Efeito de bioagentes, tratamento quimico das sementes e descompactação do solo no manejo da podridão vermelha da raiz em soja.

Abstract

The expansion of soybean cultivation in Brazil, combined with inadequate phytosanitary practices, has favored the spread of soil-borne diseases caused by fungi such as Fusarium spp. and plant-parasitic nematodes, which form pathogen complexes with still poorly understood interactions. In light of the increasing incidence of Fusarium diseases on soybeans and the need for integrated management strategies for root diseases, this study aimed to evaluate the management of red root rot in soybean using bioagents and complementary agronomic practices, proposing sustainable solutions for the crop. The research was carried out under experimental field during the 2023/2024 and 2024/2025 growing seasons, with the cultivar 80I82RSF IPRO (Brasmax Olimpo IPRO). The variables consisted of the disease severity index (DSI), nematode population density, crop stand, and yield. In the first chapter, red root rot and nematode management were assessed in a randomized block design with a 2 × 3 × 2 factorial arrangement, considering soil management (compacted and decompacted), application of Trichoderma harzianum BRM 29600 (on seeds, in-furrow, and untreated control), and seed chemical treatment (with and without fungicide). The results submitted to ANOVA indicated that in the 2023/2024, the lowest DSI were observed in treatments with infurrow spraying of T. harzianum on compacted soil. Trichoderma harzianum BRM 29600 favored higher yield, especially when combined with chemical seed treatment. No differences were observed in 2024/2025. Principal component analysis (PCA) revealed an inverse correlation between DSI and yield, highlighting the effectiveness of biological control. In the following season, DSI exceeded 65% in all treatments, but yield was higher than in the previous year due to more favorable climatic conditions. The combination of biocontrol, chemical treatment, and proper soil preparation proved promising for disease mitigation. The second chapter evaluated nine isolates of Trichoderma spp. and two entomopathogenic fungi (Metarhizium anisopliae and Cordyceps javanica) applied to seeds. The 2023/2024 results indicated increased yield and reduced DSI with the use of bioagents, particularly the de Trichoderma sp. BRM29675 isolate. In 2024/2025, DSI increased and treatment differences were not significant, although overall yield exceeded 5000 kg/ha. The study reinforces the importance of integrated management to manage soybean root diseases, and evidences the impact of environmental conditions on crop yield, disease severity and treatment efficacy.