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During the past few years, frequent appearance of bacterial speck of tomatoes was recorded in several tomato-growing regions in Serbia. A three-year survey of tomato fields in Serbia (2002-2004) resulted in the isolation of numerous bacterial strains, with 30 representative strains selected for further analyses. Based on the results of pathogenicity, biochemical, and physiological tests, all strains isolated from diseased tomato plants were identified as P. syringae pv. tomato. The identity of strains was confirmed by the polymerase chain reaction (PCR), since PCR products of expected size (650 bp) specific for coronatine-producing strains of P. syringae pv. tomato were amplified from all tested strains. Study of the host range of P. syringae pv. tomato strains originating from Serbia confirmed tomato as the sole host. The reaction of tomato differential cultivar Ontario 7710 showed that the Serbian strains belonged to races 0 and 1 of P. syringae pv. tomato.

The study was focused on improvement of the integrated management strategy against green mould disease agent Trichoderma aggressivum Samuels & Gams and mushroom fly Lycoriella ingenua (Dufour) as pests of the white button mushroom Agaricus bisporus (Lange) Imbach. The impact of neem cake amendment in casing soil on regulation of the abundance of mushroom sciarid fly adults, efficacy in controlling the green mould disease agent, and mushroom yield was evaluated. Casing soil was supplemented with different concentrations of neem cake: 1, 2.5, 5, 10 and 15%. Neem cake added as a supplement to casing soil at a rate of 2.5% reduced the number of mushroom fly adults by 83.93% and green mould disease incidence by 59.6% in comparison to the control. No adverse effect on mushroom formation, yield and quality of fruiting bodies was observed at that concentration. Amendment of 2.5% neem cake in the casing soil could be recommended for application in mushroom production to control L. ingenua and symptoms of green mould disease without negative impact on mushroom yield.

Sclerotinia stem and root rot, caused by Sclerotinia sclerotiorum, is considered to be an important soil-borne disease of over 400 plant species, including a wide range of species important for agriculture. In vitro and in vivo sensitivity of S. sclerotiorum to several commercial fungicides and biofungicides was studied. The highest efficacy was achieved by boscalid (98%) and fluopyram (80%), and the lowest by a B. subtilis-based product (5%). The isolate was sensitive to all tested products in vitro. Considering the tested synthetic fungicides, fluopyram exhibited the highest toxicity (EC50=0.003 mg/l), while captan exhibited the lowest (EC50=8.94mg/l). Even lower efficacy was achieved by tea tree oil and B. subtilis-based products. The environmental impact of pesticides and biopesticides used for Sclerotinia control was assessed. Modeling of predicted environmental concentrations in soil (PECsoil), coupled with literature toxicity data, served for assessment of pesticides soil risks. A high long-term risk for earthworms was revealed for captan and thiophanate-methyl. Based on both efficacy and risk assessment results, fluopyram was found to have the best properties of all tested conventional pesticides, while tea tree oil exerted better performance than the Bacillus product. Further investigation of combined use of conventional and biopesticides might reveal new perspectives regarding effective Sclerotinia control, while simultaneously reducing negative environmental impact.

A previous study had confirmed good selective features of a biofungicide based on Bacillus subtilis Ch-13 regarding green mould disease control and increase in white button mushroom (Agaricus bisporus) production. The recommended application rate of the biofungicide in three split doses (30 + 15 + 15 ml m-2) enhanced mushroom yield by 8.41% and control of green mould disease (Trichoderma aggressivum) by 53.57%. A different application procedure of the biofungicide B. subtilis Ch-13 was then further investigated, involving six split doses (6 × 10 ml m-2) of the same total dose of 60 ml which was previously tested in three split doses. The impact of the biofungicide on fruiting body yield and its effectiveness in disease control were evaluated on white button mushroom artificially infected with Trichoderma aggressivum f. europaeum in the experimental mushroom growing room (in vivo). No statistically significant differences in disease control efficacy were found between the fungicide prochloraz (71.08%) and the biofungicide applied either in six split doses (63.05%) or three (58.43%). As for the fungicide/biofungicide positive impact on mushroom production, no statistically significant differences were detected among treatments. The B. subtilis Ch-13-based biofungicide may be applied in three split doses, as well as in six split applications, depending on the watering or picking schedule during mushroom cultivation, as both schemes showed satisfactory efficacy in disease control and positive effects on mushroom yield.

