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.

Colletotrichum spp. is a significant strawberry (Fragaria × ananassa Duch.) pathogen causing yield losses of up to 80%. Due to the changing agrometeorological conditions, pathogens are able to spread in cooler climate countries. Essential oils (EO), as one of the environmentally friendly plant protection products, can be used to control plant pathogens. They possess antibacterial and antifungal properties. Because of the low toxicity and biodegradability, EO can be used in plant protection against pathogens instead of chemical products. This study aimed to determine the pathogenicity of strawberry C. acutatum and evaluate five essential oils at different concentrations as potential bio-fungicides against strawberry anthracnose (Colletotrichum acutatum). The C. acutatum pathogenicity was evaluated on detached strawberry leaves. The inhibitory effect of five EO at 200, 400, 600, 800 and 1000 µl L -1 was evaluated in vitro, and at 800 and 1000 µl L -1 -on detached strawberry leaves. The cultivar 'Deluxe' was found to be the most susceptible to strawberry anthracnose, while 'Rumba' and 'Elegance' exhibited resistance. The results of Mentha piperita EO revealed its antifungal activity against C. acutatum. Meanwhile, Salvia officinalis EO had no influence. The Coriandrum sativum and Hyssopus officinalis EO slightly inhibited C. acutatum growth. The results of Thymus vulgaris EO assay in vitro demonstrated that it could be an effective biocontrol agent against strawberry anthracnose. EO inhibited the mycelial growth of C. acutatum in vitro; however, the results of the assay on detached strawberry leaves showed that the efficacy of EO was not sufficient and needed further research.

Previously, Colletotrichum spp. has been considered a warmer climate pathogen as these meteorological conditions are most optimal for its development. However, climate change is fostering the spread of plant disease and complicating the ability to predict meteorological conditions for disease development. This study aims to determine meteorological conditions for anthracnose development, evaluate the susceptibility of different strawberry cultivars and detect the distribution of strawberry pathogens in temperate climate conditions. The experiment was carried out in the Institute of Horticulture Lithuanian Research Centre for Agriculture and Forestry (LAMMC) in Lithuania during the 2018–2019 strawberry growing season. To evaluate the contamination levels (fungal and bacterial pathogens) of strawberry plant parts, soil and susceptibility to Colletotrichumacutatum, samples were collected at four different locations in Lithuania from eleven cultivars. The results revealed that Colletotrichum spp. was not equally prevalent in the soil at all strawberry farms tested. The evaluation indicated that strawberry leaves and stems were similarly contaminated with pathogenic fungi. The most frequently isolated fungi from the leaves and stems were Mycosphaerella spp., Alternaria spp., Fusarium spp., Colletotrichum spp., Phytophthora spp., and Botrytis spp. Our study confirmed that the response of cultivar susceptibility to C. acutatum was unequal. The most suitable temperature for C.acutatum development was 25 °C. Monitoring of meteorological conditions, evaluation of inoculum source and appropriate cultivar selection could reduce or avoid yield losses caused by the C. acutatum.

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