Ovipositional preferences were significantly affected by the water treatment, plant age, and site for oviposition. Female moths preferred to oviposit on six-week-old, non-stressed plants of B. napus compared to the water-stressed counterparts. On average, 2.15 times more eggs were laid on non-stressed plants than the water-stressed ones. Similarly, 1.58 times more eggs were laid on host plant upper leaf surface than on the lower leaf surface. This study determined that P. xylostella females preferred to deposit eggs on six-week-old vigorous plants not under water stress to ensure the successful development and survival of their offspring.