But this approach, which has been used since the middle of the last century, has not been effective with mosquitoes, owing to their fragility.
1	But	but	CCONJ	CC	_	20	cc	_	_
2	this	this	DET	DD	Number=Sing|PronType=Dem	3	det	_	_
3	approach	approach	NOUN	S	Number=Sing	20	nsubj	_	SpaceAfter=No
4	,	,	PUNCT	FF	_	3	punct	_	_
5	which	which	PRON	PR	PronType=Rel	8	nsubj:pass	_	_
6	has	have	AUX	VA	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	8	aux	_	_
7	been	be	AUX	VA	Tense=Past|VerbForm=Part	8	aux:pass	_	_
8	used	use	VERB	V	Tense=Past|VerbForm=Part	3	acl:relcl	_	_
9	since	since	ADP	E	_	11	case	_	_
10	the	the	DET	RD	Definite=Def|PronType=Art	11	det	_	_
11	middle	middle	NOUN	S	Number=Sing	8	obl	_	_
12	of	of	ADP	E	_	15	case	_	_
13	the	the	DET	RD	Definite=Def|PronType=Art	15	det	_	_
14	last	last	ADJ	NO	Degree=Pos|NumType=Ord	15	amod	_	_
15	century	century	NOUN	S	Number=Sing	11	nmod	_	SpaceAfter=No
16	,	,	PUNCT	FF	_	3	punct	_	_
17	has	have	AUX	VA	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	20	aux	_	_
18	not	not	PART	PART	Polarity=Neg	20	advmod	_	_
19	been	be	AUX	V	Tense=Past|VerbForm=Part	20	cop	_	_
20	effective	effective	ADJ	A	Degree=Pos	0	root	_	_
21	with	with	ADP	E	_	22	case	_	_
22	mosquitoes	mosquito	NOUN	S	Gender=Masc|Number=Plur	20	obl	_	SpaceAfter=No
23	,	,	PUNCT	FF	_	22	punct	_	_
24	owing	owe	VERB	V	VerbForm=Ger	22	acl	_	_
25	to	to	ADP	E	_	27	case	_	_
26	their	their	DET	AP	Poss=Yes|PronType=Prs	27	nmod:poss	_	_
27	fragility	fragility	NOUN	S	Number=Sing	24	obl	_	SpaceAfter=No
28	.	.	PUNCT	FS	_	20	punct	_	_
