Target pest: Nezara viridula (Hemiptera: Pentatomidae), green vegetable bug
Agent introduced: Trissolcus basalis (Hymenoptera: Scelionidae) = Microphanurus basalis, Asolcus basalis
Australia (originally from Egypt)
Cameron et al. (1989) - Trissolcus basalis [as Microphanurus basalis] was imported from Australia; from a single importation of 200-300 eggs [three parasitised egg masses (Cameron et al. (1993)] in January 1949 more than 40,000 parasitoids were reared for release. Several strains had been imported into Australia. In 1933 it was imported from Egypt to Western Australia, from where it was redistributed within Australia until about 1945. Further strains were imported from 1956 to 1963 which appeared to improve control of N. viridula in inland areas with relatively cold winters. In 1984 strains from USA, Brazil and South Africa were imported into southeastern Queensland. The material introduced into New Zealand was obtained from CSIRO at Canberra and presumably originated from naturalised Australian strains [presumably from the Egyptian material, the only introduction into Australia prior to the 1949 introduction to New Zealand] which may have been susceptible to cooler winters.
Cameron et al. (1989) - released in February and March 1949 at seven sites in Northland and one each at New Plymouth (Taranaki) and Opotiki (Bay of Plenty), with over 40,000 parasitoids released in total. Redistribution was carried out until 1959 and by 1964 the parasitoid had been released in all areas where N. viridula was abundant (throughout the North lsland and Nelson in the South Island).
Cameron et al. (1989) - recoveries were made soon after releases in Paihia (Northland) in 1950, Onehunga (Auckland) in 1951 and Nelson in 1960. It was considered that by 1967 T. basalis was present throughout the range of N. viridula.
Impacts on target:
Cameron et al. (1989) - Trissolcus basalis is considered to give effective control of N. viridula in some locations, and the degree of control may have increased for several years following introductions. In 1953 Cumber recorded 90% of egg masses parasitised at Paihia, Northland and considered that a 'high measure of control' had been achieved. However, little is known about the variability in effectiveness of T. basalis in different areas of New Zealand. Since the decline of the pest status of N. viridula in New Zealand, sporadic outbreaks are confined to areas of warm climate and susceptible crops. The decline of populations of N. viridula following the introduction of T. basalis in New Zealand parallels that achieved in parts of Australia, though the contribution of T. basalis to this decline is unknown. It is possible that the T. basalis population in New Zealand has limited adaptability as the result of the original introduction of a few individuals of one strain.
Cameron et al. (1993) - Trissolcus basalis is categorised as exerting â€śpartialâ€ť control (defined as â€śadditional control remains commonly necessary butâ€¦pest outbreaks occur less frequentlyâ€ť) over N. viridula.
Impacts on non-targets:
Cameron et al. (1989) - Trissolcus basalis has been shown to be capable of parasitising other pentatomid species in New Zealand.
Cameron et al. (1993) - the introduction of T. basalis against N. viridula followed examination of the host relationships of the parasitoid, which demonstrated that this species parasitised eggs of the native pest Glaucias amyoti, and a native predator Cermatulus nasalis, but did not attack endemic Rhopalimorpha spp. These results represented an environmental risk analysis on which ecologists at the time  judged that there were net benefits to be obtained from the introduction. Since its introduction into New Zealand, T. basalis has been recorded from non-target species, including non-pest species, but this host range was predicted prior to introduction.
Cameron PJ, Hill RL, Bain J, Thomas WP (1989). A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424p.
Cameron PJ, Hill RL, Bain J, Thomas WP (1993). Analysis of importations for biological control of insect pests and weeds in New Zealand. Biocontrol Science and Technology 3(4): 387-404