Citrus snow scale, Unaspis citri (Comstock) (Homoptera: Diaspididae) has been a major pest of citrus in eastern Australia, only partially under biological control and difficult to control with pesticides. Between 1977 and 1988, five parasitoid species were introduced (all southeast Asian in origin) but none successfully controlled the scale. In 1990, the ladybird Chilocorus circumdatus Gyllenhal (Coleoptera: Coccinellidae) was first observed in Queensland feeding on U. citri. During 1990-1991,

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... t was field collected and laboratory reared, released and established in citrus areas throughout Queensland. C. circumdatus gave good control of the scale in most cases within two years of establishment. Ladybird numbers averaged 20 per tree in subcoastal orchards and about 5 per tree in coastal orchards (with lower scale infestations). Populations in some heavily infested orchards were estimated at up to 1000 ladybirds per tree. The ladybirds were persistent and there usually remained a few per tree even when the scale was reduced to a low level. The biology of the ladybird is discussed and other control agents of U. citri listed.