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

1996). Although the link between “bottom-up” prey resources in the habitat and predator
abundance has been demonstrated in some systems, its importance to the biological control
of herbivores has not been well established (Mathews et al., 2004 and references in). The
observed increase in oribatid mites did not correlated positively with their potential carabid
predators, at least in the short term. However, in our study the smaller species, which could
be potential mite predators, were collected at very low numbers, thus they could not forage
on this extra resource at the time of the experiment.
The results, especially for predators, warrants further investigation because the broad-
spectrum insecticides will continue playing a role in the D. pallens control. Anthropogenic
pastures are considered relatively impoverished compared to more natural habitats, but they
contribute to the biodiversity of Southern Chilean ecosystems because of their extension
and patchy landscape.
Use of microbial pesticides for integrated pest management (IPM) has increased in recent
years in part because of the low selectivity of conventional insecticides. Biopesticides
based on B. bassiana have characteristics readily amenable to accomplish IPM
requirements, but concerns for the environment has resulted in greater scrutiny of both old
and new plant protection products (Solomon and Giesy, 2001), including B. bassiana.
Before widespread use of these fungi can be advocated, a comprehensive assessment of
their impact on the non-target species are needed (Parker et al., 1997). An assessment of the
ecological risks of B. bassiana should include a comparison with the risks of conventional
control methods, as it was performed in this study. On the other hand, the risk and hazard
assessment process is completed just when the different stages (hazard identification,
exposure assessment, effects assessment, risk characterization and risk management) are
accomplished (Römbke and Moltmann, 1996). Therefore, more detailed knowledge of
invertebrate community dynamics on Chilean pastures is needed to enhance pest control
and to ensure that this new technology is safer than the current techniques in use.
Finally, results of this study supported the findings reported on early literature, which
showed that the use of B. bassiana spores at field do not pose a significant hazard for any
recorded non-target guild or taxon, while the use of a broad-spectrum insecticide like
lambda-cyhalothrin severely disrupted the predator assemblage. The ecological
consequences of this disruption can not be anticipated by a short-term study like this, but
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