Università degli studi di Sassari, Facoltà di Agraria - Gallizzi
Abstract
Surveys carried out in various citrus growing areas of Sardinia, including the experimental groves of Simaxis
(Oristano) and Siniscola (Nuoro), revealed massive infestations of Planococcus 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. citri was 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.) and Anagyrus pseudococcl (Grlt.)), predators of the genus Crysopa and the coccidiphagous
Coccinellids, (Chilocorus bipustulatus (L.) and Exochomus quadripustulatus (L.)), resort was made
to the introduction and dispersal of Cryptoaemus montrouzieri (Muls.) and Leptomastix dactylopii
(How.).
An important factor in determing fruit drop appeared to be the presence of Cryptoblabes gnidiella Milliére,
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 by P. citri and 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
