Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Natural enemies
4.13
Ophiomyia phaseoli
More than 50 parasitic Hymenoptera have been reported from bean fly
(Table 4.13.1), almost all emerging from pupae, arising from eggs laid in
host larvae. No egg parasitoids are known and no dipterous parasitoids have
been recorded. Although figures for percent parasitisation are unavailable
from many countries where bean fly occurs, the levels recorded are
generally unimpressive, often less than 30%. The outstanding exception is
the 90% or more, often produced by the braconid Opius phaseoli in East
Africa and Ethiopia (Greathead 1969; Abate 1991) and similar levels from
Opius phaseoli and Eurytoma sp. in the Agra region of India (Singh 1982).
AUSTRALIA
Although Tryon (1895), who described Ophiomyia phaseoli from
Queensland specimens, believed it to be native to Australia, it has never been
recorded extensively from indigenous plants (Kleinschmidt 1970), so is
unlikely to have evolved there. Twelve parasitoids (two of them possibly
hyperparasitoids) (Table 4.13.1) emerged from O. phaseoli pupae taken
mainly from cowpea ( Vigna unguiculata).
A later re-examination of
Australasian Chalcidoidea by Bou‹ek (1988) indicates that only 11 species
were actually involved and none were hyperparasitoids. Bou‹ek (1988) lists
one additional parasitoid, the eurytomid Plutarchia bicarinativentris, which
also occurs in Papua New Guinea. The braconid Opius oleracei, which
attacks bean fly, has also been recorded from the widespread agromyzid
Chromatomyia horticola (= Phytomyza atricornis).
EAST AFRICA
Ophiomyia phaseoli was not reported in Uganda until the 1920s, Tanzania
until 1937 and Kenya until 1939. It occurs in close association with
Ophiomyia spencerella and also with O. centrosematis,
a species which is
known also from Indonesia.
The bean fly is very heavily attacked in all climatic zones by the braconid
Opius phaseoli (usually of the order of 70% to 90% and even up to 94.4%
parasitisation), and relatively lightly (3% to 9%) by Opius importatus,
by a
polyphagous pteromalid near Herbertia sp. (less than 1%) and by an
assemblage of chalcidoids. Puparia are also consumed by ants. Three wasps
found in small numbers were considered to be hyperparasitoids, namely
Norbanus sp. (Pteromalidae), Eupelmus sp. nr australiensis (= E. sp. nr
popa)
(Eupelmidae) and Pediobius sp. (Eulophidae). In spite of the heavy
parasitisation by Opius phaseoli,
sufficient bean flies survive in some
seasons to cause heavy infestations of plantings. These parasitoids are thus,
at times, unable to prevent economic damage (Greathead 1969).
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