A survey of in vitro and in vivo sensitivity of Verticillium dahliae and Fusarium oxysporum to several commercial fungicides and biofungicides was undertaken. In in vitro assays, the tested isolate of V. dahliae proved to be very sensitive to difenoconazole (EC50 = 0.02 mg/l). However, under greenhouse conditions, the highest efficacy in V. dahliae control on inoculated pepper plants was recorded for a product based on thiophanate-methyl (83.10% compared to control). Among the tested fungicides, the lowest efficacy was recorded for a product based on azoxystrobin (23.10 %) with no significant difference compared to control (p > 0.05). In in vitro assays, the tested F. oxysporum isolate was the most sensitive to prochloraz (EC50 = 0.07 mg/l) and the least sensitive to fluopyram (EC50 = 1075.01 mg/l). In in vivo assay, the highest efficacy was achieved by products based on captan (95.60%), and the lowest by a product based on thiophanate-methyl (54.40%). Antagonistic activity of the bacterium B. subtilis under laboratory conditions was not satisfying. Also, the antifungal activity and spectrum of a tested product based on tee tree oil was not efficient in suppressing pepper wilting caused by V. dahliae and F. oxysporum.

The aim of this study was to test a biofungicide based on Bacillus subtilis Ch-13 and its effectiveness in the control of green mould disease of cultivated mushroom in comparison with the fungicide prochloraz. Biofungicide effectiveness in disease control and impact on yield were evaluated on Agaricus bisporus after its natural infection with Trichoderma aggressivum in a commercial mushroom growing facility. An assay for testing the microbial efficacy of the biofungicide was conducted in two different procedures involving either three or two split doses. The highest statistically significant effectiveness in green mould control was shown by the fungicide prochloraz (71.43%), followed by the biofungicide applied in tree split doses (53.57%), and finally its two doses (45.46%). The biofungicide significantly improved yield in comparison with an untreated control and the fungicide prochloraz. Three split applications of B. subtilis strain Ch-13 enhanced mushroom yield to a larger extent than its two split doses, although the same final amount was used in both procedures. Biofungicide application in three split doses increased the total mass of harvested mushrooms 8.41% compared to the untreated control, and 10.53% compared to the fungicide prochloraz. These results implied that the biofungicide should be applied in three split applications: 30 ml (second day after casing) + 15 ml (two weeks after casing) + 15 ml (after first flush, 20-25 days after casing). The biofungicide B. subtilis Ch-13 should be further investigated regarding its joint usage with chemical fungicides in different application procedures, as it showed remarkable characteristics both in terms of promoting mushroom yield and inhibiting the spread of mycopathogenic T. aggressivum.

In vitro and in vivo sensitivity of Rhizoctonia solani to several commercial fungicides and biofungicides was studied. An isolate of R. solani, derived from diseased pepper plants originating from a greenhouse in Knjaževac, Serbia, was used. The highest efficacy in R. solani control under greenhouse conditions was achieved by iprodione (95.80%, compared to control), although differences in the effectiveness of iprodione, tea tree oil, azoxystrobin and thiophanate-methyl were not statistically significant. The isolate was sensitive to all tested products in vitro. The obtained EC 50 s were: 0.43 mg/l for iprodione, 1.84 mg/l for thiophanate-methyl, 13.84 mg/l for prochloraz, 430.37 mg/l for fluopyram, 596.60 mg/l for azoxystrobin, and 496.79 mg/l for tea tree oil.

The efficacy of a formulated product of tea tree oil (TTO) and a standard copper based bactericide in combinations with acibenzolar-S-methyl (ASM) for control of bacterial spot of pepper and bacterial speck of tomato was evaluated under controlled conditions. Treatments with copper hydroxide+ASM at both application rates and TTO+ASM showed the best efficacy in control of bacterial spot disease in pepper plants (with respective efficacy values 83.5%, 83.7 % and 86.9%). Similar efficacy was achieved by treatment with copper hydroxide alone (82.2%). On the other hand, the efficacy of TTO, applied alone, was significantly lower at both rates (63.8% and 71.5%) in bacterial spot control in pepper. The same treatments (copper hydroxide +ASM at both application rates and TTO+ASM) were most efficient in suppressing the causal agent of bacterial speck disease in tomato (87%, 82.3% and 81.6%). The efficacy of treatment with the standard bactericide copper hydroxide, applied alone, was significantly lower compared to its combination with ASM (79.1%). Similarly to the bacterial spot experiment, TTO treatments alone showed lower, although satisfactory efficacy at both application rates (66.1% and 68.9%). The results of this study showed that combination of the bioactive compound - ASM with either the standard copper hydroxide bactericide or TTO significantly improved their efficacy in both bacterial spot and speck disease control, and thus implied that combining different biorational compounds, such as essential oils and bioactive products, with standard copper treatments and their inclusion into integrated management programs are of essential importance for the control of bacterial diseases of pepper and tomato.

