Abstract: A field study on the life table of diamondback moth (DBM) Plutella xylostella showed that the population increase index of DBM in chemical control plot was 52.52, while that of four continuous generations of DBM in ecological restoration plot was 16.9, 7.16, 3.71 and 4.02, respectively, indicating that the control effect of natural enemies on target pest was greatly improved. The main factor affecting the first and forth generations of DBM was the parasitism of Cotesia plutella, while those affecting the second and third generations of DBM were the predator of the 4^th instar larva and the parasitism of Trichogramma, with the corresponding exclusive index of population control (EIPC) being 1.39, 1.54, 1.56 and 1.74, respectively. There was an obvious time lag effect of natural enemies on their target pest, and thus, to protect and multiply the population of natural enemies in the field should be the key point of fully exerting the potential of natural enemies in their pest control.

Key words: Drought stress, Germination, Caragana korshinskii, Hedysarum scoparium, Artemisia sphaerocephala