Abstract: This study aims to understand the aphids on Populus alba var. pyramidalis shelterbelts and understory weeds and their conservation effects on natural enemies. With the P. alba var. pyramidalis shelterbelts in Shaya County weeded or not, the population dynamics of aphids and natural enemy insects on 5 species of weeds, including Phragmites australis, Cynanchum acutum, Sphaerophysa salsula, Lactuca tatarica, and Cirsium japonicum, were surveyed regularly. The results showed that the aphid densities on P. alba var. pyramidalis shelterbelts with weeds and without weeds were 158.64 and 60.00 per plant, respectively. The aphid densities on the 5 species of weeds on the understory ranked as: P. australis (12.76 per plant)>C. acutum (11.09 per plant)>S. salsula (0.38 per plant)>L. tatarica (0.09 per plant)>C. japonicum (0.02 per plant). The population densities of Oenopia conglobata, Chrysopidae and Syrphidae on P. alba var. Pyramidalis shelterbelts with weeds were 0.20, 0.27 and 0.01 per plant, respectively, while on shelterbelts without weeds, the population densities were 0.10, 0.11 and 0.02 per plant, respectively. The 5 species of understory weeds had a certain conservation effect on predatory Coccinellidae and Chrysopidae, and the P. australis had some conservation effect on Syrphidae. Chrysopidae was the most dominant in the P. alba var. pyramidalis shelterbelts. Understory weeds had an important impact on the species, population dynamics and population densities of insects in shelterbelts. In terms of biodiversity, shelterbelts with weeds were better than shelterbelts without weeds. The aphids in the shelterbelts have conserved natural enemy insects to a certain extent, so it is recommended that the understory weeds not be removed unless necessary or be weeded selectively in the management of P. alba var. pyramidalis shelterbelts to conserve natural enemy insects.

Key words: Populus alba var. pyramidalis Bunge, shelterbelts, predatory natural enemy, population dynamic