Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

4.12 Nezara viridula 217
Doubt has been cast (Clarke 1990) both on the policy and effectiveness
of introducing strains of T. basalis from different regions having differing
environmental conditions. This practice has either led in Australia to
effective biological control of N. viridula extending into additional
environments or, alternatively, the initial genetic make-up of T. basalis has
steadily undergone changes to allow progressive adaptation to new
environments. It is possible that T. basalis consists of a complex of sibling
species but, if not, it would be surprising if T. basalis has remained a
homogenous species worldwide. Johnson (1985) found that American
specimens of T. basalis showed much less morphological variation than
those of Africa suggesting an African origin for the species. Furthermore,
Handley (1975) reported that Australian T. basalis females would not mate
with American males, although Powell and Shepherd (1982) found that
reproductive isolation did not occur within any of 3 Australian strains
examined; or between them and a strain from Florida. Nevertheless, the
latter strain proved least fecund. Ferreira and Zamataro (1989) found no
differences in reproductive capacity or longevity between an Australian and
a Brazilian strain of T. basalis and Awan et al. (1989) concluded that Italian,
French and Spanish populations consist of a single biotype, although several
significant differences were observed in their biology. On the other hand,
differences in courtship behaviour have been observed between different
populations of T. basalis (Bin et al. 1988; Clarke and Walter 1992).
However, it is not known whether any of these differences has any
significance for biological control.
Three other wasps have been introduced, Trissolcus mitsukurii (Japan
1962), Telenomus chloropus (Japan 1962, Japan via USA 1980) and
Ooencyrtus submetallicus (West Indies 1952Ð53). Only the former is
believed to have become established but its impact has not been reported
(Field 1984; J. Turner pers. comm. 1985).
The only parasitoid reported from adult or nymphal N. viridula is the
native tachinid Cylindromyia rufifemur (Cantrell 1984; Coombs and Khan
1997). Three exotic species of parasitic tachinid fly have also been
employed in attempts at biological control of Nezara viridula, Trichopoda
pennipes from Florida, T. pilipes from the West Indies and Bogosia antinorii
from Kenya. The Trichopoda species were introduced into Australia in the
1940s and 1950s, but failed to become established (Wilson 1960). More
recently the Trichopoda species were introduced into Western Australia
from their native countries and also from Hawaii where they have been
successfully established (Michael 1981). They have not become established
in Australia. It is tempting to postulate that the pheromone blend secreted by
Australian N. viridula does not attract Trichopoda pennipes and T. pilipes