Biofungicides from plants are a possibility for the biocontrol of fungal diseases, as chemical products may be harmful to the environment and humans. Strawberry is one of the many plants infected by grey mould (Botrytis cinerea), and innovative methods of biocontrol against B. cinerea are under investigation. Clove (Syzygium aromaticum L.) and cinnamon (Cinnamomum cassia L.) accumulate natural compounds, such as eugenol and cinnamaldehyde, which provide antimicrobial and antifungal properties; thus, extracts of these plants could be possibly used as biofungicides. During this study, the inhibition of B. cinerea by clove and cinnamon extracts was evaluated in vitro on Petri plates and detached strawberry leaves; additionally, the chemical composition of volatiles was identified. Clove extract consisted of 52.88% eugenol, and cinnamon consisted of 74.67% cinnamaldehyde. The efficacy of the extracts on detached strawberry leaves showed that 12 mL L−1 concentration of clove extract was effective in suppressing the grey mould infection. Clove and cinnamon extracts showed an equal ability to inhibit B. cinerea on Petri plates. However, the results of the detached strawberry leaves assay showed that clove extract was more effective as a biocontrol product. Overall, clove extract expressed a high potential for application in biofungicides formulations.

Sustainable plant protection can be applied on apples against fungal pathogens such as Botrytis cinerea (which is responsible for gray mold)—a significant global postharvest disease. This pathogen can affect a wide range of hosts; and fruits may have variable susceptibilities to B. cinerea from different plant hosts. New possibilities to control gray mold in food production are under demand due to the emergence of resistance against antifungal agents in fungal pathogens. Cinnamon, pimento, and laurel extracts were previously assessed for antifungal activities under in vitro conditions and were found to have the potential to be effective against postharvest gray mold. Therefore, this study aimed to investigate the antifungal activity of cinnamon, pimento, and laurel extracts in vitro and against postharvest gray mold on apples to determine the susceptibility of apple fruits to B. cinerea from different plant hosts, and to analyze the chemical composition of the extracts. Apples (cv. “Connell Red”) were treated with different concentrations of extracts and inoculated with B. cinerea isolates from apple and strawberry followed by evaluation of in vitro antifungal activity. The results reveal that most of the concentrations of the extracts that were investigated were not efficient enough when assessed in the postharvest assay, despite having demonstrated a high in vitro antifungal effect. Apples were less susceptible to B. cinerea isolated from strawberry. To conclude, cinnamon extract was found to be the most effective against apple gray mold; however, higher concentrations of the extracts are required for the efficient inhibition of B. cinerea in fruits during storage.

Essential oils and plant extracts of the rosemary (Rosmarinus officinalis L.), bay-laurel (Laurus nobilis L.) and clove (Syzygium aromaticum L.) contain various valuable compounds that provide antimicrobial and antifungal properties. As a result, they have the potential to be used in plant-pathogen control. Botrytis cinerea is one of the main strawberry pathogens, which infects plants during various stages of growth. The study aimed to evaluate the efficacy of plant extracts and essential oils of rosemary, bay-laurel and clove, and their mixtures against B. cinerea in vitro. Rosemary, bay-laurel and clove extracts and essential oils were separately and in combinations mixed with potato dextrose agar media at different concentrations. Fractional inhibition concentration (FIC) indexes were calculated for the mixtures to determine synergistic, additive or antagonistic effects of the combinations of the investigated plant extracts and essential oils. Results of the experiment showed that clove extract had the highest inhibition (100%) of B. cinerea, and rosemary essential oil had the lowest inhibition (31.91%). The mixtures, which managed to fully inhibit the growth of B. cinerea, were clove extract + clove essential oil, bay-laurel extract + clove essential oil and rosemary extract + clove essential oil. Synergy was found between bay-laurel extract and clove essential oil, and rosemary extract and essential oil, the FIC indexes were equal to 0.75 for both mixtures. The mixture of bay-laurel extract and bay-laurel essential oil was antagonistic as the FIC index was 2.5.

The Colletotrichum spp. is a significant strawberry pathogen causing yield losses of up to 50%. The most common method to control plant diseases is through the use of chemical fungicides. The findings of plants antimicrobial activities, low toxicity, and biodegradability of essential oils (EO), make them suitable for biological protection against fungal pathogens. The aim is to evaluate the inhibition of Colletotrichum acutatum by thyme, sage, and peppermint EO in vitro on detached strawberry leaves and determine EO chemical composition. Our results revealed that the dominant compound of thyme was thymol 41.35%, peppermint: menthone 44.56%, sage: α,β-thujone 34.45%, and camphor: 20.46%. Thyme EO inhibited C. acutatum completely above 200 μL L−1 concentration in vitro. Peppermint and sage EO reduced mycelial growth of C. acutatum. In addition, in vitro, results are promising for biological control. The detached strawberry leaves experiments showed that disease reduction 4 days after inoculation was 15.8% at 1000 μL L−1 of peppermint EO and 5.3% at 800 μL L−1 of thyme compared with control. Our findings could potentially help to manage C. acutatum; however, the detached strawberry leaves assay showed that EO efficacy was relatively low on tested concentrations and should be increased.

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