Optimisation of Bacillus thuringiensis var. israelensis (Vectobac®) applications for the blackfly control programme on the Orange River, South Africa

Abstract

The Orange River, South Africa’s largest river, is a critical water resource for the country. In spite of the clear economic ben efits of regulating river flows through a series of impoundments, one of the significant undesirable ecological consequences of this regulation has been the regular outbreaks of the pest blackfly species Simulium chutteri and S. damnosum s.l. (Diptera: Simuliidae). The current control programme, carried out by the South African National Department of Agriculture, uses regular applications, by helicopter, of the target-specific bacterial larvicide Bacillus thuringiensis var. israelensis . While cost-benefit analyses show significant benefits to the control programme, benefits could potentially be further increased through applying smaller volumes of larvicide in an optimised manner, which incorporates upstream residual amounts of pesticide through downstream carry.

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