Osservazioni sulla resistenza temporanea dei frutti di alcune specie di agrumi agli attacchi dellaCeratitis capitataWied. in Sardegna

The factors that determine the resistance of non ripen fruits of some species of citrus to the attack ofCeratitis capitataWied. have been examined. After having ascertained the lethal action of essential oils on eggs, the containance work, exercised by the thickness and in higher measure by the albedo compactness in respect to the new-born larvae, has been pointed out.The citrus resistance to the development of the juvenile stages of the fly seems bound to the fruit ripening degree, resulting highest in the unripa fruits, both for the high number of glands of essential oils per unlt of flavedo surface and for the blgger thickness and compactness of albedo. With the approaching of the physlological ripening of fruits these elements of containance of infestations decrease, making the productlon more receptlve to the Trypetid's attacks. Among the citrus species examined, those resulted more susceptible to the autumnal attacks ofCeratitis capitataare clementines and grape-fruit, while tangerine and orange have showed an higher resistance. Among the considered orange cultivars, the late cultivars of Belladonna and Valencia are resulted the most resistant to the attacks. The larval development speed ofC. capitatais resulted, under other conditions, taster in the cultivar of orange nearest to ripening and so at higher concentration of sugar. Besides the capability of Trypetid's females to choose the most dark coloured fruits for oviposition has been pointed out.