MOSQUITOCIDAL EFFICACY OF Bacillus thuringiensis SUBSP. israelensis BASED FORMULATIONS PRODUCED IN VIETNAM

Abstract

Bacillus  thuringiensis  subsp.   israelensis  strain   Bti-11   based   biological   mosquito larvicides  produced  in  Vietnam  in  different   slowly  released  solid  formulations  were laboratory  evaluated  activity  against  main  vector  mosquitoes. Anopheles minimus, Aedes aegypti,  Culex quinquefasciatus.  The formulations  were made  in the  small  round  cake  form with  3  cm  diameter,  2  mm  -  5  mm  thickness.  Raw  materials  used  were  cheap  and available  in  Vietnam:  com  cob,  sugar  cane  bagasse,  cork,  popcorn.  Results  showed  that the formulation  made  of com  cob (CTI)  and  of sugar cane bagasse  and  polyvinylalcobol adhesive  (CT4)  got  the  highest  efficacy,  96.6  and  100% respectively.  In  experiment  for long-term  effect  of  products,  the  formulations  CTI,  CT4  and  CT7  had  high  efficiency maintenance,   larvae   mortality   was   95%  after   11  days.  The   formulation   CT4   was remarkably  degraded  after   11  days,  while  the  formulation   CTI   was  not  noticeably
degraded.  The  formulation  CTI  was  used  for  field  trail  in  some  ponds  in  urbanizing areas in Thanh  Xuan  district,  Hanoi  city. Mosquito  larvae  density  in experimental  ponds reduced   from   90.85  to   100%)  after   72  hours  of  treatment.  These  indicate  that  Bti preparations  produced  in Vietnam  have  high  efficacy  in the  field  condition  and  could  be promising products for  mosquito  control  programs.