Developmental biology and substrate preference of the quarantine pest, mango pulp weevil Sternochetus frigidus (Coleoptera: Curculionidae) under laboratory conditions

The mango pulp weevil, Sternochetus frigidus (Coleoptera: Curculionidae), is a major monophagous and quarantine pest of mango ( Mangifera indica ) in tropical Asia, causing severe yield and quality losses due to its concealed feeding and development within fruit tissues. A laboratory study was conducted to investigate the developmental biology, morphometrics and substrate preference of S. frigidus using seven mango substrates: young flush, old flush, green fruit (whole and sliced), ripened fruit (whole and sliced) and stem. Experimental rearing recorded all post-ovipositional stages except the egg phase due to lack of suitable specimens and the weevil completed five larval instars with a larva to adult period of 36–47 days across substrates without significant variation. Larvae were apodous and yellowish, reaching up to 14–15 mm in length, while pupae were exarate, measuring approximately 8.8 mm in length. Adult females exhibited larger abdominal dimensions and longer antennae than males, indicating clear sexual dimorphism. Feeding and aggregation studies revealed a strong preference for sliced ripened mango fruit, followed by sliced green fruit, suggesting that exposed fruit tissues and associated volatiles strongly influence adult attraction. Infested fruits consistently showed symptoms of anthracnose, with Colletotrichum gloeosporioides identified from affected tissues, indicating that weevil feeding facilitates secondary fungal infection. The findings provide essential biological and behavioural insights into S. frigidus that are directly relevant to mass rearing, detection and the development of sustainable management strategies for mango production and quarantine protection.