INTEGRAÇÃO DO CONTROLE GENÉTICO, QUÍMICO E BIOLÓGICO NO MANEJO DE NEMATOIDES NA CULTURA DA SOJA (Glycine max L. Merril)

Abstract

Soybean (Glycine max L.) cultivation is among the main commodities for the world and Brazilian agricultural economy, and its productivity can be reduced by attacks from various nematode species. In order to understand the efficiency of different management strategies, this study aimed to evaluate the integration of genetic, chemical, and biological control in the management of root-knot nematodes (Meloidogyne javanica) and soybean cyst nematodes (Heterodera glycines) in soybean crop, highlighting the benefits of each control within integrated management. The trial was conducted in a commercial field in the western region of Bahia, in a randomized block design with a 2 x 15 factorial scheme (2 cultivars x 15 treatments), with four replications. The treatments considered were the active ingredients Fluopyram and Cyclobutrifluram, the fungal biological agents Purpureocillium lilacinus and Pochonia chlamydosporia, and the bacterium Bacillus velezensis. For soybean cultivars, a material without nematode resistance (Brasmax Olimpo IPRO) and one moderately resistant to M. incognita, H. glycines races 6, 9, 10, 14, and 14+, in addition to having resistance to race 3 (NEO 840 IPRO), were adopted. To estimate the effects of the treatments on the two soybean cultivars, phytotoxicity, plant stand, root length, shoot fresh weight (SFW), number of nematodes in the roots, number of nematodes in the soil, and crop productivity were evaluated. The active ingredient Fluopyram, applied via seed treatment, caused initial phytotoxicity in soybean crop, however, the symptoms were significantly reduced when combined with biological control. This phytotoxicity did not affect the development of the soybean shoots. The evaluated cultivars showed genetic differences for quantitative characteristics, with the Brasmax Olimpo IPRO cultivar presenting a higher initial stand and a more developed root system, while the NEO 840 IPRO cultivar showed better performance in the shoot fresh mass variable at 75 DAE (days after emergence). The NEO 840 IPRO cultivar showed lower multiplication of M. javanica and H. glycines, impacting better productivity. Genetic control proved to be the basis of management, being the main factor responsible for the reduction in the nematode population in the trial conducted. However, in the absence of resistance, all treatments evaluated promoted a reduction in the nematode population compared to the control at 75 DAE. The isolated application of chemical or biological products provided a numerical increase in productivity of up to 22.87% in the NEO 840 IPRO cultivar and up to 86.35% in the Brasmax Olimpo IPRO cultivar. The integration of biological and chemical management provided greater numerical increases in productivity compared to the isolated application of each method, with the combination of Bacillus velezensis, applied in seed treatment, and Fluopyram, via planting furrow, providing a numerical increase of 49.51% in the NEO 840 IPRO cultivar, and the combination of Bacillus velezensis and Cyclobutrifluram, applied in seed treatment, providing a numerical increase of 114.48% in the Brasmax Olimpo IPRO cultivar. Integrated management, combining genetic resistance, chemical and biological nematicides, showed the greatest productivity gains for soybean cultivation.