Impacts of diverse chemical inputs on soybean disease dynamics and crop performance

Abstract

Late-season diseases (LSDs) are among the most significant biotic factors limiting soybean yield. Exploring alternative strategies for LSD management yields social, environmental, and economic benefits. This study aimed to evaluate the effectiveness of carboxamide-based fungicide applications in controlling soybean LSDs. The experiment was conducted in Pinhalzinho, São Paulo, Brazil, using a randomized complete block design (RCBD) with five treatments and four replicates, totaling 20 experimental units. Treatments included four fungicide management strategies involving carboxamides and one untreated control. Fungicide applications began 27 days after sowing (DAS) and were repeated every 15 days following disease detection. Evaluated variables included disease severity, area under the disease progress curve (AUDPC), number of pods per plant, number of seeds per pod, grain yield (kg ha⁻¹), and thousand-grain weight. Data were subjected to analysis of variance (ANOVA) and treatment means were compared using Tukey’s test (p < 0.05). Results showed that treatments 2 and 4 were most effective in reducing the progression of target spot and brown spot, respectively. In contrast, treatment 1 exhibited the highest severity of leaf blight. Treatment 2 achieved the highest yield (4974.12 kg ha⁻¹), though yield differences among treatments were not statistically significant. Thousand-grain weight did not differ significantly across treatments, with treatment 3 showing the highest average (185.62 g). Overall, the use of carboxamide-based fungicides contributed to reducing LSD severity and maintaining grain yield, indicating their viability as a tool within integrated disease management strategies.