Abstract: Semiochemicals perform the key physiological functions in the course of interactions between insects and plants. Bioassay studies showed that the avoidance of tomato plant from oviposition by cabbage butterfly was proved to be attributed to the presence of water-soluble deterrent which could be extracted by ethanol. Oviposition deterrent indices (ODI) of the ethanol extract (Ee) were 87.4 % and 80.9 % respectively in the first day and third day after treatment, both were statistically significant . The active water-soluble fractions when applied on cabbages not only significantly reduced the amount of eggs laid on the cabbage leaves, but also strongly disturbed their normal oviposition behavior in contrast to the controls. Net-house tests showed that a formulation of the active water-soluble components with Tween-80 (Ee+0.1% Tween-80) may be hopeful to be developed as an 0viposition-deterrent which keeps effective for more than a week when applied on cabbages.

Key words: Pieris rapae, Lycopersicon esculentum, extracts, ovipositiov-deterring activity