Mahogany shoot borer, Hypsipyla robusta. is a serious pest of mahogany trees, whereas neem Azadirachta indica and sentang A. excelsa trees are sources of natural pesticides and insect repellents. Companion planting of these trees to protect mahogany plantations has been proposed as a control method, but so far no field experiment to test this possibility has been carried out. The present study, however, confirmed by three series of field experiments that·mahogany (Swietenia macrophylla) trees alternately planted with neem (A. indica) or sentang (A. excelsa) were seriously attacked by the borer, indicating that companion planting of Azadirachta species does not protect mahogany from the borers attack.