OCCURENCE OF FUSARIUM HEAD BLIGHT OF WHEAT IN SLOVAKIA UNDER THE NATURAL INFECTION

Occurrence of Fusarium head blight (FHB) was documented during two consecutive years in June 2011-2012 under the natural conditions in winter wheat (Triticum aestivum L.). Observations were conducted at six different localities in four climatic regions in Slovakia. Incidence and severity of FHB were evaluated at the end of flowering stage in three replications. Each replication contained 100 spikes. These data served as a basis for FHB index calculations. Obtained FHB index values indicated that the environmental conditions of the year 2011 were more favourable to the development of FHB infection. Higher FHB index values were reached at localities with precipitation higher than 100% of long-term average. Although significantly higher incidence of heads with FHB symptoms was recorded in climatic region 02 – quite warm, dry, hilly, correlation between the climatic regions was not confirmed. Except of the climatic conditions, the FHB development can be influenced by nitrogen application. The highest levels of FHB index was in coincidence with the highest and the lowest nitrogen rates applied. In all other cases, the effect of the mineral nutrition on head blight attack was unclear. Analyses of nitrogen forms applied revealed that nitrogen forms had no impact on FHB index value

Occurrence of Fusarium head blight of barley in Slovakia

Fusarium head blight and the negative influence of this dangerous disease is current worldwide problem. The aim of this work was the evaluation of incidence and severity of Fusarium head blight of barley according to different pre-crop in different locations of Slovakia. Occurrence of Fusarium head blight (FHB) was documented during two consecutive years in June 2011-2012 under the natural Fusarium infections in fields with spring barley (Hordeum vulgare). Observations were conducted at four different localities in four climatic regions in Slovakia. Incidence and severity of FHB were evaluated at the growth stages early milk to late milk in three replications. Each replication contained 100 spikes, the incidence of FHB was calculated as FHB index. During the observed period, the infestation of affected heads by FHB ranged from 0 - 12.67 %. The average infestation of heads was 5.16 % in 2011 and 5.42 % in 2012 year. Predominance intensity of FHB on infection heads were 5% or less in each locality. Higher FHB infestations were reached at Špačince (2011), Soblahov (2012) with higher precipitation when comparing long-term average. Conversely, the lowest FHB incidence was in locality with lowest precipitation in June (Veľké Úľany – 2011, Špačince – 2012). Important influence in the severity of FHB infection had also crop rotation. The highest FHB incidence was observed in localities where was maize use as a pre-crop (Špačince, 2011 – 12.67 %, Soblahov, 2012 – 11 %)

Sensitivity of Cercospora beticola to fungicides in Slovakia

Article Details: Received: 2020-03-04 | Accepted: 2020-05-01 | Available online: 2020-09-30 https://doi.org/10.15414/afz.2020.23.03.147-154The fungus Cercospora beticola Sacc. is the one of the most important pathogens on the sugar beet. The frequent application of fungicides with the same mode of action increase a risk of development of resistant strains of the pathogen. Occurrence of C. beticola resistant strains has been never researched in Slovakia. In this work, C. beticola isolates were collected from 10 localities of Slovakia and analysed for fungicide resistance in laboratory conditions. Nine fungicides with different mode of action were tested – trifloxystrobin + cyproconazole, kresoxim-methyl + epoxiconazole, azoxystrobin + cyproconazole, thiophanate-methyl + tetraconazole, thiophanate-methyl, prochloraz + propiconazole, picoxystrobin, tetraconazole, and difenoconazole. The results confirmed, that occurrence of fungicide resistance in C. beticola population was established in Slovakia. Different criteria of assessment of fungicide resistance (based on EC50 and on growth rate – inhibition percentage) showed slightly different results, but both criteria confirmed resistant C. beticola strains to thiophanate-methyl, picoxystrobin and difenoconazole. Fields with higher frequency of application of these fungicides significantly supported the development of resistant strains. Assessment of any C. beticola strains have not confirmed reduced sensitivity to active ingredients tetraconazole and prochloraz + propiconazole. The lowest level of risk of fungicide resistance was confirmed in the locality Oslany. It is very important to focus on anti-resistant strategy and reduce of using fungicides on localities, where the occurrence of resistant C. beticola strains was confirmed – Dolné Saliby (thiophanate-methyl and picoxystrobin) and Senec (picoxystrobin and difenoconazole).Keywords: sugar beet, Cercospora beticola, fungicides, in vitro, resistance, SlovakiaReferences AGGARWAL, N. K. et al. (2014). Mycobiota associated with Parthenium hysterophorus isolated from North India.  Indian Journal of Weed Science, 46(2), 155–160.ALMQUIST, C. et al. (2016). Disease risk assessment of sugar beet root rot using quantitative real-time PCR analysis of Aphanomyces cochlioides.  European Journal of Plant Pathology,  145(4), 731–742. https://doi.org/10.1007/s10658-16-0862-5BOLTON, M. et al. (2012). Characterization of CbCyp51 from field isolates of Cercospora beticola.  Phytopathology,  102(3), 298–305. https://doi.org/10.1094/PHYTO-07-11-0212BOLTON, M. D. et al. (2016). 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Changes of species spectrum associated with Fusarium head blight caused by fungicides

