Osservazioni suPlanococcus citri(Risso) nelle coltivazioni agrumicole della Sardegna

Surveys carried out in various citrus growing areas of Sardinia, including the experimental groves of Simaxis (Oristano) and Siniscola (Nuoro), revealed massive infestations ofPlanococcus citri(Risso) and general precarious state of plant health. In order to improve the situation with a rational programme of integrated control, the etiology of the insect had to be thoroughly studied while, at the same time, various test systems of control were efected. Particular attention was given to population dynamics and species interrelationships. Depending on wintering stage and microclimate,P. citriwas seen to produce 3-4 generations per annum in Sardinia, with fruit infestation begining in june when fruit diameters reached about 1 cm, the young larvae occupying exstremely protected positions. As natural control of the massive infestations proved ineffective by the indigenous parasites, (Leptomastidea Abnormis(Grlt.) andAnagyrus pseudococcl(Grlt.)), predators of the genusCrysopaand the coccidiphagous Coccinellids, (Chilocorus bipustulatus(L.) andExochomus quadripustulatus(L.)), resort was made to the introduction and dispersal ofCryptoaemus montrouzieri(Muls.) andLeptomastix dactylopii(How.). An important factor in determing fruit drop appeared to be the presence ofCryptoblabes gnidiellaMilliére, whose larvae Iive in association with the citrus mealy bug. However, no significant cross-correlation was revealed by a statistical analysis of data relative to the percentage of fruit infested byP. citriand the percentage of fruit dropped during the same period. The first attempts at Integraling chemical and biological control enabled the number of chemical intero ventions to be greatly reduced.