Worse, in South Africa, weevils tunnel through the flesh of late maturing fruit attracting fungal infections. Its presence affects fruit quality: consumers are unlikely to welcome fruit if i) there are dark marks over the eggs on the surface of the fruit, or ii) life forms of the weevil or frass are visible in the seed. However, the weevil remains a 'cosmetic' pest. Further, there is little apparent damage to the flesh from tunnels made by the larvae the tunnels close as the fruit expands, and are no longer seen at maturity. The weevil does not cause significant loss of production, although it can increase fruit drop during early development, and reduce germination. In India, for instance, levels of infestation can be close to 90%. The adults do not move far from the tree where they developed, and this is the reason for "hot-spots" of the weevil within mango plantations. Survival during the winter months is in leaf litter, under bark, in the forks of branches, or within the seed. Spread is inside infested fruit transported for eating and propagation. Adults are not strong flyers. The life cycle from egg to adult is 5-8 weeks. Usually, there is just one adult in each fruit. The adult emerges by chewing through the seed coat up to 2 months after the fruit has fallen on the ground and the flesh has decayed. Pupation occurs in the seed, rarely in the flesh, and lasts about 7 days (Photos 4&5). When mature, the larvae are up to 18 mm long. The eggs hatch and the larvae burrow through the flesh and into the seed, where they feed on the immature leaves (Photo 3). After laying an egg, the female weevil makes a slit in the fruit to release sap which covers the egg and "glues" it to the fruit. At this time, the adults start to feed on leaves and shoots, mate and lay eggs.Įggs are laid singly on young fruit (about 30 mm diameter), up to the stage when they are half mature. Hibernation ends when flowering and fruiting begins. It has been suggested that periods of hibernation and activity are associated with day length. In the Northern Territory of Australia, this is between December and mid-August. The adults hibernate during the non-fruiting period. The adults are 7.5-10 mm long and about 4 mm wide, with wing cases of variable colour: dark brown, black, grey, with light (yellowish) patches (Photo 1&2). The damage is done by the larvae tunneling into the seed. Note, there is another mango weevil, the mango pulp weevil, Sternochetus rigidus, present in South and Southeast Asia, including Papua New Guinea. It is recorded from Australia (but not Western Australia), Fiji, French Polynesia, Guam, New Caledonia, Northern Mariana Islands, Tonga, and Wallis and Futuna. Asia, Africa, North, (Hawaii), South, and Central America, the Caribbean, Oceania. Sternochetus mangiferae previously, Cryptorhynchus mangiferae. Mango seed weevil, mango stone weevil, mango weevil Scientific Name Close-up of Photo 3, showing pupa of the mango seed weevil, Sternochetus mangiferae, inside a mango seed.
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