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

same percentage of mortality on larva than the insecticide lambda-cyhalothrin (>80% of
efficacy).
Like any pest control technology, B. bassiana may present a risk to non-target species,
including the natural enemy community. Laboratory tests have indicated some level of
acute adverse effects on a suite of individual non-target organisms (Traugott et al., 2000;
Danfa and van der Valk, 1999), while field studies have reported minor or non existent
deleterious effects of Beauveria sp. spores on non-target species (Riedel and Steenberg,
1998; Lynch and Thomas, 2000).
On the other hand, few laboratory and field studies have addressed the non-target effects of
insecticides currently in use against D. pallens and less studies have been conducted at the
supra-species level. We choose two sampling methods (soil cores and pitfall sampling) and
a relatively new tool based on ordination called principal response curve (PRC), to evaluate
the predator, herbivore and decomposer guild responses to D. pallens control. Analysis of
PRC was especially designed for mesocosms experiments (van den Brink and ter Braak,
1999) and has been extended to other fields in recent years (Naranjo, 2005; Naranjo and
Akey, 2005; Naranjo et al., 2004; Candolfi et al., 2004; Dively and Rose, 2002).
We used this approach because the experiments on non-target effects produce large data
sets on which standard univariate statistical methods do not perform well in all cases,
mainly because the data often are over-dispersed and a large number of sequential zeroes
are present. Multivariate analysis may be used to describe the effect of chemical stress at
the assemblage level (van den Brink and ter Braak, 1999) and the PRC displays, in a single
graph, the treatment effects over time and allows to determinate the statistical significance
of the effects by Monte Carlo (MC) permutation testing (van den Brink and ter Braak,
1998).
The aim of this study was to compare the short-term effects of biological and chemical
control of D. pallens on several guilds (predators, herbivores and decomposers). For this
purpose, we carried out an experiment which we assessed the activity/abundance of these
guilds before and after a single application of the B. bassiana isolate B-931 and the
synthetic insecticide lambda-cyhalothrin.
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