The present study constitutes the first attempt to construct a photographic map of the polytene chromosomes of Dacus oleae, a pest of the olive tree that causes serious financial damage in all olive oil producing countries. The map was constructed by using the larval fat body cells, the chromosomes of which are representative of the polytene chromosomes of other polytene tissues. In addition, the mitotic chromosomes of brain ganglia were examined, permitting tentative correlations between mitotic and polytene elements. This investigation shows that D. oleae is suitable for cytogenetic analysis in both mitotic and polytene chromosomes, a fact that may prove very useful for obtaining more detailed genetic information on the pest's natural populations.

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Lavandula stoechas, a native plant of Greece, is rich in essential oil and fenchone is its major constituent. We examined the effect of the essential oil and its main constituents on soil metabolism and microbial growth. Addition of the essential oil or fenchone to soil samples induced a remarkable increase in soil respiration. This was accompanied by an increase in the soil bacterial population of three orders of magnitude. This sizable population was not qualitatively similar to that of the control soil samples. One bacterial strain dominated soil samples treated with L. stoechas essential oil or fenchone. By use of the disk diffusion assay, we evaluated the capacity of three bacterial strains that we isolated from the soil samples, as well as Escherichia coli and Bacillus subtilis (reference strains), to grow in the presence of the essential oil and three of its main constituents (fenchone, cineol, alpha-pinene). The substances tested did not inhibit the growth of the strain found to dominate the bacterial populations of treated soil samples; they severely inhibited B. subtilis. The other two isolated strains could also grow in liquid cultures in the presence of different quantities of essential oil or fenchone. Addition of fenchone at the end of the exponential phase increased the cell numbers of the strain that dominated the bacterial populations of treated soil samples, indicating use of the substrate added. On the basis of these results, we propose a scheme of successional stages during the decomposition process of the rich-in-essential-oil litter of aromatic plants that abound in the Mediterranean environment.

A survey of Bacillus thuringiensis recovered from the environments of olive groves in Greece was carried out. Of 80 soil samples, 24 were found to contain B. thuringiensis with parasporal crystal inclusions; these were tested for toxicity against the olive fruit fly (Dacus okae). Mortality levels of larvae caused by the different isolates varied from 7 to 87%. Higher levels of mortality were observed if a mixture of relatively pure crystals and spores was used compared with the mortality resulting from either fraction alone. We were able to show that the toxicity of the most active isolate is likely to be specific for D. oleae.

Bacillus thuringiensis, isolate 114A, was used in toxicity experiments against the wild population ofthe olive pest Bactroceria oleae (Gmelin). In laboratory experiments, spores and crystals of the B.t. were delivered to the insects with the food. Longevity, oviposition period, number of eggs produced, and percent hatch were recorded. Olive fruits from the oviposition test were dipped into a suspension containing spores and crystals of B. thuringiensis 114A after the eggs were deposited. In field experiments, four to six sprayings per year of B.t. 114A isolate were applied for three successive years. It was found that, in addition to the longevity of B. oleae, the oviposition period, number of eggs and percent egg hatch decreased. Also, the percentage of pupation and emergence was reduced when olive fruits with eggs in their mesocarp were dipped in the solution of spores and crystals. Field applications with the toxins of 114A isolate of B. thuringiensis have resulted in significant protection of the olive production.