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 import in 1980 for biological control of Dialeurodes citri, a serious pest of citrus. The larvae of D. citri secrete honeydew, which is colonized by sooty 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 economic damage threshold for several years. This study, carried out in a citrus orchard during the years 1987-1991, was intended to demonstrate the existence of efficient biological control by comparing the pest populations before and after the unhindered introduction of the natural enemy to a new region. In the course of two years, the pest population decreased from a peak level of 122 eggs to 2-7 per half-leaf. Concurrently, the population of the 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 peaks 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.