Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

4.12 Nezara viridula 223
parasitisation (49.9%) than rafts placed in the canopy of macadamia trees
(14.7%). Predators were more effective at locating rafts placed in trees than
in weeds and were always more efficient than T. basalis, regardless of their
location. The egg parasitoid, Anastatus sp. was equally inefficient in both
habitats. In 1990 only 1.2% of the eggs in the trees were parasitised and 8.6%
in the weeds. During the same period, predators destroyed 26.0% and 14.5%
in trees and weeds respectively.
In 1991 parasitisation of eggs dropped to 0.2% and 1.7% in trees and
weeds, whereas predation increased to 47.7% and 36.9% respectively.
Doubt was, therefore, cast upon T. basalis having a prominent role in
biological control of N. viridula in Hawaii (Jones 1995). Although this
conclusion appears to follow in the macadamia agroecosystem studied, it
would be of interest to know whether it applies also to other susceptible
crops. Predation was attributed mainly to ants, including Pheidole
megacephala.
INDIA
Singh (1973) reported no parasitoids in life-table studies of N. viridula on
soybeans.
INDONESIA
Partial life tables showed on soybeans in Northern Sumatra that mortality of
N. viridula until the late 1st instar was 50 to 87%, of which 18 to 85%
occurred during the egg stage and was caused mainly by predators. Only 2 to
26% of the eggs were parasitised. The main predators were two species of
ants (Solenopsis geminata and Dolichoderus sp. a staphylinid beetle
(Paederus sp.) and several crickets, although other egg predators belonging
to the families Tettigoniidae, Lygaeidae and Anthocoridae were also
observed feeding on the eggs. Trissolcus basalis parasitised the eggs but no
evidence was obtained of the presence of tachinid parasitoids that attack late
nymphs and adults (van den Berg et al. 1995).
ITALY
Before production of soybeans began in Italy in 1981 N. viridula was only
important occasionally. Crops attacked included tomatoes and legumes. The
increasing production (over a decade more than a thousand fold increase in
area planted to soybeans) filled a temporal and food gap for N. viridula and
other pentatomids (Colazza and Bin 1990). The second generation of
N. viridula now migrates each summer into soybeans at the beginning of
development of pods, which then provide the main food for reproduction
and larval development. Abundance of N. viridula increased steadily in the
eighties throughout northern and central Italy to a level at which it became a
key pest. Three parasitoids were recorded from egg rafts, Anastatus
bifasciatus, Ooencyrtus sp. and Trissolcus basalis. However the first 2