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Survey of blackfly (Diptera : Simuliidae) annoyance levels and abundance along the Vaal and Orange Rivers, South Africa
Blackflies (Diptera: Simuliidae) are pests in the livestock and labour-intensive farming systems
along the major rivers in South Africa. Since 1995, blackflies have been controlled in the
Orange River with the larvicide Bacillus thuringienses var. israelensis (Bti). During 2006–2007,
the views of livestock farmers concerning blackfly annoyance were determined by means of
questionnaires. The results of the questionnaires were substantiated by seasonal abundance
surveys of the sub-adult stages of blackflies, conducted in 2007 at 13 sites in the Orange River
and 11 sites in the Vaal River. More than half (52%) of the 39 participating farmers along
the Orange River and 79% of the 52 participating farmers along the Vaal River stated that
they experienced severe blackfly problems. The majority of farmers were unaware of the
availability of products that could be used to protect their animals against blackfly attacks
and were willing to be involved in blackfly research. High numbers of blackfly sub-adult
stages found in both rivers supported the high annoyance levels reported by the respondents.
Simulium chutteri, Simulium damnosum s.l., Simulium hargreavesi, Simulium adersi and Simulium
alcocki were identified at Christiana and Delportshoop on the Vaal River, whilst S. chutteri,
S. damnosum s.l., S. adersi, S. alcocki and Simulium gariepense were identified at Marksdrift
and Ses Bridge on the Orange River. Despite the extensive control of blackflies, farmers still
experience problems and this contention is supported by surveys conducted along the rivers.
Description:
C.J.d.B. (Onderstepoort Veterinary Institute) wrote the
manuscript as fulfilment for an MSc degree within the
Department of Veterinary Tropical Diseases at the University
of Pretoria, for which K.K.G. (University of Pretoria) was the
study supervisor.