The use of synthetic fungicides to control fungal diseases has growing limitations due to eco-toxicological risks. Therefore, it is necessary to replace or integrate high risk chemicals with safer tools for human health and environment. Consequently, research on the selection, evaluation, characterization, and use of biocontrol agents (BCAs) has consistently increased in the last decades. BCA formulates, particularly in some countries, are still scarce in coping with the growing demand for their use in sustainable agricultural management. To foster development and utilization of new effective bioformulates, there is a need to optimize BCA activity, to share knowledge on their formulation processes and to simplify the registration procedures. Studies based on new molecular tools can significantly contribute to achieve such objectives. The present review provides the state of the art on biocontrol of fungal plant diseases with special emphasis on (i) features of the most studied BCAs; (ii) key strategies to optimize selection and use of BCAs (iii); mechanisms of action of the main BCAs; (iv) molecular tools and metagenomic studies in the selection and use of BCAs; (v) main issues and constraints in the registration and commercialization of BCAs, and (vi) perspectives in the biocontrol of fungal plant diseases.

Fusaric acid (FA) is one of the first secondary metabolites isolated from phytopathogenic fungi belonging to the genus Fusarium. This molecule exerts a toxic effect on plants, rhizobacteria, fungi and animals, and it plays a crucial role in both plant and animal pathogenesis. In plants, metal chelation by FA is considered one of the possible mechanisms of action. Here, we evaluated the effect of different nitrogen sources, iron content, extracellular pH and cellular signalling pathways on the production of FA siderophores by the pathogen Fusarium oxysporum (Fol). Our results show that the nitrogen source affects iron chelating activity and FA production. Moreover, alkaline pH and iron limitation boost FA production, while acidic pH and iron sufficiency repress it independent of the nitrogen source. FA production is also positively regulated by the cell wall integrity (CWI) mitogen-activated protein kinase (MAPK) pathway and inhibited by the iron homeostasis transcriptional regulator HapX. Collectively, this study demonstrates that factors promoting virulence (i.e., alkaline pH, low iron availability, poor nitrogen sources and CWI MAPK signalling) are also associated with increased FA production in Fol. The obtained new insights on FA biosynthesis regulation can be used to prevent both Fol infection potential and toxin contamination.

Brown rot caused by Monilinia spp. is the main disease of stone fruits. Our research aimed to identify an appropriate strategy to control plum brown rot and reduce fungicides residues in fruit through targeted application of the biocontrol agents (BCAs) Papiliotrema terrestris and Bacillus subtilis, alone or in combination with synthetic fungicides. The following treatments were evaluated: Biological (BIO1, BIO2), Integrated (INT1, INT2, INT3), and Combined (COMB), all compared with Chemical strategy. Five key treatments (seven for BIO2) were performed in the crucial phenological stages for the disease cycle: INT1, INT2, and INT3 approaches consisted, from the beginning of the season, of one, two, or three treatments, respectively, alternately with boscalid or cyprodinil followed by applications of BCA until the fruit harvest. After harvest, plums were subjected to an additional treatment with the two BCAs and the fruits were stored at 20 °C for 15 days. The results obtained by applying our BCA PT22AV, revealed, in the field and in postharvest, the highest level of disease protection with management strategies BIO2 (94.8–97.2% in field; 65–84% in postharvest) and INT3 (95.5–97% in field and 63% to 91% in postharvest). The level of fungicide residues in fruit was zero in BIO strategies and lower in INT strategies as compared to chemical strategy.

Management of Xylella fastidiosa subsp. pauca (Xfp) presents significant challenges because of the lack of genetic resistance in major crops, pathogen variability and resistance development against the main antimicrobial compounds, and the lack of effective chemical compounds for control. Traditional bactericides in the EU are restricted, and copper-based products are increasingly limited because of environmental impacts. In this study, the antibacterial side effects of some commercial fertilizers against Xfp were evaluated. These products, containing metal ions (mainly copper and/or zinc) complexed with phosphites and bioavailable silicon, show antimicrobial and bactericidal activities in vitro, which suggest their possible use to control the pathogen, as well as enhanced plant resistance to biotic and abiotic stresses. Greenhouse and open field trials showed that they can significantly reduce disease severity and pathogen population, thus improving fruit yield. The integrated pest and disease management strategy, which combines these treatments with agronomic and phytosanitary vector-control measures, leads to a reduction of disease symptoms in treated plants compared with untreated ones. These findings highlight the potential of systemic fertilizers to mitigate Xfp symptoms by providing antimicrobial collateral effects and probably enhance plant defenses, since similar compounds are known to be plant defense inducers in other pathosystems. Therefore, these products offer a sustainable solution for managing plant pathogenic bacteria and improving crop health and yield. This approach is crucial for the sustainability of olive production in Xf-affected areas. However, further research is needed to optimize these strategies for long-term effectiveness under field conditions. Overall, the results emphasize the value of the collateral effects of some mineral fertilizers in a comprehensive strategy aimed at mitigating the symptoms of Xfp and safeguarding the agricultural productivity as well as the invaluable heritage of centuries-old Apulian olive trees. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Plasmopara viticola, the causal agent of grapevine downy mildew, is one of the most important pathogens affecting vineyards worldwide. In Italy, the 2023 growing season was among the most critical in recent years, with severe downy mildew outbreaks favored by exceptionally conducive climatic conditions. Proper management minimizes yield losses and reduces reliance on synthetic and copper-based fungicides, thereby mitigating risks for the environment and consumer health. Our research aimed to develop an effective and sustainable biological control strategy based on the application of a beneficial microorganism combined with natural compounds, while reducing copper inputs. Over two years, different biological and integrated control strategies were compared with conventional programs based on synthetic anti-downy mildew fungicides. Overall, the results highlighted the importance of: (i) a preventive approach, involving early-season applications targeting primary inoculum and initial infections; and (ii) an integrated strategy, combining different anti-downy mildew formulations with multiple modes of action. Across two years of field trials, the greatest reduction in disease incidence was achieved with integrated control strategies in which the bioformulate YSY^®, based on the beneficial yeast PT22AV, was applied early in the season, in combination with other commercial formulations based on copper and plant extracts.