Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

228 Biological Control of Insect Pests: Southeast Asian Prospects
Biology of the major species
Scelionidae: Hymenoptera
This is the most important family of hymenopterous parasitoids emerging
from the eggs of N. viridula and is dealt with, amongst others, by Nixon
(1935, 1936, 1937, 1966).
Trissolcus basalis
Kamal (1937) was the first of many to make a detailed study of the impact of
the egg parasite Trissolcus basalis on the abundance of Nezara viridula: no
control measures are needed in Egypt. His work on the biology of the wasp
has been supplemented by studies by many later workers (e.g. Wilson 1961;
Cumber 1964; Powell and Shepherd 1982; Correa and Moscardi 1993, 1994;
Awadalla 1996; Colazza et al. 1996b). The minute female of T. basalis
oviposits in the side of the bug egg, after which she marks the egg by rubbing
an abdominal secretion over it with the ovipositor, as a deterrent to other
females from laying in the same egg. The length of the life cycle ranges from
9 to 24 days depending on temperature, the entire egg, larval and pupal
stages being passed inside the same eggshell. The adult wasps chew their
way out through the lid of the eggshell, males usually emerging first and
disputing with one another for possession of the egg batch and thereby the
right to fertilise the later-emerging females. In hot weather the females live 4
to 15 days and have considerable dispersive powers, as shown by the
rapidity with which they spread through newly colonised areas. The adult
wasps overwinter among leaves and litter.
As indicated earlier, there is good evidence for the existence of several
different strains of T. basalis. Experimental work using strains from three
widely separated regions of Australia and from Florida showed that they
were not reproductively isolated, that the Australian strains had a higher
fecundity, but that adults of the Florida strain lived longer (Powell and
Shepherd 1982).
T. basalis is frequently recorded from several other pentatomids, but has
a special preference for N. viridula (Jones 1988). It appears to be most
effective in coastal and subcoastal areas and has been established in
Argentina, Australia, Fiji, Hawaii, Kiribati, Papua New Guinea, New
Caledonia, Samoa, Solomon Is, South Africa and Tonga and possibly in
several other countries (Table 4.12.2).
In Australia two species of the pteromalid Acroclissodes are parasitic on
T. basalis (Clarke and Seymour 1992).