| Abstract: | Summary In 1967 the artificial biological control against the olive fly was undertaken in Palermo (Sicily) on about 300,000 olive
trees, grown in an area of about 2,800 hectares, partly on dry soil and partly on irrigated soil.
From June 26th until October 31th 32,000,000Opius concolor Szepl.siculus Mon. were released, which had been produced in special insectaries onCeratitis larvae.
In 1967 theDacus oleae infestation was tardy on the whole; nevertheless, in some biotopes of the area covered by olive trees where the biological
control was carried out, olives infested withDacus could observed since June 20th with eggs and larvae in the first stage.
In September and October the olive fly was present in all olive groves of the coastal and hill areas and immediately multiplied
and spread to such a point that between September 15th and October 15th most of the olives had fallen to the ground and almost
100% of those that had remained on the trees were infested withDacus.
The results of the biological control have been, on the contrary, most satisfactory and the olives in the entire area not
only were almost completely healthy for the most part, but nearly all of them had remained on the trees until the crop was
gathered.
In 1967 the cost of the biological control amounted to Lit. 81 per tree and Lit. 0.60 perOpius produced, with a considerable saving as compared to1966.
It is remarkable that about 100Opius were released per tree in 1967, whereas in 1966 about 28 had been released per tree.
The good results of the biological control much depend on the mass releases made at the beginning of July in order to check
the firstDacus generation; mass releases should be made also when apparently there are noDacus in the olive grove and the olives are for the most part intact.
The biological control undertaken in Sicily against theDacus in 1967 is the first large-scale application of this control method in Europe and the results obtained clearly prove the
certainty that by this method olives can be protected against theDacus and men defended against the residual toxic products, at less cost than that required for a chemical control.
|
