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

Table 3

Susceptibility of field populations of B. cucurbitae (collected during 2007) to spinosad by topical application at 24 h after treatment in Taiwan.

Location	Regression parameters						RR^a
	𝑁	Slope ± SE	LD50 (ng/fly) (95% FL)^1		𝜒^2	𝑛
Lab.	280	2.54±0.31	2.42	(1.99–3.01) a	1.93	280	—
Hsinchu	200	3.36±0.39	9.13	(7.73–11.0) c	2.92	240	3.77
Nantou	240	1.79±0.22	4.59	(3.36–5.96) b	2.15	280	1.90
Changhwa	200	2.20±0.31	4.63	(3.69–6.12) b	1.76	240	1.91
Yunlin	240	2.48±0.39	2.71	(1.96–3.41) ab	1.51	240	1.12
Kaohsiung	240	2.35±0.46	4.08	(2.36–5.53) ab	1.76	240	1.69
Pintung	200	2.77±0.32	19.6	(13.9–28.6) d	3.71*	240	8.10

*The asterisk (*) indicates a significant difference at 𝑃<0.05 (χ² test) comparing the responses actually observed in the bioassay to the regression line from the probit analysis.
¹The RR is given as the values of LD_{50  of wild population}/LD_{50  of laboratory strain} to spinosad for the indicated post treatment time points.
²Within the LD column, different letters after the parentheses indicate significantly different LD₅₀ values, as 95% FL did not overlap.