An economic study of the biological control of the spiny blackfly, Aleurocanthus spiniferus (Hemiptera : Aleyrodidae), in a citrus orchard in Swaziland

Control costs and direct crop losses die to infestations by the spiny black fly, Aleurocanthus spiniferus Quaintance, were studied in orchards of a 667 ha citrus estate, Inyoni Yami Irrigation Scheme at Tshaneni, Swaziland in the 1995/96 season the control costs and dir ect losses at this estate amou nted to R 476 000 ( approximate to US$ 86 500). This excludes the reduction in growth, the additional costs of sorting sooty mould-stained fruit and t he potential reduction in crop production of the next season. To import, re ar and establish the spiny blackfly parasitoid, Encarsia cf smithi (Silvest ri), including the project overheads, amounted to R 169 750 (approximate to US$ 30 900). Because of the classical biological control that was achieved , no chemical control of this pest was necessary during the following two s easons and no further losses of fruit were incurred due to sooty mould. The amount spent to establish biological control of the spiny blackfly, in par ts of Southern Africa, even if compared to the direct losses and control co sts of a single season on one citrus estate was exceptionally cost effectiv e. A benefit ratio was calculated at 2.8.