Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

248 Biological Control of Insect Pests: Southeast Asian Prospects
Chiang et al. (1978) surveyed the parasitoids of three agromyzids
infesting mungbean, namely Ophiomyia phaseoli, O. centrosematis and
Melanagromyza sojae. Parasitisation fluctuated considerably, surpassing
60% during July, but declining to nearly 0% in December and January. Since
there was a negative correlation between agromyzid populations and percent
parasitisation it was concluded that parasitoids played a role in controlling
agromyzid populations.
THAILAND
Surveys in several regions of Thailand for natural enemies of the major pest
of soybean (Ophiomyia phaseoli) revealed 5 species of hymenopterous
parasitoid and a nematode (Burikam 1978). The most important species
were Plutarchia indefensa (Eurytomidae) and Fopius sp. (Braconidae). A
eulophid, a pteromalid and a cynipid were less important (Burikam and
Napompeth 1979; Napompeth 1994). Parasitisation by P. indefensa
averaged 52.8% and two samples gave 7.5% and 5.9% for Fopius sp.
(Burikam 1978), although Napompeth (1994) later considered the two
species to be of equal importance. The cynipid wasp also attacked the bean
stem miner Melanagromyza sojae. On one occasion pupae containing 20 to
50 nematodes were recorded, with a pupal parasitisation rate of 4.6%
(Burikam 1978). A life table analysis showed that there was a densitydependent
factor regulating bean fly populations (Burikam and Napompeth
1979).
Unless Fopius sp. (Braconidae) proves to be Opius phaseoli
(Braconidae) (which is present in both India and the Philippines), it appears
that O. phaseoli may not be widespread throughout Southeast Asia and may
be well worth distributing more widely. The identity of the Fopius sp. is to
be investigated (B. Napompeth pers. comm. 1994).
ZIMBABWE
Phaseolus spp. are the principal host crops damaged, but cowpeas (Vigna
sinensis) and soybeans (Glycine soja) are also attacked. Plantings in late
summer are usually only lightly infested and a braconid, identified as Opius
liogaster (but quite possibly O. phaseoli), exercises effective control in most
years (Taylor 1958). Earlier Jack (1913) had reported that a braconid larval
parasitoid was ineffective in controlling bean fly although it was bred freely
from O. phaseoli late in the season.