Infected fruits are usually easy to distinguish from uninfested ones by the hardened, amber-coloured secretion often sculptured with two small angled tails at one end, which remains attached to the site of oviposition (Wadhi, 1964; Ridgway, 1989; Smith, 1996; Peng and Christian, 2004, 2007). Especially, when S. mangiferae populations are high, brown marks at the oviposition sites on mature fruits are very obvious (Smith, 1996; Peng and Christian, 2007). Maheswari and Purushotham (1999) described a simple method of diagnosing the incidence of S. mangiferae on mango based on the appearance of reddish-brown spots and water-soaked areas in the pulp of immature fruit. In rare instances where larvae feed and pupate within the pulp, or when they emerge from the seeds and tunnel up through the pulp, fruits are seriously damaged (Balock and Kozuma, 1964; Follett and Gabbard, 2000).

In South Africa, Kok (1979) showed that after harvest of late-maturing varieties, adults tended to leave the seed and tunnel through the fruit, leaving a scar on the outside which served as a site for secondary fungal infection; this renders the fruit unfit for human consumption. Internally infected fruit rots from the outer surface of the stone. The stones also show holes and the cotyledons turn black and become a rotten mass. Seeds fail to germinate if the embryo is damaged and the reserve of food in the cotyledons is greatly reduced.