Diversidad y control biológico de insectos - CyberTesis UACh ...

Introduction.
Declining diversity has raised concerns for continued provision of ecosystem services (e.g.
natural pest control). Intensification of agriculture and the subsequent simplification of
agroecosystems has often reduced biodiversity and can result in pest outbreaks (Swift et al.,
1996). Conservation of both natural enemies and non-target herbivores is desirable because
they play an essential role in whole community dynamics, and within the biocontrol
context, they may act as useful predators or as alternative prey when the target species is
scarce (Kenmore et al., 1984; Hardin et al., 1995)
Dalaca pallens (Blanchard 1852) (Lepidoptera: Hepialidae) is a native moth from South
America (Chile and Argentina) and the most important grassland pest in Southern Chile.
Adults emerge in late spring and drop eggs over pastures in flight. The larvae burrow a
vertical gallery in the soil and hide in it during daylight. At night, the larvae move to the
soil surface consuming leaves and culms. The larval stages develop over 6-8 months in soil,
causing extensive loss of forage during this time. About 10% of grassland area (ca.
200,000-300,000 ha) is sprayed against this insect every year, using conventional
insecticides such as insect growth regulators and pyrethroids. However, their use is seen as
undesirable for biological and economic reasons, therefore alternative strategies are needed
to manage this insect and reduce the reliance on chemical insecticides.
Beauveria bassiana Balsamo (Vuillemin) is under study as an efficient, environmentally-
friendly and economically competitive biopesticide for D. pallens control in Chile. One
potentially useful strain has been selected after conducting in vitro mortality assays and
field studies, which showed that the fungus caused mortality rates similar to the insecticide
cyhalothrin-lambda, when sprayed at 10 12 spores per ha (Cisternas et al., 2003). Farmers
have begun to adopt this new technology and the sprayed area increased from 20 ha in 2003
to 300 ha in 2005. However, effects on non-target invertebrates are unknown, as is this
treatment’s potential conflict with other biological control agents. Several studies have
reported side effects of Beauveria spp. on non-target arthropods, including carabid larvae
(Traugott et al., 2000), braconid and encyrtid wasps (Danfa and van der Valk, 1999) and
coccinellid predators (Jayanthi and Padmavathamma, 1996). Preliminary assays on the
Chilean species Allendia chilensis (Col.: Carabidae) and Phytoloema herrmanni (Col.:
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