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

explanation than no toxicity of the insecticide, considering significant effects of lambda-
cyhalothrin were detected twice in the following sampling dates and that lambda-
cyhalothrin toxicity to carabids is well documented in literature (Huusela-Veistola, 1996;
Koss et al., 2005; Prasifka et al., 2005; White et al., 1990), though the response is always
species-specific.
F. nebroides showed a consistent response across the study. Activity density in the lambda-
cyhalothrin plots was lower than control in the three post sampling dates, although the
differences were significant at α= 0.05 only at the beginning and at the end of the sampling
period, while the response at the intermediate sampling date was not statistically significant
(p=0.29). Other carabids with comparable body size to F. nebroides can move several
meters per day (Thacker and Dixon, 1996), but insecticide plots did not recover the pre-
treatment populations levels at any sampling date.
The negative effect of lambda-cyhalothrin on F. aerea population was evident two months
after spray, but not one month after spraying. Absolute numbers increased with time in all
treatments, but the increase was much more marked in the control plots than in insecticide
plots, in the last sampling date. This species overwinters as adult, thus the increase should
be attributed to adults moving from no treated areas to plots and not to new cohorts of
adults from larvae that complete their cycle.
The absence of barriers, the presence of migrant sources and the plot size would have
facilitated (or at least no make more difficult) the re-colonization of treated plots by F.
nebroides and F. aerea. The reasons why the re-colonization was not accomplished as
expected are not clear. If the insecticide had persisted in the treated plots, direct mortality
or repellence could be acted on beetles, but lambda-cyhalothrin has been reported to persist
less than 2 weeks in field (Hill and Inaba, 1991; Mathirajan et al., 2000). In addition,
lambda-cyhalothrin decreases when temperature increases (Huusela-Veistola, 1996) and
temperature at November-December in the region (late spring and early summer) are
typically higher than October (mid spring).
Several authors have reported that carabids do control lepidopteran pests (French et al.
2004; Frank and Shrewsbury, 2004; Toft and Bilde, 2002). The carabid species active at the
sampling period likely would not be predators of Dalaca sp. because of their body size. It is
generally noted a positive correlation between the size of the beetles and the size of the
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