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Pectinolytic bacteria cause bacterial soft rot of potato tubers. The most significant losses occur during storage. The efficacy of essential oil (EO) components carvacrol, cinnamaldehyde, d-carvone, l-menthone, R-(+)-limonene and thymol was tested against Pectobacterium carotovorum subsp. carotovorum (Pcc) and Pectobacterium atrosepticum (Pa). Disc diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests were performed in vitro, as well as potato disc and whole tuber maceration tests in vivo.Under in vitro conditions, cinnamaldehyde was the most effective against both bacteria (MIC 0.5 μL/mL, MBC 1.5 μL/mL). Both bacteria were found to be more susceptible to d-carvone (MIC 1.5–2.5 μL/mL, MBC 2.5 μL/mL) and thymol (MIC 2.5–5 μL/mL, MBC 3–5 μL/mL). R-(+)-limonene was the least effective. Results from the potato tuber disc maceration testconfirmed a significant antibacterial effect of cinnamaldehyde at a concentration of 1.5 μL/mL. No rotted area was observed on potato tuber discs after treatment with l-menthone at concentrations of 2.5 μL/mL and 10 μL/mL against Pcc. A more pronounced effect was obtained when carvacrol was used at concentrations of 5 μL/mL against Pcc and 10 μL/mL against Pa. Disease severity tests on potato tubers after soaking for 20 min at MIC concentration of the EO components followed by 7 days of incubation at room temperature and 15 °C confirmed the antibacterial activity of cinnamaldehyde (0.5 μl/ml), l-menthone (2.5 μl/ml) and carvacrol (5–10 μl/ml). Cinnamaldehyde, l-menthone, and carvacrol may be recommended for further testing to treat stored potato tubers.

The pathogenicity of five isolates of Colletotrichum acutatum species complex (CASC) was tested on artificially injured apple fruits of the cultivar 'Golden Delicious' under laboratory conditions. Then, ten apple cultivars were tested for their relative susceptibility to CASC. Differences in the pathogenicity of the CASC isolates were confirmed in the test. The highest degree of pathogenicity was showed by the isolates from the strawberry and DCSBPM J1 from the apple. No cultivars were resistant to the pathogen. The disease incidence ranged from 57.5% to 100%. The individual cultivars showed different susceptibility to the tested isolates. The cultivars 'Braeburn', 'Jonagold' and 'Rubinola' showed the least susceptibility to the pathogen, while the cultivars 'Jonagored' and 'Otava' were recorded as the most susceptible to CASC. All the tested isolates were confirmed, by the conventional PCR method, to belong to CASC. The sequences of isolates DCSBPM J1 and DCSBPM 1209 were deposited in the GenBank.

Potato silver scurf, caused by the fungus Helminthosporium solani, is an important storage disease of potato (Solanum tuberosum L.), reducing the market value of tubers. Using in vitro and in vivo assays, the presented experiments aimed to determine the effect of selected essential oils (EOs: α-pinene, carvacrol, cinnamaldehyde, D-carvone, eucalyptol, L-linalool, L-menthol, L-menthone, (R)-(+)-limonene, and thymol) on H. solani growth. All EOs inhibited pathogen growth, but their antifungal activities differed significantly. Thymol, carvacrol, and cinnamaldehyde had the strongest inhibitory effects on mycelial growth under in vitro conditions. (R)-(+)-limonene displayed the weakest inhibition. The effectiveness of those EOs with the greatest antifungal activity was confirmed by in vivo experiments. EOs were applied through dressing and fumigation, with EOs bound to a biopolymer for dressing. Dressing and fumigation brought a highly statistically significant reduction in H. solani infection intensity and sporulation intensity on tubers. Although EOs had an insignificant effect on potato cooking quality, the taste of EO-dressed tubers was degraded by an off-odor and off-taste. EOs could provide an ecological alternative for reducing H. solani tuber infection during storage.

During 2011–2013, the frequency of occurrence and species spectrum of Fusarium fungi occurring on grains of five malting varieties of spring barley (Aksamit, Bojos, Malz, Radegast, and Kangoo) were monitored at two locations (Kroměříž and Žabčice, Czech Republic). The effect of three fungicide treatment variants on Fusarium species suppression was also evaluated. During the monitored period, five species were detected: F. poae, F. culmorum, F. graminearum, F. avenaceum, and F. tricinctum. The most frequently isolated species was F. poae. Radegast had the highest frequency of naturally occurring Fusarium fungi, while Kangoo was the least infected variety at both locations. The greatest fungicide effectiveness against Fusarium spp. occurrence on ears was recorded after the variant with application of Hutton at BBCH 39 and Prosaro 250 EC at BBCH 65. During the monitored years, Žabčice had a higher rate of infection by Fusarium fungi. The rates of barley infection by Fusarium pathogens differed among individual years, with the highest rate occurring in 2011 (16–17 %) and the lowest rate in 2012 (1–2 %).