The impact of a bioinsecticide based on azadirachtin (Ozoneem trishul 1 %) on the abundance of mushroom flies (Sciaridae: Diptera) was compared to the effect of a commercial formulation of the malathion-based chemical insecticide Etiol tečni. Experiments were conducted in three growing chambers (B6, B7 and B8) of a commercial mushroom farm "Delta Danube" d.o.o., Kovin. Casing treatments were performed in eight replications in a random block design. The azadirachtin-based bioinsecticide was applied in chamber B8 four times (0.5 ml/m2): during casing and later at seven-day intervals. The standard chemical insecticide based on malathion was applied in chambers B6 and B7 twice (2 x 0.3 ml/m2), on the third and sixth day after casing. In all three chambers, the abundance of mushroom flies was monitored by using yellow sticky traps, which were collected weekly and replaced with new ones four times at seven days intervals. The yellow sticky traps were examined in the laboratory under a binocular microscope to determine the presence and density of mushroom flies. Only one species of mushroom fly, Lycoriella ingenua (Dufour), was found on the yellow sticky traps throughout the experimental period. The average number of sciarid flies per mushroom block 15 and 22 days after treatment (DAT) was significantly lower in the test chamber B8 than in chambers B7 and B6, while there was no significant difference 30 and 36 DAT, compared to the control chamber B6. The average number of sciarid flies per mushroom row throughout the experiment was significantly lower in the test chamber B8 than in chambers B6 and B7. The results of our study suggest that the azadirachtin-based bioinsecticide can suppress populations of the mushroom fly L. ingenua and may provide a good alternative to conventional chemical insecticide.

Biofungicides based on plant oils have some advantages compared to chemical fungicides, especially considering their harmful effect on the environment. Twenty-two essential oils from Germany and Albania were assayed for inhibitory and fungicidal activity against Verticillium dahliae Klebahn, the causal agent of Verticillium wilt of pepper, using the macrodilution fumigant method. The concentrations of oils obtained in the vapour phase were: 0.02, 0.04, 0.08, 0.16 and 0.32 μl ml-1 with determined minimum inhibitory and fungicidal concentrations. The strongest activity was shown by two samples of mint oil (Mentha piperita L.) at 0.02 μl ml-1 of air, both from Germany and Albania, followed by plant essential oils of eucalyptus (Eucalyptus globulus Labilardie), black pine (Pinus nigra L.) and cade (Juniperus oxycedrus L.), and all of them were lethal to the pathogen. Nine oils: two samples of mint, cade, eucalyptus, black pine, lavender (Lavandula angustifolia Mill.), sage (Salvia officinalis L.) and rosemary (Rosmarinus officinalis L.) inhibited the growth of Verticillium dahliae, while five oils (two samples of mint, eucalyptus, black pine and cade) showed fungicidal effects on the pathogen. These results showed that mint, eucalyptus, black pine and cade essential oils have a potential for further in vivo experiments against Verticillium dahliae.

Twenty-two essential oil samples from Germany and Albania were assayed to test their inhibitory and fungicidal activity against Cryphonectria parasitica (Murr.) Barr., the major causal agent of chestnut blight on chestnut trees, using the fumigant macrodilution method. Test concentrations of the oils in air phase were: 0.02, 0.04, 0.08, 0.16 and 0.32 μl ml-1, and minimum inhibitory and fungicidal concentrations were determined. The strongest activity was shown by two samples of mint oil from Germany and Albania, and black pine at the concentration of 0.02 μl ml-1 of air for both test isolates (M1 and 4S). The tested plant essential oils also included: eucalyptus, sage, silver fir and cade. Only three samples of EOs (mint (2) and black pine) were lethal to both isolates. Sage and silver fir oils were more toxic to the M1 isolate, while cade and eucalyptus oils were more toxic to the 4S isolate. Fifteen oils: mint (2), black pine, cade, eucalyptus, silver fir, sage, pine (4), oregano, lavender, and rosemary (2), inhibited the growth of Cryphonectria parasitica, and seven oils (two samples of mint, eucaliptus, black pine, sage, silver fir and cade) showed fungicidal effects on the pathogen.

The impact of a biofungicide based on Bacillus subtilis Ch-13 on mushroom yield and efficacy in suppression of Trichoderma aggressivum f. europaeum T77 from Serbia was estimated in comparision with a similar microbial fungicide, Bacillus velezensis QST713, and the chemical fungicide prochloraz manganese. The biofungicide B. velezensis QST713 is registered for treatments of mushrooms and other crops in many countries but it is not currently available on the Serbian market. The tested B. subtilis Ch-13 fungicide enhanced mushroom yield 12%, compared with an uninoculated control, and notably more than B. velezensis QST713 applied at its higher test concentrations. Regarding the efficacy of the biofungicides in control of the compost pathogen T. aggressivum f. europaeum, B. subtilis Ch-13 applied in concentration of 3 × 108 CFU per m2 showed higher efficacy than the higher concentrations (5 × 109 and 1 × 1010 CFU per m2) of B. velezensis QST713. The biofungicide based on B. subtilis Ch-13 should be further investigated regarding its different modes of application to ensure better efficacy in disease control as it showed beneficial features in both promoting A. bisporus production and suppressing the growth of the aggressive compost pathogen T. aggressivum, the causal agent of devastating green mould disease.

