Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Attempts at biological control
4.13 Ophiomyia phaseoli 249
The only introductions for biological control of bean fly (Table 4.13.2) have
been of the two braconid parasitoids Opius phaseoli and O. importatus from
Uganda to Hawaii in 1969 (Davis 1971, 1972; Greathead 1975; Funasaki et
al. 1988) and of O. phaseoli from Hawaii to Taiwan in 1974Ð75 (N.S.
Talekar pers comm. 1994). In Hawaii both species rapidly became
established on Oahu and host density was soon markedly reduced. They
were introduced to other islands and, by 1971, on Kauai 100% of bean flies
sampled produced parasitoids: on Maui rates ranged from 25% to 83%. No
differences in the incidence of parasitisation were detected when
infestations on French bean and cowpea were compared. By 1973
O. importatus had become the dominant parasitoid and the polyphagous
Halticoptera patellana (which was already present) was only rarely
encountered (Greathead 1975). Surveys by Raros (1975) in 1973 and 1974
of three locations on Oahu revealed average parasitisation ranging from
8.3% to 23.5%, a result Talekar (1990) suggested might have been due to the
heavy use of insecticides diminishing the earlier effectiveness of the
parasitoids. In 1994 the bean fly was reported to be still a problem on young
seedlings, so that farmers usually apply one or two insecticide sprays after
seedlings emerge above the ground. Once the bean plant has developed a
couple of leaves the fly is no longer a problem (W.C. Mitchell pers. comm.).
Opius phaseoli was not recovered in Taiwan for the first two years after its
introduction in 1974Ð75 from Hawaii, but there have been recent reports of
its presence, in spite of the current excessive use of insecticides against bean
fly (N.S. Talekar pers. comm. 1994).