Effect Of River Stratification on Black-Fly Population Following Application of Bacillus Thuringiensis Israelensis (Bti) on Domasi River in Zomba
Rex B. Mbewe, Themba Mzilahowa, Lawrence N. Kazembe

Abstract
Zomba District in southern Malawi was reported to have been infested with black-fly in 2006. By the year 2007, the Ministry of Health (MoH) had initiated a larviciding program using Bacillus thuringiensis Israelensis (Bti) to mitigate the effects of black-fly bites. The study aimed at assessing the impact of stratification on black-fly through monitoring of adult and larvae fly populations following Bit application. The Domasi River was divided into three strata and data on the population of black-fly was collected before and after Bit application. Larva monitoring was done using four different substrate types: nylon strips, rocks, debri and boards on upper and lower sections of the river. Adult monitoring was carried out by human landing catches. All samples collected were preserved in 75% alcohol as voucher specimen. It was concluded that stratification of the river did not have statistically significant effect on the impact of Bit on black-fly populations.

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