The Use of Clove and Rosemary Plant Extracts Against Colletotrichum acutatum and Botrytis cinerea

Horticulture and agriculture are facing the challenge of growing healthy and high-quality crops. Plant extracts are currently being widely investigated as an alternative means of plant protection. Interest in these measures has increased in order to reduce the use of chemical pesticides, environmental pollution, and adverse effects on human health. Also, due to the goals of the European Green Deal and the decreasing use of chemical pesticides, it has become essential to look for safer alternatives. The aim of this study was to investigate the inhibitory effect of plant extracts of clove (Syzygium aromaticum L.) and rosemary (Rosmarinus officinalis L.) against Colletotrichum acutatum and Botrytis cinerea plant pathogens and to evaluate fungal pathogens recovery after the exposure to the extract. The plant extracts (PEs) were obtained by subcritical CO2 extraction. The inhibitory effect of PEs was investigated in vitro at concentrations of 1200, 1600, 2000, 2400, 2800, and 3000 μL/L. Petri dishes were incubated at 25 ± 2 °C, and the mycelial growth of fungal pathogens was evaluated at 2, 4, and 7 days after inoculation (DAI). Reinoculation was then performed. The research showed that both plant extracts had an antifungal effect. However, clove PE was more effective. This allows us to say that plant-based measures can inhibit plant pathogens, but it is essential to determine the optimal concentrations and test them with different pathogens.