Original Research

Evaluation of larvicides in developing management guidelines for long-term control of pest blackflies (Diptera: Simuliidae) along the Orange River, South Africa

R.W. Palmer, N.A. Rivers-Moore
Onderstepoort Journal of Veterinary Research | Vol 75, No 4 | a106 | DOI: https://doi.org/10.4102/ojvr.v75i4.106 | © 2008 R.W. Palmer, N.A. Rivers-Moore | This work is licensed under CC Attribution 4.0
Submitted: 10 September 2008 | Published: 10 September 2008

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R.W. Palmer,
N.A. Rivers-Moore,

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In 2000 and 2001 Orange River levels were higher than normal: associated serious outbreaks of blackfly had a substantial detrimental impact on the local economy. The poor control was attributed to the suspected development of larval resistance to temephos. A long-term solution to blackfly control, through the identification of a suitable replacement to temephos for use during high flow conditions, was proposed. This study, however, failed to identify or register a suitable larvicide for use during high flow conditions. Although permethrin was highly effective against blackfly larvae, it was rejected because of its detrimental impacts on non-target fauna. Various formulations of locally produced dry Bacillus thuringiensis var. israelensis (B.t.i.) were tested, but these were ineffective against blackflies. The study also confirmed that resistance to temephos has developed among Simulium chutteri in the middle and lower Orange River. The feasibility of "reversing" the resistance to temephos through the use of the synergist piperonyl butoxide (PBO) was investigated, but the results were not favourable. Furthermore, PBO was highly toxic to blackflies and non-target organisms, and was not recommended for further testing. This means that B.t.i. currently remains the only symptomatic measure of treatment currently applied. Although resistance to B.t.i. has not been reported for blackflies elsewhere in South Africa, there is a need to remain vigilant and to implement an operational strategy that minimizes the risks of resistance developing.


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Crossref Citations

1. A predictive management tool for blackfly outbreaks on the Orange River, South Africa
Nicholas A. Rivers‐Moore, Trevor R. Hill
River Research and Applications  vol: 34  issue: 9  first page: 1197  year: 2018  
doi: 10.1002/rra.3357