Controle biológico de fitonematoides na cultura da bananeira no Norte de Minas Gerais

Abstract

Banana is one of the most consumed fruit in the world, and it is produced mostly in tropical countries. The North of Minas Gerais is the third biggest banana producer in the country, following Vale da Ribeira in São Paulo and the North of Santa Catarina. Among the problems of the banana tree cultivation, there are the diseases caused by fungi, bacteria, viruses and nematodes. Nematodes are limiting factors of the productivity in many banana- producing regions where the species Radopholus similis, Helicotylenchus multicinctus, Pratylenchus coffeae, Meloidogyne spp. are found isolated or in population mixtures, and they interfere in the absorption and transportation of water and nutrients through the root system, and cause the tumbling of the plants and predispose them to the attack of other micro-organisms. The control of these phytonematodes is generally done using nematicides. This method has presented low efficiency due to the biodegradation problems, selection of resistant nematodes to the applied products, overuse, contamination of people and environment, and others. Among the alternatives to reduce the use of the pesticides, the biological control is one of the most discussed and can be defined as the control of one micro-organism from the direct action of the another micro-organism. The organisms engaged in the biological control are called antagonists. The bacteria Pasteuria penetrans, the fungus Pochonia chlamydosporia and the rhizobacteria Bacillus subtilis are promising agents of nematodes biological control, due to the prolonged survival of its spores in soil, harmless to the human being and to other animals, and the possible use with the cultural practices. The aim of this work was to evaluate the reduction of the nematodes population Meloidogyne sp., Helicotylenchus multicinctus, Radopholus similis e P. coffeae by the antagonist micro-organisms P. penetrans, P. chlamydosporia e B. subtilis, in areas of commercial cultivation of the banana tree, in Janaúba M.G. The experiment was conducted in two areas of commercial cultivation of the Prata-ană banana tree in (Musa spp., group AAB), irrigated by micro sprinkler, in Janaúba - M.G., from March 2009 to June 2010. The experimental design was entirely randomized. Samples were made before and after the treatment application. The samples consisted in the extraction of the soil and roots, in depth of 0 to 20cm and 10cm away from each of the four plants that composed the portion. The treatments consisted of T1: Pochonia chlamydosporia; T2: Bacillus subtilis; T3: Pasteuria penetrans; T4: P. chlamydosporia + B. subtilis; T5: P. chlamydosporia + P. penetrans; T6: P. penetrans + B. subtilis; T7: P. chlamydosporia + P. penetrans + B. subtilis; T8: Testemunha; T9: Carbofuran (Furadan) 350 SC. The average of the treatment was submitted to the nonparametric Statistics Kruskal Wallis. There was a reduction of the population at all genres of the nematodes after the application of the treatment, and over the experiment they did not increase again, denoting the efficiency of the agents from the biological control. The soil test of persistence in the fungus P. chlamydosporia performed after the end of the extractions proved that had been the dispersion of the fungus to all parcels of the two experimental areas.