A biofungicide based on Bacillus subtilis QST713 was tested for impact on yield and efficacy against a Trichoderma aggressivum f. europaeum T77 strain from Serbia by coating mushroom grain spawn and comparing the results with the chemical fungicide prochloraz manganese in a mushroom growing room. The tested B. subtilis QST713 strain did not inhibit mycelial growth of Agaricus bisporus in plots free of the pathogen, showing an impact on yield of 91.95%, which was not significantly different from an untreated control. As for the efficacy of the fungicides used against T. aggressivum f. europaeum T77, there were no significant differences between a prochloraz manganese casing treatment, and B. subtilis QST713 coating on mushroom grain spawn, as the efficacy was 70.37 and 53.09%, respectively. These results implied that the biofungicide based on B. subtilis could serve as a harmless alternative to synthetic fungicides in mushroom production, especially during serious compost green muold outbreaks caused by T. aggressivum. Furthermore, the biofungicide should be applied alone because an antagonistic reaction was detected between the fungicide prochloraz and B. subtilis QST713.

Disease control with few or no chemicals is a major challenge for mushroom growers in the 21st century. An alarming incidence of resistance to antibiotics in bacteria, and to fungicides among mycopathogenic fungi requires effective alternatives. Previous studies have indicated that various plant oils and their components demonstrate strong antimicrobial effects against pathogens on cultivated mushrooms. The strongest and broadest activity to pathogens obtained from mushroom facilities in Serbia was shown by the oils of oregano, thyme and basil. Five oils inhibited the growth of pathogenic bacteria Pseudomonas tolaasii: wintergreen, oregano, lemongrass, rosemary and eucalyptus. The essential oils of oregano, geranium and thyme were considerably toxic to the pathogenic fungi Mycogoneperniciosa, Lecanicillium fungicola and Cladobotryum spp. The strongest activity against Trichoderma aggressivum f. europaeum was shown by the oils of basil and mint. Oils of juniper and pine showed neither inhibitory nor lethal effects on mushroom pathogens. Although the fungitoxic activity of oils is not strong, they could be used as a supplement to commercial products for disease control, which will minimize the quantity of fungicides used.

Monitoring of button mushroom bacterial diseases was conducted to estimate the presence and identity of mycopathogenic bacteria and to determine the predominant bacterial pathogen in Serbia. Samples were collected from mushroom farms during 2006­2010 and also from fresh markets during 2014-2015. The collected samples showed either symptoms of brown blotch or different degrees of brown discoloration on caps and stalks of Agaricus bisporus resembling bacterial infection. The presence of bacterial droplets on gills was not recorded. The isolated bacteria were Gram-negative and fluorescent on King's medium B. In pathogenicity tests, most bacterial isolates induced superficial or sunken brown lesions with differences in the level of discoloration on A. bisporus tissue blocks after artificial inoculation. Based on LOPAT characteristics, the isolates were divided into two groups, showing characteristics of either the LOPAT group Va or group III. Based on these features and other differential biochemical characteristics, the presumptive Pseudomonas tolaasii isolates were confirmed by specific PCR. The other group of isolates was subjected to sequencing of the 16S rDNA. Based on these sequences most isolates were identified as Pseudomonas agarici, while two strains belonged to Pseudomonas fluorescens. The survey resulted in detection and identification of P. tolaasii in 11 locations and P. agarici in 7 locations in Serbian mushroom farms. Most samples from fresh markets were infected with P. tolaasii, suggesting that this pathogen has been the predominant cause of bacterial diseases in Serbian mushroom-growing facilities over the past 10 years.

Seven fungicide mixtures (epoxiconazol + metconazole, boscalid + epoxiconazole, pyraclostrobin + epoxiconazole, prothioconazole + tebuconazole, picoxistrobin + cyproconazole, azoxystrobin + cyproconazole and spiroxamine + tebuconazole + triadimenol) were evaluated for control of net blotch of barley caused by Drechslera teres, as well as yield losses, over the 2010 and 2011 growing seasons. Two applications of the fungicide combination pyraclostrobin + epoxiconazole at the rate of 1.0 l ha-1 were the most effective treatment in controlling the disease and improving yield in both experimental years. Treatments with the fungicide mixtures epoxiconazol + metconazole and spiroxamine + tebuconazole + triadimenol showed the least effectiveness in disease control, as well as yield increase.

