Control of Anopheles mosquitoes by ultra-low volume applications of d-allethrin and d-phenothrin in combination with larvicidings of fenitrothion in Tanzania.

Ultra-low volume (ULV) application of insecticide is widely recognized to be effective against adult mosquitoes. Hobbs (1976) reported that ULV applications of synergized pyrethrins applied with ground equipment reduced the natural population of ArnpheLes albimanus Wied.. during a heavy malaria transmission season. However, a single ULV application cannot be expected to provide lasting effectiveness. This suggests the necessity of ULV applications at appropriate intervals together with larviciding to aquatic breeding sites. In the present paper, a preliminary trial of ULV applications with a pyrethroid formulation containing d-allethrin and d-phenothrin with larvicidings by fenitrothion was carried out in an urban area of Tanzania for control of Anopheles mosquitoes. The experimental area, Buguruni Malapa vilIage, was situated in the city of Dar es Salaam, in Tanzania, East Africa. The area was about 36 ha, and included about 10,180 inhabitants and 400 houses. The average temperature and relative humidity during the trial period (June 29 to August 11, 1987) were 28.8"C and,53.07o,respectively. The rain season occurs twice a year, from March to June and October to December. In the trial area, there were 6 primaryAnophelzsbreeding sites including an open drain, a swamp, two rice fields, a ridge and a shallow well. The untreated area was set up 0.75 km from the trial area. This area included 12,798 inhabitants and 610 houses. For the ULV applications, an emulsifiable concentrate formulation containing d-allethrin and d-phenothrin at a w/v ratio of 6/14% (Pesguard@ PS201, Sumitomo Chemical Co. Ltd.) was used. One liter of Pesguard PS20l was diluted with 2 liters of water. The diluted solu-