Abstract:Aphelinus mali (Haldeman) is an important parasitoid of Eriosoma lanigerum (Hausmann). The natural control effect of A.mali on E.lanigerum in apple orchards in Laiyang, Shandong Province and overwintering eclosion rate of A.mali under different protective measures were studied. The results showed that two peaks of E.lanigerum occurred from late May to late July and from mid September to mid October. The parasitoid could control E.lanigerum to some extent in the whole year. Its natural parasitism rate reached the peak up to 50%-90% from early July to early September, while the control vacancy appeared in the period from April to May. In the chemically controlled apple orchard, the number and parasitism rate of A.mali decreased because of chemical pesticides. Overwintering eclosion rate was higher when some protective measures were taken, e.g. attaching grass around trunks or depositing the black "pupa" parasitized by A.mali indoors or on south slope of open field. This could increase the number of alive parasitoids after overwintering, thus enhance its control efficiency on E.lanigerum.