In Europe, two fastidious phloem-limited pathogens, 'Candidatus Phytoplasma solani' (16SrXII-A) and 'Candidatus Arsenophonus phytopathogenicus', are associated with rubbery taproot disease (RTD) and syndrome basses richesses (SBR) of sugar beet, respectively. Both diseases can significantly reduce yield, especially when accompanied by root rot fungi. This study investigates the presence, geographic distribution and genetic traits of fastidious pathogens and the accompanying fungus, Macrophomina phaseolina, found on sugar beet across four geographically separated plains spanning seven countries in Central Europe. The survey revealed variable incidences of symptoms linked to these fastidious pathogens in the Pannonian and Wallachian Plains, sporadic occurrence in the North European Plain, and no symptomatic sugar beet in the Bohemian Plain. Molecular analyses unveiled the occurrence of both 'Ca. P. solani' and 'Ca. A. phytopathogenicus' throughout Central Europe, with a predominance of the phytoplasma. These fastidious pathogens were detected in all six countries surveyed within the Pannonian and Wallachian Plains, with only a limited presence of various phytoplasmas was found in the North European Plain, while no fastidious pathogens were detected in Bohemia, aligning with observed symptoms. While 16S rDNA sequences of 'Ca. P. solani' remained highly conserved, multi-locus characterization of two more variable loci (tuf and stamp) unveiled distinct variability patterns across the plains. Notably, the surprising lack of variability of tuf and stamp loci within Central Europe, particularly the Pannonian Plain, contrasted their high variability in Eastern and Western Europe, corresponding to epidemic and sporadic occurrence, respectively. The current study provides valuable insights into the genetic dynamics of 'Ca. P. solani' in Central Europe, and novel findings of the presence of 'Ca. A. phytopathogenicus' in five countries (Slovakia, Czech Republic, Austria, Serbia, and Romania) and M. phaseolina in sugar beet in Slovakia. These findings emphasize the need for further investigation of vector-pathogen(s)-plant host interactions and ecological drivers of disease outbreaks., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Duduk et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Crop losses caused by the plant pathogenic bacterium ' Candidatus Phytoplasma solani' (CaPsol) underscore the need to better understand its perplexing epidemiological pathways. Hyalesthes obsoletus (Hemiptera, Cixiidae) is a prominent CaPsol vector with three plant associations in Serbia ( ex Urtica dioica /HobsUd; ex Convolvulus arvensis /HobsCa; ex Crepis foetida /HobsCf). Another cixiid planthopper, Reptalus quinquecostatus (Dufour), has been recently confirmed as a noteworthy CaPsol vector. A multi-test study assessed the relevance of H. obsoletus associations and R. quinquecostatus populations from Crataegus monogyna and Prunus spinosa in CaPsol occurrence in sugar beet, maize, and tobacco. Molecular typing of the CaPsol strains transmitted to test plants in experimental trials provided the first evidence of HobsUd transmitting CaPsol tuf-a type to sugar beet, HobsCa infecting maize and tobacco with tuf-b type, and HobsCf transmitting CaPsol tuf-b to maize. Affiliation of R. quinquecostatus with the specific CaPsol genotype, dSTOLg, was reaffirmed in this study. The possible involvement of R. quinquecostatus in maize redness disease and tobacco stolbur was suggested, given that this cixiid was identified as a vector of CaPsol to these crops. The obtained results indicate that the tested vectors pose a threat to cultivated plants in Serbia, underscoring the need to recognize their relevance in CaPsol disease occurrences.

Two phloem-limited pathogens, ' Candidatus Arsenophonus phytopathogenicus' and ' Candidatus Phytoplasma solani', threaten sugar beet production in France, Switzerland, and Germany. Previous studies of these pathogens in Germany had focused on its western and southern regions, leaving a knowledge gap about eastern Germany. Despite their importance, this study is the first to investigate phytoplasmas in sugar beet in Saxony-Anhalt, Germany. A phytoplasma strain related to ' Ca . P. solani' is found predominant in Saxony-Anhalt, unlike in France, where ' Ca . P. solani' has a minor role compared with ' Ca . A. phytopathogenicus'. The phytoplasma strain infecting sugar beet in Saxony-Anhalt was classified into a new subgroup designated as 16SrXII-P. The multilocus sequence analysis (MLSA) of nonribosomal genes of the novel phytoplasma strain showed that it is significantly different from the reference and all previously reported ' Ca. P. solani' strains including the strain from western Germany. Analyses of sugar beet samples from previous years confirmed the presence of the 16SrXII-P strain in sugar beet as early as 2020 and also in Bavaria in southern Germany. Based on 16S rDNA analysis, ' Ca. A. phytopathogenicus' in Saxony-Anhalt is identical to strains in sugar beet in other parts of Germany and France, as well as to a strain in potato from Germany. The presence and prevalence of two phytoplasmas in sugar beet in Germany suggest that more attention should be directed toward understanding phytoplasma infection in sugar beet in this country., Competing Interests: The author(s) declare no conflict of interest.

