2.4.2. Cage bioassay
Efficacy of space spraying of the standard concentrations of
malathion (250 ml malathion in 5 L kerosene oil), pesguard FG
161 (d-tetramethrin + cyphenothrin) (30 ml in 5 L kerosene oil)
and deltacide (deltamethrin + s-bioallethrin + piperonyl butoxcide)
(100 ml in 5 L kerosene oil) was tested against dengue vectors in
Kurunegala municipal area using standard WHO cage bioassays
[12]. Cylindrical cages (20 cm length 5 cm diameter) prepared
using 16-mesh nylon netting were hung at 10, 25, 50, 75 and
100 m distance away from the place of insecticide fogging in
downwind direction. Three replicates were arranged for each distance.
All cages were hung 1.5 m above the ground level. Twenty
adult mosquitoes (2–3 day old) were released to each cage and fogging
was carried out by delivering standard dosages of insecticides.
The experiments were repeated in three different habitat types e.g.
open ground area, an area with little vegetation and an area with
dense vegetation. After a spray round of 8 min, cages were removed
and the mosquitoes were transferred into clean plastic cups
with 10% glucose soaked cotton pads. Mosquitoes were examined
after 1 h to determine the initial knockdowns and the mortalities
were recorded after a 24 h recovery period.