Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

4.4 Aphis gossypii 71
the posterior of the mummy. Aphidiid mummies are round and usually
straw-coloured to brown and in some genera (e.g. Ephedrus) always black
and parchment-like. Aphelinid larvae do not spin cocoons, and their
mummies are usually slender and black (Takada 1992).
The chain of events that determines host specificity includes, in
sequence, host habitat finding, host finding, host acceptance by the
parasitoid and host suitability.
The last larval instar of some parasitoids provokes their aphid hosts to
move away from the plant on which they were feeding. With Lysiphlebus
fabarum, Ephedrus plagiator and Trioxys angelicae this migration of premummies
is connected with diapause (under conditions of a short day) or
with aestivation (under conditions of a long day). Parasitoids usually emerge
without delay from aphids which become mummies where they have been
feeding (Behrendt 1968).
Starù (1970) provides additional details of many of the species of
Aphidiidae that follow below and HŒgvar and Hofsvang (1991) a
comprehensive review of their biology, host selection and use in biological
control.
Aphelinus abdominalis (= A. flavipes) Hym.: Aphelinidae
This species is widespread in Europe and is recorded also from USSR, India,
Australia and Israel. It is extensively distributed in India as one of the
important parasitoids of Myzus persicae and A. gossypii. It becomes active
in late May and is abundant during June and July. The incubation time for
eggs is 2 days and adults emerge after 13 days in September (Ramaseshiah
and Dharmadhikari 1969).
When an Indian strain was liberated in a U.K. glasshouse at 23¡C, one
week after artificially infesting plants with A. gossypii, it was unable to
overtake the pest population because the rate of increase of the pest was
scarcely affected by the parasitoid. Only when aphid overcrowding occurred
and rate of increase was self-limited, did the parasiteÕs rate of increase (6 ´ per
week) exceed that of the aphid. Reducing the glasshouse temperature to 19¡C
slowed the rate of aphid increase and permitted the parasitoids to contain the
pest before severe leaf-distortion occurred. On the other hand, when
parasitoids were present at the time that A. gossypii was introduced, aphid
reproduction was suppressed and effective control resulted (Hussey and
Bravenboer 1971).
Aphelinus gossypii Hym.: Aphelinidae
This species was described from Hawaii and is recorded from Australia,
New Zealand, India, Japan and also from Tonga, where it was reared in
abundance from Aphis gossypii on taro (Colocasia esculenta). It is probably