Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

234 Biological Control of Insect Pests: Southeast Asian Prospects
T. giacomelli Argentina; and Ectophasiopsis arcuata: Chile. These 4 are
reported to be more abundant now on N. viridula than on the native bugs
they parasitised before the arrival of N. viridula (Jones 1988). A problem in
their effective use is that location of N. viridula hosts is dependent, in some
species at least, upon the secretion by N. viridula of a specific attractive
blend of chemicals. Some biotypes of N. viridula that do not produce the
appropriate blend largely escape oviposition. There are no records of
tachinids regularly attacking N. viridula in the East Asian Region, except for
the widespread, polyphagous Gymnosoma rotundata, which was found to
cause up to 5% parasitisation of N. viridula in Japan and also to attack
N. antennata in Japan and Korea (Kiritani et al. 1963).
The main areas where N. viridula continues to be an economically
important pest in spite of attempts to use natural enemies including
T. basalis appear, with the exception of certain crops such as macadamia and
pecan nuts, to be associated with extensive plantings of soybeans. A detailed
re-examination is required of the behaviour of T. basalis (and perhaps other
egg parasitoids) in relation to ability to parasitise N. viridula egg masses laid
on soybean. If it is demonstrated that certain physical or chemical
characteristics of soybeans are responsible for poorer than usual
performance, serious consideration should be given to the selection of
varieties that have minimal adverse effects on the parasitoids. This, of
course, is different from selecting soybean cultivars that are resistant to
N. viridula, some of which are known (e.g. Kester et al. 1984; Bowers 1990).
In this context it is relevant that the biology of Telenomus chloropus, an
egg parasite introduced into southern USA in 1982 from Japan, was studied
on eggs of N. viridula that had been reared on the stink bug-resistant
soybean, PI 717444, or on the susceptible cultivar, Davis. Time of
development of the parasite did not differ significantly in eggs from either
source, but success of emergence was lower from eggs laid on resistant
soybean and fecundity of those that did emerge was about half of that of
individuals reared from eggs laid on Davis. The authors (Orr et al. 1985b)
point out that, with a marked reduction in emergence and fecundity,
combined with decreased host availability, there is the potential for
reduction or elimination of resident parasite populations in fields of resistant
soybeans.
Comparatively little is known of the range of Nezara parasitoids in its
centre of origin, namely the Ethiopian region, although at least 6 Scelionidae
including T. basalis have been recorded, together with the apparentlyspecific,
widespread tachinid Bogosia antinorii, whose effectiveness
deserves study. It is probable that a thorough investigation in the Ethiopian
region would disclose an additional range of potentially valuable species.