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Herbicide residues in soil – are they an issue?
No full textThe move to conservation tillage and herbicide-tolerant crop cultivars means that crop production
is relying on herbicides for weed control more than ever before. Some herbicides (mostly
those that are applied directly to soil prior to planting crops) can remain active in soil for weeks,
months or years. This can be an advantage as it ensures good long-term weed control. However, if a
herbicide stays in soil longer than intended it may damage sensitive crop or pasture species sown in
subsequent years. However, despite the plant-back guidelines on herbicide product labels, various
site-specific factors, such as low rainfall, constrained soil microbial activity or inadequate pH, may
cause herbicides to persist in soil beyond usual expectations. This is especially the case for repeated
applications over multiple cropping seasons. Residual herbicides rely on moisture and microbial
activity to break down. So one of the consequences of a growing season being drier than average is
that herbicides applied in one season could still have significant residues in the soil, and affect crops
planted the following year. A real problem in crop production is the difficulty in identifying herbicide
residues before they cause a problem. Because the potential for each herbicide to damage crops
varies depending on soil, agroclimate and crop, comprehensive phytotoxicity thresholds (given as
soil residue concentrations) for assessing plant-back risk are not readily available. For these reasons,
degradation of each herbicide needs to be considered separately and it is also necessary to understand
the soil type and climate when trying to interpret recropping periods.
Here we focus on the potential for clomazone and imazamox residues to cause damage to tomato,
pepper and cucumber seedlings. Bioassay was conducted in loamy and sandy soils of 20, 50
and 70% field moisture capacity. Fresh and dry weight of shoots and pigment contents (chlorophyll
a and b and carotenoids) were measured as important parameters of plant sensitivity to clomazone,
while fresh weight of shoots, fresh weight and length of roots and content of water soluble proteins
were measured to examine plant sensitivity to imazamox.
Data showed that pepper was the least sensitive plant to soil-incorporated clomazone, cucumber
was slightly more sensitive, while tomato falls in a category of plants with highly sensitive to the
herbicide. The measured parameters were more distinctly inhibited in sandy than in loamy soil. Data
for the inhibition of vegetative parameters showed that all three plant species were significantly sensitive
to imazamox in soil. Pepper and tomato demonstrated fairly regular sensitivity, while cucumber
may be classified as a highly sensitive plant. The results showed that the root parameters were
more reliable indicators of plant sensitivity to imazamox in soil. Different imazamox concentrations
caused changes in contents of water soluble proteins in all three plant species. The response data
revealed no clear dependence of protein contents on rising herbicide concentrations.November 25-29, 2019, Zlatibor, Serbi
Alterations in yield of seed essential oil from Foeniculum vulgare upon infection by Cuscuta campestris
No full textSecondary metabolites and essential oils in the medicinal and aromatic plants were fundamentally
produced by genetic processing but, their biosynthesis is strongly influenced by environmental factors.
The biotic and abiotic environmental factors, affect both the quantitative amount and qualitative composition
of essential oils. The aim of investigation was undertaken to determine the effect of parasitism
by Cuscuta campestris on yield and composition of the essential oil of fennel (Foeniculum vulgare L.).
Samples of fennel were collected for investigation a fully mature seed stage. Seeds collected in
September 2017 in fields at Institute for Medicinal Plant Research “Dr. Josif Pančić”, Pančevo (Serbia).
The experiment included the following variants: N - noninfested fennel plants (control); I - infested
fennel plants. The frame (size 50 cm x 50 cm) was used for sampling. Ten frames were sampled for
each variant of the experiment. The samples collected from all quadrats were added together and
were considered to constitute an adequate sample of the community. The essential oils of fennel
were obtained by hydro-distillation in a Clevenger type apparatus. Chemical characterizations of
essential oils were done by gas chromatography (GC) using two types of detectors (flame ionization
detector (FID) and mass spectrometer (MS)).
