Monitoring Resistance to Spinosad in the Melon Fly (Bactrocera cucurbitae) in Hawaii and Taiwan

Table 5

Susceptibility of field populations of B. cucurbitae, collected during 2007 in Taiwan, to spinosad and other insecticides analyzed by topical application assay at 24 hr after treatment.

Insecticide and location	Regression parameters						RR^a
	𝑁	Slope ± SE	LD50 (95% FL)^1		LD90 (95% FL)
Fenthion
Lab.	320	5.07±1.12	15.4	(11.1–18.0) a	27.5	(24.0–35.0)	—
Hsinchu	200	4.13±0.51	29.1	(25.0–33.6) b	59.4	(49.1–78.2)	1.89
Nantou	240	3.45±0.49	30.8	(25.3–36.9) b	72.5	(57.5–104)	2.00
Changhwa	200	3.35±0.39	32.9	(28.0–39.0) b	79.4	(63.3–110)	2.14
Yunlin	240	3.30±0.42	21.0	(14.8–28.7) ab	51.3	(35.8–109)	1.36
Kaohsiung	152	3.56±0.64	32.3	(27.1–40.2) b	73.9	(54.8–132)	2.10
Pintung	200	5.50±0.74	88.3	(66.7–119) c	151	(114–303)	5.73
Malathion
Lab.	280	6.07±0.68	353	(322–387) a	574	(509–679)	—
Hsinchu	200	3.94±0.48	367	(315–426) a	775	(638–1030)	1.04
Nantou	280	2.12±0.26	508	(408–658) a	2050	(1390–3720)	1.44
Changhwa	200	3.27±0.37	427	(361–505) a	1050	(840–1450)	1.21
Yunlin	240	3.40±0.41	871	(639–1170) b	2080	(1470–4100)	2.47
Kaohsiung	200	4.41±0.58	871	(755–1010) b	1700	(1410–2270)	2.47
Pintung	200	5.11±0.68	1142	(998–1300) b	2040	(1720–2610)	3.24

^aResistance ratios (RR) toward insecticides are compared with the LD₅₀ (95% FL) of laboratory line (lab.) in Taiwan.
¹Within each insecticide, different letters after the parentheses indicate significantly different LD₅₀ values, as 95% FL did not overlap.