This study evaluates the antibacterial and antifungal effects of ethanol extracts from Gnaphalium uliginosum L. derived from freshly harvested plant biomass, including stems, leaves, flowers, and roots. The extract was analyzed using gas chromatography-mass spectrometry (GC-MS) to determine its antimicrobial activity against phytopathogenic bacteria and fungi. Two methods were used in the experiments: agar well diffusion and double serial dilution. Extraction was carried out using the maceration method with different temperature regimes (25 °C, 45 °C, and 75 °C) and the ultrasonic method at various powers (63–352 W) for different durations (5 and 10 min). It was found that the 70% ethanol extract obtained through the ultrasonic experiment at 189 W power for 10 min and at 252 W power for 5 min had the highest antimicrobial activity compared to the maceration method. The most sensitive components of the extracts were the Gram-positive phytopathogenic bacteria Clavibacter michiganensis and the Gram-negative phytopathogenic bacteria Erwinia carotovora spp., with MIC values of 156 μg/mL. Among the fungi, the most sensitive were Rhizoctonia solani and Alternaria solani (MIC values in the range of 78–156 µg/mL). The evaluation of the antimicrobial activity of extracts using the diffusion method established the presence of a growth suppression zone in the case of C. michiganensis (15–17 mm for flowers, leaves, and total biomass), which corresponds to the average level of antimicrobial activity. These findings suggest that G. uliginosum has potential as a source of biologically active compounds for agricultural use, particularly for developing novel biopesticides.

Background: Plants are an important source of biologically active compounds that can be used as crop protection agents. When using them, it is important to take into account the period when these biologically active substances accumulate in the plant to the maximum level. This article presents the results of a study on the antibacterial and antifungal activity of ethanol extracts obtained from Centaurea montana, Centaurea macrocephala and Psephellus dealbatus at different stages of their development. Methods: Plants of Centaurea montana, Psephellus dealbatus and Centaurea macrocephala were grown in the experimental fields of the Tatar Research Institute of Agriculture in the Republic of Tatarstan, Russian Federation. Extracts were prepared from the freshly harvested biomass using single maceration with stirring. In experiments, the minimum inhibitory concentration (MIC) of bacterial and fungal extracts from C. montana and P. dealbatus and C. macrocephala were determined using a double sequential dilution method in a liquid medium. To determine the minimum bactericidal and fungicidal concentrations (MBC and MFC), 10 μl of an inoculum (or a piece of fungal mycelium) was added to agarized nutrient media in Petri dishes using a bacteriological loop, taken from test tubes without visible growth. Result: Extracts from the buds, flowers, leaves and stems of these plants exhibited the greatest antimicrobial activity during the budding and early flowering stages. Bacterial growth was inhibited at an extract concentration of 625 µg/ml and fungal growth at a concentration of 312 µg/ml. The data obtained demonstrates the potential of using these ethanol extracts as herbal preparations for combating plant pathogens during the budding and early flowering periods.

Phytopathogenic nematodes have a negative impact on crop productivity. Currently, the main method of controlling these pests is the use of synthetic nematocides. Despite their high efficacy and ease of use, synthetic nematocides can pose a risk to both agricultural producers and consumers of crop products. An alternative to the use of chemical plant protection products can be the use of substances of natural origin, such as plant extracts. When using plant extracts to control agricultural pests, it should be borne in mind that the biological activity of extracts depends not only on the plant species, but also on the method of obtaining the extract. This work presents data on the physicochemical properties and biological activity of the extracts of Tagetes patula Lemon Drop variety obtained using four extractants of different polarity: ethanol, chloroform, n-hexane and methyl tert-butyl ether. The pH, total carotenoids, phenols, flavonoids and thiophenes content were determined for each extract. The biological activity of the extracts was studied in experiments with the free-living soil nematode Caenorhabditis elegans. All extracts had dose-dependent toxic effects on C. elegans organisms. The toxicity of the extracts depending on the solvent decreased in the series: chloroform > ethanol > n-hexane > methyl tert-butyl ether. The revealed differences in nematocidal activity of the extracts correlated with the content of phenols and carotenoids in them.