' Candidatus Phytoplasma solani' (stolbur phytoplasma) is associated with rubbery taproot disease (RTD) of sugar beet ( Beta vulgaris L.), while Macrophomina phaseolina is considered the most important root rot pathogen of this plant in Serbia. The high prevalence of M . phaseolina root rot reported on sugar beet in Serbia, unmatched elsewhere in the world, coupled with the notorious tendency of RTD-affected sugar beet to rot, has prompted research into the relationship between the two diseases. This study investigates the correlation between the occurrence of sugar beet RTD and the presence of root rot fungal pathogens in a semi-field ' Ca . P. solani' transmission experiment with the cixiid vector Reptalus quinquecostatus (Dufour), in addition to naturally infected sugar beet in the open field. Our results showed that: (i) Reptalus quinquecostatus transmitted ' Ca . P. solani' to sugar beet which induced typical RTD root symptoms; (ii) Macrophomina phaseolina root rot was exclusively present in ' Ca . P. solani'-infected sugar beet in both the semi-field experiment and naturally infected sugar beet; and that (iii) even under environmental conditions favorable to the pathogen, M . phaseolina did not infect sugar beet, unless the plants had been previously infected with phytoplasma., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Duduk, Vico, Kosovac, Stepanović, Ćurčić, Vučković, Rekanović and Duduk.)

Rubbery taproot disease (RTD) of sugar beet was recently associated with the plant pathogenic bacterium 'Candidatus Phytoplasma solani' (CaPsol) and reported throughout the Pannonian Plain with variations in severity. Tracing CaPsol epidemiological pathways was performed in the experimental sugar beet field in Rimski Šančevi (Serbia) in 2020-2021, where an RTD outbreak was recently recorded. A molecular epidemiology approach was applied to the study of three RTD occurrence scenarios: epidemic, non-epidemic and 'absence of RTD'. As a result, Hyalesthes obsoletus ex Convolvulus arvensis was detected as a CaPsol vector to sugar beet, while two other cixiids were identified for the first time as vectors of the CaPsol-induced plant disease in crops: Reptalus quinquecostatus and R. cuspidatus. R. quinquecostatus was proposed culpable for the 2020 RTD epidemic outbreak in Rimski Šančevi when dSTOLg CaPsol strain predominated in the RTD-affected sugar beet, whereas R. cuspidatus had a negligible role in RTD occurrence and displayed ambiguous involvement in CaPsol epidemiology on a wider scale. The temporal discrepancy of the offset of CaPsol dissemination and disease occurrence is the main obstacle in predicting CaPsol-induced diseases. Predicting disease occurrence and severity can only be achieved by gaining a better understanding of CaPsol epidemiological pathways and insect vectors involved in disease outbreaks., (© 2023. The Author(s).)

Rubbery taproot disease of sugar beet (RTD), associated with ' Candidatus Phytoplasma solani', appeared in 2020 on an epidemic scale in northern Serbia and southern Slovakia, situated at opposite edges of the Pannonian Plain. In the affected locations where the disease was assessed, symptomatic sugar beets were analysed for phytoplasma infection. Additionally, multilocus sequence analyses of ' Ca . P. solani' strains on epidemiologically informative marker genes ( tuf , stamp and vmp1 ) were performed. Symptomatic sugar beets from other countries of the Pannonian Plain (Croatia, Hungary and Austria), one sample from Germany, and red beets from Serbia were included in the analyses. ' Ca . P. solani' was detected in sugar beet in all assessed countries, as well as in red beet. Molecular analyses revealed the high genetic variability of ' Ca . P. solani' with the presence of all four tuf- types (a, b1, b2 and d), 14 stamp genotypes (seven new) and five vmp1 profiles (one new). The most common multilocus genotype in Serbia, Slovakia, Croatia, and Hungary was dSTOLg (tuf-d/STOL/V2-TA). It was dominant on sites with epidemic RTD outbreaks in the Pannonian Plain and in several sugar beet fields with non-epidemic RTD occurrence suggesting the prevalence of a particular epidemiological pathway during the epidemic's phases.

Rubbery taproot disease (RTD) of sugar beet was observed in Serbia for the first time in the 1960s. The disease was already described in neighboring Bulgaria and Romania at the time but it was associated with abiotic factors. In this study on RTD of sugar beet in its main growing area of Serbia, we provide evidence of the association between ' Candidatus Phytoplasma solani' (stolbur phytoplasma) infection and the occurrence of typical RTD symptomatology. ' Ca . P. solani' was identified by PCR and the sequence analyses of 16S ribosomal RNA, tuf , secY , and stamp genes. In contrast, the causative agent of the syndrome "basses richesses" of sugar beet-namely, ' Ca. Arsenophonus phytopathogenicus'-was not detected. Sequence analysis of the stolbur strain's tuf gene confirmed a previously reported and a new, distinct tuf stolbur genotype (named ' tuf d ') that is prevalent in sugar beet. The sequence signatures of the tuf gene as well as the one of stamp both correlate with the epidemiological cycle and reservoir plant host. This study provides knowledge that, for the first time, enables the differentiation of stolbur strains associated with RTD of sugar beet from closely related strains, thereby providing necessary information for further epidemiological work seeking to identify insect vectors and reservoir plant hosts. The results of this study indicate that there are differences in hybrid susceptibility. Clarifying the etiology of RTD as a long-known and economically important disease is certainly the first step toward disease management in Serbia and neighboring countries.

