Abstract: For the adults of phytophagous insects, their experience of non-host plant-originated re-pellent/deterrent may produce habituation or induced preference to it. In this study, the experi-enceinduced changes in oviposition responses of diamondback moth Plutelle xylostella L. to a neem-based repellent BIOACT-T^TM EC508 were examined in laboratory. 2—6 days old female moths were offered with 2—6 times or 2—6 days experience of the repellent, and their ovipostion preference to untreated and BIOACT-treated Chinese cabbages were evaluated. The results showed that BIOACT had a strong repellent effect to all of the naive 2—6days old females, that only laid approximately 10% of their eggs on BIOACT-treated plants. As for the 2, 4 and 6 days old females who experienced 2 times or 2 days, 4 times or 4 days, and 6 times or 6 days of BIOACT, their mean oviposition rate on BIOACT-treated plants increased to 17%, 21%—24%, and 29%, re-spectively,demonstrating that this experience of the females induced their habituation or preference to BIOACT, and consequently, the repellent effect of BIOACT decreased. However, there were substantial variations in the experience-induced changes of oviposition preference among the individuals of the moth.

Key words: N₂O emission, Cropping system, Paddy soil, Water regime