Risco bioecológico do milho transgênico em insetos não-alvo do sistema de produção

Abstract

Transgenic plants resistant to insects, or Bt plants, are resistant to target pests, leading to a decreased use of insecticides. Studies of risk assessment of Bt crops on non-target organisms are important tools for this technology continue bringing economic benefits without affecting biodiversity. Therefore, the aim of this thesis was to investigate the bioecological risk of Bt maize production system on non-target insects. For this, we conducted a bioassay and a field study. 1. Bioassay: Was conducted in a laboratory at University of Minnesota, Saint Paul, USA. We conducted choice tests of food preference to determine if the predator Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) shows any preference between Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) fed Bt maize leaves (MON-810) or non-Bt maize. The bioassay was conducted in Petri dishes. Each predators (larvae and adults) received pray which fed Bt or non-Bt maize leaves for 24, 48 and 72 h. Both stages of the predator consumed the caterpillars that were offered. In all combinations of predator and prey age, the number of each type of prey consumed did not differ statistically. The ELISA test confirmed the presence of Cry1Ab in leaf tissue and S. frugiperda, while concentrations H. axyridis third instars and adults were very low. Based on the data obtained it appears that H. axyridis is a potential predator of S. frugiperda and has no preference between prey fed leaves from Bt corn and non-Bt. 2. Field Study: Was conducted in the State of Mato Grosso do Sul, Brazil. This study aimed to determine whether there are differences in composition and species richness of ants and beetles on soil production system of Bt and non-Bt maize, in two growing seasons (2009 to 2011), summer and winter, in the Midwest Brazil. This research was developed in the areas of production of Bt and non-Bt maize. We studied six areas of maize production on summer, and seven areas in winter periods. The insects were collected using pitfall traps. Data were analyzed using faunistics indices of richness and species diversity. Nevertheless, there was no statistically significant difference on richness and species diversity between production systems of Bt and non-Bt maize. In the winter crop season, occurred some unique species, as well as other species occurred exclusively in the summer. Furthermore, there was greater richness and species diversity of ants and beetles during periods of summer crops. Based on the results of this research, we can say that there was no bioecological impact of the production system of Bt maize.