Floricolous downy mildews ( Peronospora , oomycetes) are a small, monophyletic group of mostly inconspicuous plant pathogens that induce symptoms exclusively on flowers. Characterization of this group of pathogens, and information about their biology, is particularly sparse. The recurrent presence of a disease causing flower malformation which, in turn, leads to high production losses of the medicinal herb Matricaria chamomilla in Serbia has enabled continuous experiments focusing on the pathogen and its biology. Peronospora radii was identified as the causal agent of the disease, and morphologically and molecularly characterized. Diseased chamomile flowers showed severe malformations of the disc and ray florets, including phyllody and secondary inflorescence formation, followed by the onset of downy mildew. Phylogeny, based on internal transcribed spacer and cox 2, indicates clustering of the Serbian P. radii with other P. radii from chamomile although, in cox 2 analyses, they formed a separate subcluster. Evidence pointing to systemic infection was provided through histological and molecular analyses, with related experiments validating the impact of soilborne and blossom infections. This study provides new findings in the biology of P. radii on chamomile, thus enabling the reconstruction of this floricolous Peronospora species' life cycle.

Thirty-five actinobacterial isolates, obtained from button mushroom (Agaricus bisporus) substrates (i.e., compost in different phases of composting, black peat or casing layer) in Serbia in 2014-2016 were tested in vitro against the causal agents of green mold in cultivated mushroom. Out of six most promising isolates, A06 induced 42.4% in vitro growth inhibition of Trichoderma harzianum T54, and 27.6% inhibition of T. aggressivum f. europaeum T77. The novel strain A06 was identified as Streptomyces flavovirens based on macroscopic and cultural characteristics and 16S rDNA sequence and used in mushroom growing room experiments. Actinobacteria had no negative influence on mycelial growth of the cultivated mushroom in compost in situ. Isolate S. flavovirens A06 enhanced mushroom yield significantly, up to 31.5%. The A06 isolate was more efficient in enhancing yield after inoculation with the compost mold T. aggressivum (26.1%), compared to casing mold T. harzianum (8%). Considering disease incidence, actinobacteria significantly prevented green mold in compost caused by T. aggressivum (6.8%). However, fungicide prochloraz-Mn had a more significant role in reducing symptoms of casing mold, T. harzianum, in comparison with actinobacteria (24.2 and 11.8%, respectively). No significant differences between efficacies of S. flavovirens A06 and the fungicide prochloraz-Mn against T. aggressivum were revealed. These results imply that S. flavovirens A06 can be used to increase mushroom yield and contribute to disease control against the aggressive compost green mold disease caused by Trichoderma aggressivum.

ASBTRACT Toxicity of twenty-two essential oils to three bacterial pathogens in different horticultural systems: Xanthomonas campestris pv. phaseoli (causing blight of bean), Clavibacter michiganensis subsp. michiganensis (bacterial wilt and canker of tomato), and Pseudomonas tolaasii (causal agent of bacterial brown blotch on cultivated mushrooms) was tested. Control of bacterial diseases is very difficult due to antibiotic resistance and ineffectiveness of chemical products, to that essential oils offer a promising alternative. Minimal inhibitory and bactericidal concentrations are determined by applying a single drop of oil onto the inner side of each plate cover in macrodilution assays. Among all tested substances, the strongest and broadest activity was shown by the oils of wintergreen (Gaultheria procumbens), oregano (Origanum vulgare), and lemongrass (Cymbopogon flexuosus. Carvacrol (64.0-75.8%) was the dominant component of oregano oils, while geranial (40.7%) and neral (26.7%) were the major constituents of lemongrass oil. Xanthomonas campestris pv. phaseoli was the most sensitive to plant essential oils, being susceptible to 19 oils, while 11 oils were bactericidal to the pathogen. Sixteen oils inhibited the growth of Clavibacter michiganensis subsp. michiganensis and seven oils showed bactericidal effects to the pathogen. The least sensitive species was Pseudomonas tolaasii as five oils inhibited bacterial growth and two oils were bactericidal. Wintergreen, oregano, and lemongrass oils should be formulated as potential biochemical bactericides against different horticultural pathogens.

