BACKGROUND:Cashew, Anacardiumoccidentale, is aneconomically important cash crop for morethan 300 000 rural households in Tanzania. Its production is, however, severely constrained by infestation by sap-sucking insects such as Helopeltis anacardiiH. schoutedeni and Pseudotheraptus wayi. The African weaver ant, Oecophylla longinoda, is an effective biocontrol agent hemipteran pests in coconuts in Tanzania, but its efficacy in the control of Helopeltis spp. and P. wayi in Tanzanian cashew has not been investigated so far. The aim of this study was therefore to evaluate the efficacy of O. longinoda in the management these insect pests in the cashew crop at different sites of the Coast region of Tanzania. RESULTS: Colonisation levels of O. longinoda, expressed as weaver ant trails, varied from 57.1 to 60.6% and from58.3 to 67.5% 2010 and 2011 respectively. The mean number of leaf nests per tree varied from five to eight nests in 2010 and from five to nine nests in 2011. There was a negative correlation between numbers of nests and pest damage. Oecophylla longinoda-colonised cashew trees had the lowest shoot damage by Helopeltis spp. of 4.8 and 7.5% in 2010 and 2011, respectively, as opposed uncolonised cashew trees with 36 and 30% in 2010 and 2011 respectively. Similarly, nut damage by P. wayi was lowest in longinoda-colonised trees, with only 2.4 and 6.2% in 2010 and 2011 as opposed to uncolonised trees with 26 and 21%. CONCLUSION: Oecophylla longinoda is an effective biocontrol agent of the sap-sucking pests of cashew in the Coast region Tanzania and should be considered as an important component of IPM.he authors acknowledge the financial support of the Federal Ministry for Economic Cooperation and Development and the GermanAcademic Exchange Service (DAAD), Germany. They thank the International Centre of Insect Physiology and Ecology (icipe), the African Regional Postgraduate Programme in Insect Sciences (ARPPIS) and Mikocheni Agricultural Research Institute (MARI) for overall assistance during this study.