The yields of the obtained essential oils (noninfested and infested fennel plants) were 5.6% and
5.8%, respectively. Analyses showed that the main components of essential oil isolated from noninfested
fennel plants were trans-anethole (67.0%) and fenchone (26.5%). On the other side, content of
trans-anethole in essential oil isolated from infested fennel plants (38.5%) was significantly reduced,
while the content of fenchone was increased (34.5%). As additional dominant component in essential
oil with infested fennel plants was detected methyl chavicol (19.6%). Evident differences in
the contents of the main components indicated strong influence of Cuscuta campestris on yield and
composition of the essential oil of fennel.November 25-29, 2019, Zlatibor, Serbia,
VIII КОНГРЕСС ПО ЗАЩИТЕ РАСТЕНИЙ: Интегрированная защита растений для устойчивого растительного
производства и лесного хозяйства - Сборник тезисов
25-29 ноября 2019 года, Златибор, Серби
Antimicrobial activity of twenty-eight plant essential oils against pathogenic bacteria and fungi from different horticultural systems
No full textBiopesticides based on plant oils have many ecological advantages in comparison with chemicals.
Control of bacterial diseases is very difficult due to antibiotic resistance and ineffectiveness of
chemical products, and essential oils offer a promising alternative. Six essential oils extracted from
plants originated from Serbia and twenty-two commercial essential oils from Germany and Albania
were assayed for inhibitory and lethal activity against bacterial and fungal pathogens in different
horticultural systems. Bacteria tested were: Xanthomonas campestris pv. phaseoli (bean blight),
Clavibacter michiganensis subsp. michiganensis (bacterial wilt and tomato canker), Pseudomonas
tolaasii (mushroom bacterial brown blotch). Various fungal pathogens of cultivated mushroom were
investigated: Lecanicillium fungicola var. fungicola (dry bubble), Mycogone perniciosa (wet bubble),
Cladobotryum dendroides (cobweb disease), Trichoderma harzianum, Trichoderma atroviride, Trichoderma
aggressivum f. europaeum (green mould) and phytopathogen Verticillium albo-atrum (verticillium
wilt on pepper). Minimal inhibitory and lethal concentrations were determined by applying
a single drop of oil onto the inner side of each plate cover using macrodilution fumigant method.
Among all tested substances, the strongest and broadest activity was shown by the oils of oregano
(Origanum vulgare) and wintergreen (Gaultheria procumbens) against bacteria. Mint oil (Mentha
piperita L.) and cade (Juniperus oxycedrus L.) were the most toxic to pathogenic fungi. Carvacrol
(64.0-75.8%) was the dominant component of oregano oils and menthone (37.2%) of mint oil. X.
campestris pv. phaseoli, was the most sensitive bacteria to plant essential oils, and the least sensitive
was P. tolaasii. The most susceptible fungus to plant essential oils was M. pernicosa, and the least V.
albo-atrum. These results imply that oregano, wintergreen, mint and cade oils could contribute to
disease control against different horticultural pathogens after further in vivo experiments.November 25-29, 2019, Zlatibor, Serbi
The influence of temperature on in vitro toxicity of fungicides to Dydimella applanata
No full textThe production of raspberries is significantly affected by spur blight, caused by a phytopathogenic fungus Dydimella applanata (anamorph Phoma argillacea). Current disease management strategy relies on an integrated approach involving removal and destruction of all old fruited floricanes after harvest, elimination of the first flush of young canes and several applications of fungicides, starting from the middle of April until the middle of August. Temperature that differs significantly over that period may influence toxicity of fungicides and, consequently, the effectiveness of the disease control. Many papers reported the effects of different temperatures on environmental toxicity of pesticides, or insecticide toxicity to insects. On the other side, there is almost no data available on the toxicity of fungicides to phytopathogenic fungi. Therefore, the aim of this study was to evaluate in vitro toxicity of several fungicides with different modes of action to D. applanata isolates at three different temperatures suitable for D applanata development. The effect of 11 fungicides including: copper hydroxide, mancozeb, captan, chlorothalonil, dithianon, fluopyram, boscalid, pyraclostrobin