Intercrops grown under immature rubber are virtually unaffected by competition as the inter row space receives sufficient light and the interference from rubber roots is low at this stage. But when rubber trees mature canopies close and rubber roots spread into the inter row space interfering the growth and yield of intercrops. The combined effect of these factors will be envisaged as competition, affecting the performance of intercropping rubber trees (Pathiratna and Perera, 2003; Pathiratna, 2006).