EFICIÊNCIA DE NEMATICIDAS QUÍMICOS, BIONEMATICIDAS E EXTRATOS VEGETAIS NO CONTROLE DE Pratylenchus brachyurus EM SOJA

Abstract

The comparative evaluation of different control strategies allows the soybean farmers to have parameters to determine the most effective management and with lower cost, ensuring the profitability of the crop. Chemical nematicides, despite having a high acquisition cost, are efficient for the population reduction of Pratylenchus brachyurus, mainly in the initial phase of the plant, which benefits the initial harvesting of the crop. Bionematicides are less costly biological products with good efficiency, but they need the establishment of the biological agent in the environment to start the reductive effect in the population. The use of antagonistic plants in the form of plant extracts is not widespread in soybean culture, however the study of the efficiency of nematicidal substances from their metabolism will lead to the achievement of new management strategies. In this sense, the objective of this work was to comparatively evaluate the action of chemical nematicides, bionematicides and plant extracts of Senna obtusifolia and neem in the control of P. brachyurus in soybean crop. The experiment was conducted in a commercial field in Vilhena-RO, granted by rural producer Adair Menegol. This area is naturally infested with Meloidogyne sp., Helicotylenchus dihystera and P. brachyurus, during the 2018/2019 harvest. The treatments adopted were abamectin (125 mL / 100 kg of seeds), imidacloprid + thiodicarb (700 mL / 100 kg of seeds), Bacillus subtilis (4 mL pc / kg of seeds), Purpureocilliu lilacinus (0.25 kg pc / 100 kg seeds), Neem cake (429 kg / ha), Neem oil (457 mL / 100 kg of seeds), ethyl Extract of S. obtusifolia (660 mL at 20% / 100 kg of seeds) and the control. The evaluations were performed at 30, 60 and 90 days after emergence, where the nematological and plant development variables were evaluated. In software R, the data were submitted to the normality and homogeneity test, and the treatment means were compared using the Scott-Knott and Friedman tests. Abamectin provided a significant reduction of 85.19% in the population of P. brachyurus at 30 DAE. The application of imidacloprid + thiodicarb also conferred a reducing effect on the population linked to the greater development of the plant at 30 and 90 days after emergence (DAE) of the plant. The biological products did not obtain expressive results. The neem cake promoted greater plant development associated with a reduction of 24.86%, 47.69% and 83.02% of the nematode population, respectively at 30, 60 and 90 DAE. The use of neem oil had a similar behavior to neem cake, but its efficiency was reduced to 90 DAE. The ethyl Extract of S. obtusifolia provided greater plant development and population reduction only in the first evaluation. However, this treatment resulted in greater productivity with a significant increase of 494.44 kg ha-1 in relation to the control. The treatments with ethyl Extract of S. obtusifolia and imidacloprido + tiodicarb promoted greater development of the culture associated with greater productivity. Therefore, abamectin is recommended in areas of high infestation to immediately reduce the population of P. brachyurus. The treatments with ethyl Extract of S. obtusifolia and imidacloprido + thiodicarb presented similar behavior and can be well used in soybean culture.