	1.87 (1.46–2.41)	1	—
	S-Field	120	11.75 ± 1.94	0.98 (0.92–1.05)	1.61 (2)	4.95 (3.96–6.18)	2.64 (2.28–3.06)	1
	R-Field1	181	3.09 ± 0.37	2.85 (2.33–3.47)	2.97 (4)	14.36 (10.74–19.21)	7.67 (6.05–9.72)	2.90 (2.36–3.57)
	R-Field2	153	3.41 ± 0.62	3.23 (2.36–4.06)	2.69 (3)	16.30 (11.68–22.76)	8.70 (6.52–11.61)	3.30 (2.53–4.29)
	R-Lab	121	2.57 ± 0.43	4.48 (3.44–5.64)	1.57 (2)	22.60 (16.40–31.15)	12.07 (9.18–15.86)	4.57 (3.57–5.85)
Indoxacarb	S-Lab2	152	2.66 ± 0.41	7.40 (3.90–11.19)	3.78 (3)		1	—
	S-Field	150	3.14 ± 0.58	7.62 (5.79–9.93)	0.28 (3)		1.03 (0.72–1.47)	1
	R-Field1	150	1.66 ± 0.31	2.47 (1.14–4.00)	2.81 (3)		0.33 (0.18–0.63)	0.32 (0.17–0.61)
	R-Lab	151	1.76 ± 0.27	2.58 (1.80–3.53)	1.66 (3)		0.35 (0.23–0.52)	0.34 (0.22–0.51)

^aNumber of insects tested; ^bμg a.i./vial; ^cresistance ratios relative to each S- population.