Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

104 Biological Control of Insect Pests: Southeast Asian Prospects
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pseudostems and in moist soil below banana mulch. Pupation occurs in the
soil. Total development time averages 46 days and adults live an average of
142 days (Koppenhšfer 1994).
Although weevils, as a group, seem to be poor candidates for biological
control, the establishment of Plaesius javanus and P. laevigatus in Fiji
appears to have reduced the pest status of Cosmopolites sordidus there.
Introductions of P. javanus (Table 4.5.2) have resulted in successful
establishment (but often not at the first attempt) in Cook Is, French
Polynesia, Jamaica, Marianas, Mauritius, New Caledonia, Samoa and
Trinidad, but no information is available on the effects it has produced.
Introductions have been unsuccessful in Australia, Cameroon, Dominica,
Honduras, Mauritius, Mexico, Puerto Rico, Seychelles, St Lucia, St Vincent,
Taiwan, Tanzania, Tonga and Uganda (Bartlett 1937; Miwa 1938; Clausen
1978). Based on his observation and that of others, Koppenhšfer (1993a,b,
Koppenhšfer and Schmutterer 1993) considered that the biology of
P. javanus does not enable it to have any greater effect and that studies are
necessary of the potential impact of proposed predator species before
release. Two other predators have been established, one in Australia and one
in Jamaica and St Vincent, but seemingly without much effect.
If the beneficial effects of P. javanus (and P. laevigatus) in Fiji can be
confirmed, it may be worth renewing efforts to establish them in other
countries where C. sordidus is a major pest. Otherwise, resources available
for biological control might be better deployed searching for, and
evaluating, other natural enemies.
It is possible that entomopathogenic nematodes (CSIRO 1993;
Treverrow and Bedding 1993a) or fungi may hold some promise as
biological pesticides. Nematodes generally have far less capability for selfperpetuation
and dispersal in the environment than imported arthropod
enemies, but they can be highly effective. However, in many tropical
countries where bananas are a major staple food the distribution and
application of mass-produced biological control agents, such as nematodes
or fungi, is often impracticable because of storage and transport problems
and lack of suitable equipment for application. In addition, like insecticides,
they may be too costly for subsistence farmers who constitute the majority of
banana producers. Even if it only leads to a partial (but still significant)
reduction in pest status, classical biological control is, under these
circumstances, a particularly appropriate approach to reduce losses.