Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

194 Biological Control of Insect Pests: Southeast Asian Prospects
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It is not clear how many of the natural enemies are sufficiently host specific
to be confidently transferred as biological control agents although, where
alternative hosts are known, these are also pests. Thus, Eriborus
argenteopilosus has a wide host range, including Condica (= Prospalta)
capensis, which attacks safflower and sunflower, Helicoverpa armigera,
and Spodoptera exigua (Tewari and Sardana 1987a,b). The ichneumonid
Pristomerus testaceus has been bred from the brinjal stem-borer Euzophera
ferticella (Ayyar 1927). It is not known whether the ichneumonid
Phanerotoma sp. nr hindecasisella is a distinct species. True
P. hindecasisella has been reported from several lepidopterous families in
India or Sri Lanka: Gelechiidae (Dichomeris eridantis), Noctuidae (Earias
insulana), Pyralidae (Eutectona (= Pyrausta) macheralis, Hendecasis
duplifascialis, Maruca vitrata (= M. testulalis), Nephopterix rhodobasalis,
Syllepte derogata) and Tortricidae (Leguminivora (= Cydia) ptychora)
(Thompson 1953; Fellowes and Amarasena 1977; Kumar et al. 1980;
Tewari and Moorthy 1984).
Bracon greeni is best known as a primary ectoparasitoid of the
lepidopterous lac predator Eublemma amabilis (Noctuidae) and has not been
reported to parasitise any other host in nature. However, under laboratory
conditions, it was successfully reared on L. orbonalis (Venkatraman et al.
1948).
Although entomopathogenic nematodes have not been recorded
attacking L. orbonalis in the field, Steinernema (=Neoaplectana)
carpocapsae (DD136 strain) produced 73.3% mortality of larvae in the
laboratory in 72 hours (Singh and Bardhan 1974).
The weight of evidence suggests that L. orbonalis originated in India and
spread into Southeast Asia. It is most surprising that it has only
comparatively recently become a pest Ñ and a serious one Ñ in the
Philippines which, in 1990, had 16 000ha under egg plant and produced
113 000 tonnes, second only to Indonesia in production in Southeast Asia
(FAO 1991). In view of the steady spread around the world of so many other
pests it is also surprising that Australia, the Pacific, the Americas and Europe
are still free from L. orbonalis.
It might well be assumed that not all of its natural enemies in India have
accompanied it during its spread. However, reports of high damage levels to
susceptible egg plant cultivars in India do not provide much confidence that
the natural enemies there are particularly effective, unless their efficacy is,
perhaps, reduced by insecticide applications or so-far-unreported
hyperparasitoids.