OLEA-EUROPAEA VOLATILES ATTRACTIVE AND REPELLENT TO THE OLIVE FRUIT-FLY (DACUS-OLEAE, GMELIN)

Comparative study of the headspace (HS) composition from olive leaves, olives of varying degrees of ripeness, and crushed olives revealed si gnificant quantitative and qualitative differences. Three different me thods were employed to test the effect of the substances identified on the behavior of Dacus oleae gravid females. Attractive/repellent feat ures were tested by presenting the insects with olfactory choices of a water solution of the test chemicals examined, water (blank), and a h ighly attractive (control) solution of olive maceration water (MW). To luene and ethylbenzene, present in leaf and half-ripe olive HIS proved attractive, while (E)-2-hexenal emitted by the crushed olives was fou nd to be decidedly repellent. An oviposition stimulation/deterrence te st was carried out on olives placed in proximity to test chemicals und er examination in water solution, with olives from the same crop servi ng as control. In the oviposition test alpha-pinene, mostly emitted by the leaves and half-ripe olives, emerged clearly as an activant, p-xy lene, myr-cenone, ethylbenzene, n-octane and o-xylene as weak activant s. (E)-2-hexenal and hexanal, both emitted by the crushed olives, disp layed an oviposition deterrent effect. The highly repellent property o f (E)-2-hexenal was again confirmed in this test.