Laboratory tests of six isolates of the pathogen Colletotrichum acutatum from different host plants demonstrated the varying sensitivity of pathogen with regard to mycelium growth and conidial germination after treatment with seven fungicides containing various active ingredients. None of the evaluated isolates was tolerant to the selected active ingredients in the fungicides. In tests of mycelium growth sensitivity, isolates from lupin and strawberry were most frequently identified as the most sensitive of all evaluated fungicides. The safflower isolate, on the other hand, most frequently exhibited the lowest reaction to fungicides. Differences in conidial germination of individual isolates were not detected in fungicides with the active ingredients dithianon, folpet and mancozeb, for which inhibition reached 100% in almost all isolates. The most significant differences in sensitivity among individual isolates were recorded in fungicides with the active ingredients azoxystrobin and metiram. In the case of the fungicide with active ingredient azoxystrobin, the highest inhibitory effect was achieved in the safflower isolate and the lowest in the white lupin isolate. After treatment with the fungicide with active ingredient metiram, the lowest germination rate was recorded in isolates from safflower and strawberry and the highest in isolates from hypericum and lupin.

The influence of plant growth stage, inoculum density, and variety on the disease severity and incidence were studied. Our results indicated that growth stage of the plant had no influence on infection rate, as the pathogen attacked 100% of tested plants. When applying three different inoculum concentrations to three weeks old safflower plants, no statistical differences were recorded, disease incidence ranged 32.0-47.0%. In this test, the 3rd and 4th evaluated leaves (the youngest) were infected more intensively than were the 1st and 2nd leaves. Among 11 safflower varieties tested for resistance to this pathogen, cultivar CW 1221 manifested the highest resistance with 8.3% infection, whereas two cultivars, Sabina and AC Sunset, were found to be the most susceptible with 90.0 and 83.3% infection.

Resistance of determinant tomato varieties to pathogens causing bacterial wilt disease – Clavibacter michiganensis subsp. michiganensis (Cmm) and Ralstonia solanacearum (Rs) – was tested under greenhouse conditions. In tests to Cmm resistance, two inoculation methods were compared (inoculation “to the cut off top” of a plant and inoculation by three punctures into a stalk). The inoculation method “into a stalk” appeared to be most suitable. In both cases of inoculation, the highest level of resistance was found in Minigold variety. The rather high level of resistance was also found in varieties Aneta and Orange. In tests to Rs resistance, the most resistant varieties were Minigold, Aneta and Orange, which are recommended for direct consumption.

Colletotrichum acutatum belongs to polyphagous fungal pathogens and is widespread in many countries on all continents. C. acutatum causes the most serious economic damage in strawberry (Fragaria x ananassa Duch.). Considering the wide variability of the pathogen may be assumed spread to other areas which constitutes danger not only for strawberry, but also other economically important fruit crops, vegetables and fruits.The main objective of our study was to verify the cross infection of eleven C. acutatum isolates from different host plants (strawberry, safflower, lupine, pepper and Hypericum perforatum) to selected host plants (strawberry, pepper and safflower). Two varieties from each of the experimental plant species were selected and virulence of isolates C. acutatum was evaluated.Based on results of statistical evaluation, virulence of C. acutatum isolates was different on strawberry, pepper and safflower. The strawberry variety Pegasus was more susceptible to C. acutatum than the variety Elkas. Isolate 710 from H. perforatum showed the highest virulence for both varieties in terms of index of infection intensity. The pepper variety Pirouet was more susceptible than the variety Cynthia. The highest degree of virulence was found for isolate 29267 from pepper in the variety Cynthia, the highest virulence was proved for isolate 231 from strawberry in the variety Pirouet. No statistical difference was confirmed between susceptibility of the safflower varieties. Isolate 1209 from safflower showed the most important effect on tested plants of safflower. Isolates 710 from H. perforatum, isolate 1209 from safflower, isolate 29267 from pepper and isolate 231 from strawberry showed different virulence for tested host plants.