Abstract: The Willow Oyster Scale,Lepidosaphes salicina Borchs.(Homopter:Diaspididae)was studied in the "Three North"Protective Forest of China during 1987 -1990. It has one generation a year and overwinters as egg under the scale in Shenyang. The females lay eggs under the scale about 84 eggs on average.The sex ratio is 0.55 (♀♀/100).The important natural enemies found are the predacious mite,Hemisarcoptes malus (Acari:Hemisarcoptidae),which reduced the pest population by 41.6%;Aphycis proclla (Hymenoptera:Aphelinidae) and Chilocorus kumance(Coleoptera:Coccinellidae).A bufferointmenc insectcide was tested and used for controlling the pest in the field,a 92.2% - 97.2% mortality was obtained after 8 - 20 days.The population density was lowered significantly three years later. The distribution,damage,biology,of the pest were involved.

Key words: Lepidosaphes salicina, Poplar, Bionomics, Biological and chemical control