In U.S, Diaporthe species caused yield losses of 0.2 million metric tons in soybean in 2022. Quinone outside inhibitor fungicides carry high risk of fungicide resistance and may use for managing Diaporthe. In this study, isolates of D.aspalathi, D.caulivora and D.longicolla from 16 U.S. states were tested for their sensitivity to azoxystrobin. Significant effect of isolates (P<0.05) was observed on effective concentration at which mycelial growth was inhibited by 50% (EC50). The results showed the presence of sensitive Diaporthe isolates in soybean to azoxystrobin. Moreover, resistance to stem and seed infection by D.longicolla was evaluated in 39 soybean accessions. Significant effect of genotypes was observed on disease severity of stem and seed infection (P<0.05). Correlation between disease severity of stem and seed infection was non-significant. Results indicate defense mechanism against D.longicolla during stem and seed infection may differ. These findings indicate need to determine alternative fungicide chemistries and develop Diaporthe-resistant soybean varieties.