All field experiments aimed to test whether dispensers loaded with synthetic pheromone presented at a test station attracted more females and males than simultaneously presented solvent-only controls. Stations consisted of boxes constructed from four panels of thick (10mm) plywood (55cm (width) by 105cm (height)), held together by plastic garden ties sewn through holes (1.5mm ID) drilled in the corner of each plywood panel. Each panel had three holes (10cm ID) drilled in a horizontal line across the middle to allow host odour to escape. Two opposing panels in each box had a groove across the top edge, onto which a wooden pole could be secured and a trap suspended.
At dusk (17:00-18:00), pairs of experimental stations (test and control) were placed 3m apart in residential gardens, previously identified by the local disease control authority (Centro de Controle de Zoonoses (CCZ)) as sites of sand fly aggregation in or around chicken coops. We began by using lures in conjunction with modified (Natal et al. 1991 ) CDC miniature light traps, recognized as an effective device for sampling sand fly populations. Traps, powered overnight by 6-volt rechargeable batteries, were fitted with 35cm-diameter metal lids, and suspended from the pole above each station. Captured flies were collected in pots (10cm diam × 8cm height) connected to each trap via a nylon sleeve (10cm diam). A chicken, selected at random from the garden, was placed in each box to provide a source of host odor.
A dispenser containing 50μg of synthetic pheromone was attached to the underside of the lid at each test station, and a dispenser containing solvent only was similarly positioned at each control station.
The next morning (07:00-08:00) nylon sleeves were tied with string to prevent collected flies from escaping, before pots and batteries were removed. Chickens were freed from boxes, dispensers removed from lids. The positions of test and control boxes was alternated between nights. Flies were identified as male or female L. longipalpis and counted in the laboratory under x40 magnification, and trap batteries recharged before reuse. This entire first trial was repeated a second time, with the light bulbs, which are attractive when lit, removed.
Under natural conditions, male sand flies only aggregate on or near host animals, and host odor has been shown to synergize female attraction to sex pheromone in the laboratory (Bray and Hamilton 2007 (link)). However, females can also be attracted to pheromone alone in the laboratory. To test the attractiveness of synthetic pheromone without host odor in the field, the first two experiments were repeated without chickens in test stations.
Finally, to test whether pheromone could be used to trap flies in conjunction with a cheaper alternative to mechanical light traps, the first trial (with chickens) was repeated, replacing CDCs with blue, 28cm wide agricultural sticky traps (Russell IPM, Deeside, UK) wrapped around the top of each box. Each morning, sticky traps were numbered and covered with clear film, before being removed to the laboratory for counting.
Each experiment was conducted over two to four nights, using six to seven pairs of boxes spread across two to three gardens. New dispensers were used for each night of experiments. Wilcoxon signed rank tests (Sokal and Rohlf 1995 ) compared numbers of flies captured at test and control boxes in each pair. Males and females were analyzed separately, and pairs excluded from analysis if at least one of the traps did not function correctly.
At dusk (17:00-18:00), pairs of experimental stations (test and control) were placed 3m apart in residential gardens, previously identified by the local disease control authority (Centro de Controle de Zoonoses (CCZ)) as sites of sand fly aggregation in or around chicken coops. We began by using lures in conjunction with modified (Natal et al. 1991 ) CDC miniature light traps, recognized as an effective device for sampling sand fly populations. Traps, powered overnight by 6-volt rechargeable batteries, were fitted with 35cm-diameter metal lids, and suspended from the pole above each station. Captured flies were collected in pots (10cm diam × 8cm height) connected to each trap via a nylon sleeve (10cm diam). A chicken, selected at random from the garden, was placed in each box to provide a source of host odor.
A dispenser containing 50μg of synthetic pheromone was attached to the underside of the lid at each test station, and a dispenser containing solvent only was similarly positioned at each control station.
The next morning (07:00-08:00) nylon sleeves were tied with string to prevent collected flies from escaping, before pots and batteries were removed. Chickens were freed from boxes, dispensers removed from lids. The positions of test and control boxes was alternated between nights. Flies were identified as male or female L. longipalpis and counted in the laboratory under x40 magnification, and trap batteries recharged before reuse. This entire first trial was repeated a second time, with the light bulbs, which are attractive when lit, removed.
Under natural conditions, male sand flies only aggregate on or near host animals, and host odor has been shown to synergize female attraction to sex pheromone in the laboratory (Bray and Hamilton 2007 (link)). However, females can also be attracted to pheromone alone in the laboratory. To test the attractiveness of synthetic pheromone without host odor in the field, the first two experiments were repeated without chickens in test stations.
Finally, to test whether pheromone could be used to trap flies in conjunction with a cheaper alternative to mechanical light traps, the first trial (with chickens) was repeated, replacing CDCs with blue, 28cm wide agricultural sticky traps (Russell IPM, Deeside, UK) wrapped around the top of each box. Each morning, sticky traps were numbered and covered with clear film, before being removed to the laboratory for counting.
Each experiment was conducted over two to four nights, using six to seven pairs of boxes spread across two to three gardens. New dispensers were used for each night of experiments. Wilcoxon signed rank tests (Sokal and Rohlf 1995 ) compared numbers of flies captured at test and control boxes in each pair. Males and females were analyzed separately, and pairs excluded from analysis if at least one of the traps did not function correctly.
