Abstract

ZENNER DE POLANIA, Ingeborg  and  ALVAREZ ALCARAZ, Guillermo. ANALYSIS OF THE INFLUENCE ON THE MAIN BENEFICIAL FAUNA BY TWO TRANSGENIC CULTIVARS, COTTON AND CORN, AT EL ESPINAL (TOLIMA). rev.udcaactual.divulg.cient. [online]. 2008, vol.11, n.1, pp.133-142. ISSN 0123-4226.

SUMMARY During three years, field observations and laboratory studies were carried out in order to evaluate, in a general manner, the effect, direct or indirect, that cotton and maize Bt cultivars could have on the natural enemies of the two main insect pests of these plants, Heliothis virescens and Spodoptera frugiperda. Predator and parasitoid populations were analyzed, with the expected result: the Bt toxins, Cry1Ac and Cry1Ab incorporated, respectively, in the cotton cultivar Bollgard® and the maize hybrid Yieldgard® do not exercise a direct effect on the populations of the studied beneficial fauna. The decrease of their populations in commercial fields of both transgenic and conventional varieties is attributed to a decrease of prey and hosts, due to insecticidal applications against pests not controlled by the toxins and the control of H. virescens and S. frugiperda by the cotton and maize Bt cultivars, respectively. It was concluded, that if the tendency of decrease of certain beneficial insects continues also in the conventional fields or "refuge fields", the coccinellid predator Cycloneda, and the parasitoids Cardiochiles and Meteorus should be considered endangered species, further more if in the future the second generation of transgenic cultivars will be implemented in the study area.

Keywords : Natural enemies; prey scarcity; host absence; insecticidal effect; Bt toxins.

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