Modern integrated farming systems encourage the search for alternative (non-chemical), highly effective methods of plant protection. In this study, the fungistatic effect of fennel essential oil (FEO) and hop essential oil (HEO) on fungal growth and their ability to treat Fusarium wilt was investigated. The study was conducted in vitro and in pot experiments. The severity of infection was assessed by disease index (DI), presence of Fusarium culmorum gDNA (qPCR) and anatomical analyses of infected plant tissue using an optical (OM) and scanning electron microscope (SEM). Laboratory analyses showed that FEO inhibits mycelial growth of Fusarium fungi (F. avenaceum, F. culmorum, F. equiseti, F. oxysporum, F. poae, F. solani, F. sporotrichioides, F. tricinctum), Botrytis cinerea and Cylindrocarpon destructans more effectively than HEO. FEO at a concentration of 2000 ppm completely inhibited the growth of F. culmorum, F. poae and B. cinerea. Both essential oils reduced the severity of Fusarium wilt caused by F. culmorum in pea plants (DI, OM, SEM). The qPCR shows that both essential oils are also able to reduce the synthesis of trichothecenes in the tissues of infected pea plants. The results of the study suggest that FEO and HEO represent a broad spectrum bio-fungicidal agent that can be applied directly to plants at a concentration of 500 ppm, greatly reducing the level of infection.

Winter barley (Hordeum vulgare L.) is an important crop used for feed, food, malting, and bioethanol production. Recent research indicates that the seed mycobiome significantly influences seed health and usability, affecting its potential applications. This study examined the fungal species present in seven barley cultivars grown under two agrotechnical regimes. Fungal species were classified according to their effects on seeds and plants, and biodiversity indices were calculated for each group. Enhanced agrotechnical practices increased yields and improved grain quality. Higher DON concentrations were observed in low-yield treatments. Mycological analysis revealed that field fungi, particularly Fusarium, dominated the grain mycobiome and were associated with infection and reduced seed quality. High Dominance (Y), Margalef, and Shannon–Wiener indices for quality-deteriorating fungi correlated with lower yields, while the Dominance index (λ) for these fungi was negatively correlated with grain protein content. The prevalence of specific fungi on seeds depends on storage conditions and fungal adaptations, which may result in complementary consortia. Understanding these interactions can support the development of effective seed storage strategies and inform material classification and future use decisions.