fluazinam, difenoconazole, and tebuconazole on the growth of two D. applanata isolates at 15 C, 22 C, and 26 C was tested in radial growth experiments, in vitro toxicity of the fungicides was evaluated based on their concentrations in the medium that inhibited mycelial growth by 50 % (EC-50 values) compared to the fungicide-free control medium. The results showed that toxicity of fungicides was significantly affected by temperature. At 15 C all fungicides, except copper hydroxide, were most toxic to both isolates, while, at the highest tested temperature (26 C), they were least toxic. However, because of the limited number of isolates in the present study, further research is needed to determine if an increase in temperature leads to decreased toxicity of fungicides to D. applanata
Effect of crop rotation, tillage and fertilization system on the weed seed bank: new recognition
No full textPoznavanje vertikalne distribucije semena korovskih bilajka u
poljoprivrednom zemljištu ima veliki značaj za očuvanje biodiverziteta i stabilnosti
ekosistema, kao i pri izboru i pomoći u razvoju uspešne strategije suzbijanja korova. U
radu su prikazana novija saznanja efekta primene plodoreda, obrade zemljišta i sistema
đubrenja na rezerve semena korovskih biljaka u zemljištu. Odabirom adekvatnih mera i
metoda moguće je proceniti rezerve semena korovskih biljaka u poljoprivrednom
zemljištu i spram klimatskih i zemljišnjih uslova dati prognozu zakorovljenosti u
budućem periodu
Comparison of QuEChERS with Traditional Sample Preparation Methods in the Determination of Multiclass Pesticides in Soil
No full textBackground: The increased use of pesticides leads to permanent pollution of soil, and there is a need for continuous monitoring of these agrochemicals in soil. Objective: Three methods for the simultaneous determination of 12 pesticides belonging to eight chemical groups in soil samples were tested and compared based on analytical parameters. Methods: The quick, easy, cheap, effective, rugged, and safe (QuEChERS); traditional solid-liquid extraction (SLE); and Soxhlet extraction were used for soil sample preparation, while detection and quantification of pesticides were performed using gas chromatography-mass spectrometry (GC-MS). Results: The tested methods featured good sensitivity, and with the exception for carbofuran (Soxhlet method, LOD = 29 mu g/kg), for the rest of the pesticides, the studied LODs were less than 12 mu g/kg. Except for simazine and carbofuran, LODs obtained by Soxhlet extraction were lower than values obtained by other two methods, whereas QuEChERS gave lower LODs than the traditional SLE method for all compounds except atrazine and acetochlor. The recoveries obtained applying QuEChERS, traditional SLE, and Soxhlet methods for multiple analyses of soil samples fortified at 10,75, and 200 mu g/kg of each pesticide were in the ranges 54-103,40-91, and 12-92%, respectively. Except for chlorothalonil, the highest recoveries were obtained by the QuEChERS method. Soxhlet was better than traditional SLE method for chlorothalonil, heptachlor, and aldrin; organophosphorus pesticides (fenitrothion and diazinon) and trifluralin, gave similar recoveries for both methods. All three methods were proven to be repeatable, with RSDs lower than 19%. Conclusions: Although all tested methods showed as satisfactory regarding most analytical parameters, QuEChERS method showed much better results in terms of confidence, indicating that traditional SLE and Soxhlet extraction still need improvements for determination of multiclass pesticides in soil samples
Genetic diversity and population structure of the greenhouse whitefly Trialeurodes vaporariorum from Serbia
No full textThe greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), a haplo-
diploid sap feeding insect species, is a serious polyphagous pest of greenhouse-grown vegetables
and ornamental plants and vector of many viruses worldwide. To explore the populations of this pest and
recognize potential invasion routes, the genetic diversity and population structure of T. vaporariorum
from Serbia were analysed using six microsatellite loci. PCR multiplex conditions were optimized and
tested using 88 T. vaporariorum females collected from natural populations in 10 sampling locations in
Serbia: Apatin (AP), Beograd (BG), Kovin (KO), Negotin (NE), Pirot (PI), Smederevska Palanka (SP), Subotica
(SU), Svilajnac (SV), Trbušan (TR) and Vranjska Banja (VB). The loci carried independent information,
