Aplicação de fungicidas químicos e biofungicidas no manejo de doenças da soja em Katuete – Paraguai

Abstract

Agricultural inputs can reduce losses caused by pests and diseases. However, the indiscriminate use of chemical fungicides increases the selection pressure for fungicide-resistant pathogens. In this context, combining different active ingredients with biological fungicides may contribute to reducing disease severity and maintaining soybean yield. This study aimed to evaluate the association of biological and chemical fungicides in the integrated management of soybean diseases. Twelve treatments were evaluated, including eleven different management programs consisting of five spray applications. The programs included the systemic fungicides Score Flexi – triazole, Cripton Xpro – carboxamide/triazolinthione/strobilurin, Viovan – strobilurin/triazolinthione, Sphere Max – trifloxystrobin/cyproconazole, and Cypress – difenoconazole/cyproconazole; the multisite fungicide mancozeb; and the biological products Frontiercontrol – LABIM 40 microbial agent (CMRP 4489), seaweed extract, and BH. During the experiment, the following pathogens were detected: Colletotrichum truncatum, Cercospora kikuchii, Phakopsora pachyrhizi, Peronospora manshurica, and Cercospora sojina. For Cercospora leaf blight and Asian soybean rust, all management programs were effective, reducing disease severity by 50–60% and 91– 98%, respectively. For downy mildew, five management programs differed significantly from the untreated control, reducing disease severity by 56–87%. For anthracnose, most management programs showed a significant effect, with severity reductions ranging from 58% to 75%, while only two did not differ from the untreated control. These results demonstrate that management efficacy varied according to the pathogen and the composition of the management program. In addition, eight management programs resulted in an average yield increase of approximately 1,000 kg ha⁻¹ compared with the untreated control, indicating that integrated disease management contributed to crop protection and the maintenance of soybean yield potential.