Mir S. Mulla*
Jittawadee Rodcharoen**
Wichai Kong-ngamsuk***
Apiwat Tawatsin***
Prakong Phan-Urai***
Usavadee Thavara***

Affiliations :
      *Department of Entomology, University of California, Riverside, CA 92521
      **Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
      ***Division of Medical Entomology, Department of Medical Sciences, NIH, Ministry of Public Health, Nonthaburi, Thailand

Source:
      Journal of the American Mosquito Control Association 1997; 13(4): 297-304

Language:
      English

Abstract:
      Two newly developed Bacillus sphaericus  larvicidal formulations, VectoLex CG® (Corncob granules) and VectoLex WDG® (water dispersible granules), were tested against Culex quinquefasciatus   larvae in 4 highly polluted breeding sites in Thailand. VectoLex CG, applied at rates of 0.5-2 g/m², gave satisfactory to complete control of late-instar larvae and pupae for up to 4 wk after treatment. The VectoLex WDG, which had higher potency and was applied at rates of 0.1-0.5 g/m², gave satisfactory control for 1-4 wk after treatment. Among the factors influencing longevity of control were dosage of a given formulation, precipitation, and flooding of the treated sites; the latter had the greatest impact. Presence of larvivorous fish did not seem to influence larval populations because there were heavy populations of mosquito larvae present in the test sites in the presence of moderate numbers of fish before the application of B. sphaericus   treatments.