Attracting adult New World screwworm,Cochliomyia hominivorax,to odour-baited targets in the field

Abstract. A field study in Libya investigated aspects of Cochliomyia hominivorax behaviour relevant to the operation of a target-based control system. Flies were readily caught by electrified targets, but only when baited with the attractant ‘swormlure-4’. Target size (0.25-lm²) did not affect catch, but black targets caught twice as many flies as red ones. Omitting the most volatile component of swormlure-4, dimethyl disulphide, significantly reduced catches of both sexes of C. hominivorax in wind-orientated traps, but only reduced the capture of females significantly on targets. A new polythene sachet dispenser for odours was tested; four to six such sachets filled with swormlure-4 less dimethyl disulphide gave an equivalent catch to one of the standard bottle plus wick dispensers using the same attractant, although they dispensed odour at about half the rate. From direct observations, fewer than 40% of flies contacted the target for more than 10 s on any one visit. From catches on an intermittently-active electrocuting grid, it was calculated that there is a c. 40% rate of multiple contacts of flies with the target.