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

1994; Nowak et al., 2001; Tillman and Mulrooney, 2000; van den Berg et al., 1998), as
well as other organisms like fish and non-target herbivores. These studies reported transient
decreases in non-target numbers, specifically predators and parasitoids, immediately after
λ-cyhalothrin treatment, but numbers recovered within a short period (usually 10-15 days).
Our results suggest more long-term effects because the adverse effects of the insecticide
were present for at least 40 days after treatment despite of the absence of barriers to
movement and the fact that plots were surrounded by untreated grassland providing large
sources of migrants. On the other hand, we consider that development stage of the
invertebrates could explain, at least partially, these results: in the winter experiment, many
individuals were immature and would have lower mobility than adults, therefore the
recovery time in this season may be longer than in the spring or summer, seasons in which
the most of the mentioned studies were conducted.
The insecticide affected all community metrics in winter, while it affected diversity,
evenness and dominance but not species richness in spring. The latter result must be
interpreted cautiously, because the period between spraying and sampling in the spring
experiment could have been long enough to allow migrants move from surrounded area to
plots. Therefore, a negative impact of insecticide in the spring species richness could be
masked by movement of these migrants.
In relation to new emerging technologies, for example narrow spectrum insecticides, B.
bassiana based biopesticides could play an important role because Chilean daily and beef
industry can not compete with the rest of South America. Instead, it is focused in high-
profit market niches such as organic or naturally raised cattle, where these new pesticides
would not be allowed, in spite of they have better properties than the broad-spectrum
insecticides currently used. In addition, if an IPM program is implemented for D. pallens
control, many alternatives will be needed to design an robust and sustainable program.
Linking between biodiversity and ecosystem functioning is accumulating support, but the
issue remains unresolved (Ehrlich and Wilson, 1991). This relationship has been
hypothesized to be linear (the rivet hypothesis, Ehrlich and Ehrlich, 1981), asymptotic (the
redundancy hypothesis; Walker, 1992) or idiosyncratic (Lawton, 1994). Despite of these
different theories, it can be argued that some level of biological diversity is necessary to
maintain ecological function and resilience (Spratt 1997) but unfortunately, incomplete
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