Introducing Encarsia lahorensis against Dialeurodes citri in Israel: a case of successful biological control

The parasitoid Encarsia lahorensis has been present in Israel since its imp ort in 1980 for biological control of Dialeurodes citri, a serious pest of citrus. The larvae of D. citri secrete honeydew, which is colonized by soot y mould fungi, leading to aesthetic impairment of the fruit as well as leaf drop and yield loss. In a process which took about 3 years, the parasitoid reduced the pest to low levels and maintained the population beneath the e conomic damage threshold for several years. This study, carried out in a ci trus orchard during the years 1987-1991, was intended to demonstrate the ex istence of efficient biological control by comparing the pest populations b efore and after the unhindered introduction of the natural enemy to a new r egion. In the course of two years, the pest population decreased from a pea k level of 122 eggs to 2-7 per half-leaf. Concurrently, the population of t he vulnerable fourth nymphal instar decreased from a maximum of 12 to 3 per half-leaf. Thereafter, D. citri was maintained at this low level, with pea ks of parasitism ranging from 20 to 50%. It was concluded that D. citri is under successful biological control in Israel by the specific parasitoid E. lahorensis.