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

Introduction.
In last decades, modern agriculture has implied ecosystem simplification, emphasis on
yield and intensive inputs, including pesticides (Banks, 2004). Endemic natural enemies of
insect pests represent a fundamental resource for maintaining pest population levels under
economic thresholds and maximizing their contribution to integrated pest management
(IPM) programs requires a detailed knowledge of their interactions with the target pest
(Furlong et al., 2004), population dynamics and response to disturbances.
Conservation biological control has been reinforced because of increasing awareness on
threats posed by alien biological control agents to native non-target species (Banks, 2004).
Ground beetles (Coleoptera: Carabidae) are one of the most common families of surface-
active arthropods in agricultural systems (Lövei and Sunderland, 1996; Cole et al., 2002),
while spiders are increasingly recognized as valuable biocontrol agents (Greenstone, 1999).
Several experimental studies have repeatedly demonstrated positive effects of generalist
predators on several crops, including corn (Clark et al., 1994), wheat (Dennis and Wratten,
1991) and oat (Helenius, 1990). Spiders meet several desirable characteristics as biological
control agents: they are relatively long lived, resistant to starvation and desiccation, good
dispersers and colonizers and predaceous at all stages of development (Greenstone, 1999).
On the other hand, carabids are abundant year roundly and they do not depend on only one
prey species. Many pesticides, including lambda-cyhalothrin, induce significant levels of
mortality in carabids and spiders (Epstein et al., 2000) thereby impacting their potential to
maintain pests in check.
In Southern Chile, the pasture yield is severely affected by the activity of Dalaca pallens
Blanchard, Dalaca chiliensis (Viette) and Dalaca variabilis larvae (Viette) (Lepidoptera:
Hepialidae). In general, D. pallens is the most abundant species in pastures and >200.000
ha per year are sprayed to control it. Insect growth regulators are used against early larval
stages of the pest, while broad spectrum pyrethroids such as lambda-cyhalothrin are
sprayed in Autumn to control neonate larvae and in Spring to control mature larvae.
Previous studies have shown that the fungus Beauveria bassiana applied at 10 12 spores per
ha has 80-100% of the lambda-cyhalothrin efficacy at controlling D. pallens larvae
(Cisternas, 2003).
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