Fusarium head blight (FHB) is a dangerous disease of cereals in case of yield losses and mycotoxin production. The aim of this work was to estimate the influence of used fungicides on species spectrum associated with Fusarium head blight (FHB). The study was realised in Slovakia on winter wheat by natural infection of FHB. The ears were sprayed with fungicides at beginning of flowering. After development of disease symptoms, fungicide efficacy was estimated, and Fusarium species spectrum were isolated and determined in laboratory. The fungicide efficacy against FHB achieved 60.2 – 88.3 %. The highest effectivity was estimated by using of prothioconazole + tebuconazole and prothioconazole + fluoxastrobin, followed by dimoxystrobin + cyproconazole, metconazole, propiconazole + cyproconazole, and prochloraz + tebuconazole. F. graminearum was the most frequently isolated from the ears, followed by M. nivale, F. avenaceum, F. culmorum, and F. poae. Using of prothioconazole + tebuconazole, metconazole, prothioconazole + fluoxastrobin, and tebuconazole significantly decreased incidence of F. graminearum on infected ears. The incidence of M. nivale on ears was significantly increased by using of all fungicides in comparison with untreated control. The results suggest that the ear spraying by triazole fungicides could enhance the incidence of less susceptible Fusarium species in ears, especially M. nivale. The variability in fungicide efficacy of fungicides against FHB in agricultural praxis colud be affected besides multi-pathogen origin of FHB just by selective effect of fungicides on different Fusarium species

Influence of seed treatment, temperature and origin of inocula on pathogenicity of Fusarium species to wheat and barley seedlings

In presented work, the influence of host and fungicide seed treatment on pathogenicity of 4 Fusarium species and M. nivale to wheat and barley seedlings were studied in “in vitro” conditions. The effect of Fusarium and M. nivale inoculation on coleoptile growth retardation (CGR) was analysed with respect to host and the origin of the isolates. Of F. culmorum, F. graminearum and F. poae , there is no significant influence of host (barley or wheat kernels) and isolates origin on pathogenicity of the species. Of M. nivale and F. avenaceum , the pathogenicity was significantly influenced by the host and isolates origin. F. avenaceum was more pathogenic to barley than M. nivale , on wheat opposite. The pathogenicity of tested species towards barley seeds (expressed as CGR) was assessed in downward order: F. culmorum, F. graminearum, F. avenaceum, M. nivale, F. poae . Of the wheat, the order was following: F. culmorum, F. graminearum, M. nivale, F. avenaceum, F. poae . The most aggressive pathogen towards both hosts was F. culmorum and F. graminearum . The weakest pathogen of both hosts was F. poae .The fungicide efficacy (FE) of all fungicides tested was decreased towards the species with higher pathogenicity. The higher FE in wheat than in barley was observed. The significant influence of isolates origin on FE was observed by M. nivale and F. graminearum only. The average FE of difenoconazole, tebuconazole and tebuconazole + thiram against certain Fusarium and M. nivale species decreased in following order: F. poae, F. culmorum, F. avenaceum, F. graminearum, M. nivale . The FE of quazatine was decreased as follows: F. avenaceum, F. poae, F. culmorum, F. graminearum, M. nivale . The FE of iprodione + triticonazole was estimated in downward order: F. poae, F. avenaceum, F. culmorum, M. nivale, F. graminearum . The FE of carboxin + thiram decreased in following order: F. poae, F. avenaceum, M. nivale, F. culmorum, F. graminearum . The results shoved great variation of FE depending on host and tested fungal species. There is no fungicide with universal and equal FE against all Fusarium species for seed treatment. The results highlighted the importance of selection of the most effective fungicide towards the prevalent pathogen in ecosystem or in seeds, based on laboratory myco-analysis