Trichoderma species, the causal agents of green mould disease, induce great losses in Agaricus bisporus farms. Fungicides are widely used to control mushroom diseases although green mould control is encumbered with difficulties. The aims of this study were, therefore, to research in vitro toxicity of several commercial fungicides to Trichoderma isolates originating from Serbian and Bosnia-Herzegovina farms, and to evaluate the effects of pH and light on their growth. The majority of isolates demonstrated optimal growth at pH 5.0, and the rest at pH 6.0. A few isolates also grew well at pH 7. The weakest mycelial growth was noted at pH 8.0-9.0. Generally, light had an inhibitory effect on the growth of tested isolates. The isolates showed the highest susceptibility to chlorothalonil and carbendazim (ED50 less than 1 mg L(-1)), and were less sensitive to iprodione (ED50 ranged 0.84-6.72 mg L(-1)), weakly resistant to thiophanate-methyl (ED50 = 3.75-24.13 mg L(-1)), and resistant to trifloxystrobin (ED50 = 10.25-178.23 mg L(-1)). Considering the toxicity of fungicides to A. bisporus, carbendazim showed the best selective toxicity (0.02), iprodione and chlorothalonil moderate (0.16), and thiophanate-methyl the lowest (1.24), while trifloxystrobin toxicity to A. bisporus was not tested because of its inefficiency against Trichoderma isolates.

In vitro antibacterial activity tests of seven biofungicides (Ekstrasol, Bisolbisan, Bisolbifit, Serenade, Sonata, Timorex, F-Stop) and two disinfectants (colloidal silver alone and in combination with hydrogen peroxide) against the Pseudomonas tolaasii strain (NS3B6) were carried out by the disc-diffusion, broth microdilution and broth macrodilution method. Biofungicides tested in this study did not exhibit any antimicrobial activity in neither one of the methods used. Disc diffusion method revealed high sensitivity of the tested P. tolaasii strain to Ecocute based on colloidal silver and hydrogen peroxide. Both microdilution and macrodilution methods identified the same MICs and MBCs of Ecocute (0.19 mg/L) for P. tolaasii strain. MICs and MBCs values of silver alone were much higher (10 mg/L) compared to silver in combination with hydrogen peroxide.

A study of the in vitro sensitivity of 12 isolates of Phytophthora infestans to metalaxyl, azoxystrobin, dimethomorph, cymoxanil, zoxamide and mancozeb, was conducted. The isolates derived from infected potato leaves collected at eight different localities in Serbia during 2005-2007. The widest range of EC(50) values for mycelial growth of the isolates was recorded for metalaxyl. They varied from 0.3 to 3.9 μg mL(-1) and were higher than those expected in a susceptible population of P. infestans. The EC(50) values of the isolates were 0.16-0.30 μg mL(-1) for dimethomorph, 0.27-0.57 μg mL(-1) for cymoxanil, 0.0026-0.0049 μg mL(-1) for zoxamide and 2.9-5.0 μg mL(-1) for mancozeb. The results indicated that according to effective concentration (EC(50)) the 12 isolates of P. infestans were sensitive to azoxystrobin (0.019-0.074 μg mL(-1)), and intermediate resistant to metalaxyl, dimethomorph and cymoxanil. According to resistance factor, all P. infestans isolates were sensitive to dimethomorph, cymoxanil, mancozeb and zoxamide, 58.3% of isolates were sensitive to azoxystrobin and 50% to metalaxyl. Gout's scale indicated that 41.7% isolates were moderately sensitive to azoxystrobin and 50% to metalaxyl.

Isolates of Cladobotryum dendroides from Serbian mushroom farms and Agaricus bisporus F56 were tested for sensitivity to selected fungicides in vitro. Chlorothalonil was the most toxic fungicide to C. dendroides isolates (EC(50) values were below 1.68 mg L(-1)). Trifloxystrobin and kresoxim-methyl were not effective in growth inhibition of C. dendroides isolates (EC(50) values exceeded 300 mg L(-1)). Metalaxyl-M+mancozeb was the most toxic fungicide to strain F56 of A. bisporus, and iprodione the least toxic. The fungicide selectivity indexes for both C. dendroides and A. bisporus indicated that iprodione, chlorothalonil, captan and metalaxyl-M+mancozeb had satisfactory selective fungitoxicity. Iprodione had the best selectivity to both the pathogen and the host, although inferior than prochloraz manganese and carbendazim, fungicides officially recommended for mushroom cultivation in European Union (EU) countries.

Twenty microfungal isolates were collected from diseased fruiting bodies of Agaricus bisporus sampled from Serbian mushroom farms during 2003-2007. Based on morphological characteristics and pathogenicity tests, the isolates were identified as Cladobotryum dendroides. The isolates of C. dendroides and A. bisporusF56 and U3 were tested for sensitivity to several selected fungicides in vitro. C. dendroides isolates were found to be more sensitive to prochloraz manganese and flusilazole + carbendazim than to the other fungicides tested (EC(50) values were 0.09 and 0.11 mg L(- 1), respectively) and weakly resistant to thiophanate-methyl (EC(50) values ranged between 6.53 and 12.09 mg L(- 1)). Selectivity indexes of the tested fungicides on both C. dendroidesand A. bisporusindicated that thiophanate-methyl, cyproconazole + carbendazim and flusilazole + carbendazim had much less selective fungitoxicity than benomyl, carbendazim and prochloraz manganese.