with two to 12 alleles per locus, and total number of private alleles was 11. Observed heterozygosity
ranged from 0.105 to 0.796, deviations of the frequency of genotypes from the expected Hardy–Weinberg
equilibrium were detected in all populations, with values ranged from -0.350 (AP population,
Tvap-2-2C locus) to 0.746 (TRpopulation, Tvap-3-2 locus). The values of the Fst parameters ranged from
0.011 between populations of AP and SU, indicating a low degree of differentiation, up to 0.286 among
the SV and BG population, which had the highest degree of mutual differentiation. According to the Fst
values (analyzed by PAST software, Principal Coordinate Analysis - PCoA/ GenAlEx software and SAMOVA
2 software), three groups of populations were formed: (1) population BG, (2) populations AP, KO, SP, TR,
VB and SU, and (3) populations SV, NE and PI. The analyzed T. vaporariorum populations were grouped
in four distinct genetic clusters based on the analysis using the BAPS software. Also, BOTTLENECK 1.2.02
software identified reductions in effective size of SP population in the recent past. Populations of VB,
SU, BG and NE also had statistically significant values of the Wilcoxon test
Occurrence of Peronospora radii on chamomile in Serbia
No full textPeronospora (Oomycetes) includes highly evolved biotrophic pathogens that cause downy
mildews and induce symptoms, either systemically or predominantly localised on leaves and stems.
Nevertheless, a small monophyletic group of downy mildews (floricolous) is mostly inconspicuous
and induces symptoms exclusively on flowers. The floricolous pathogen group is still poorly characterised
and information on its biology is currently missing. The downy mildew agent Peronospora radii
belongs to the floricolous pathogen group and has recently been suspected of causing flower malformation
that leads to high production losses of the medicinal herb Matricaria chamomilla in Serbia.
Chamomile plants exhibiting flower malformation, after disease symptoms documentation and
pathogen detailed morphological description underwent histological and ultrastructural analysis
by light and electron microscopy. The presence and taxonomical assignment of the pathogen was
established by examining the ITS and cox2 loci. The recurrent presence of a disease causing flower
malformation, which in turn leads to high production losses of the medicinal herb M. chamomilla in
Serbia, enabled experiments focusing on pathogen biology.
Symptomatic chamomiles show severe malformation in flower organogenesis, including phyllody
and secondary inflorescence formation. Through histological and molecular analyses we show
that P. radii systemically infects, manipulates and takes over its plant host. Through manipulation
of flower development, the diseased plant often becomes sterile, thus converted into an organism
that serves only to sustain pathogen reproduction and propagation. These results reveal a rare example
of a host parasite interaction in which host flower organogenesis is specificaly manipulated
by a pathogen toward ensuring its own life cycle completion and dispersal. Oospore formation in
malformed flowers results in soil contamination, while early inflorescence and down formation on
malformed flowers enable secondary blossom infection and the pathogen’s dispersal by pollinating
insects. Phylogenetic analyses support floricolous Peronospora monophyly and separation of the
Serbian strains within the cox2 analysis.
Experiments validated the impact of soil-borne and blossom infections. This study provides a
deeper insight into the biology of P. radii on chamomile enabling, for the first time, reconstruction
of the life cycle of a floricolous Peronospora. The elucidation of P. radii life cycle presented herein,
besides being a significant contribution to knowledge, is essential for the development of management
strategies for controlling the disease, by adjusting cultural practices, since chemical treatments
in medicinal herb production are highly undesirable
Superior cellulolytic activity of Trichoderma guizhouense on raw wheat straw
No full textLignocellulosic plant biomass is the world's most abundant carbon source and has consequently attracted attention as a renewable resource for production of biofuels and commodity chemicals that could replace fossil resources. Due to its recalcitrant nature, it must be pretreated by chemical, physical or biological means prior to hydrolysis, introducing additional costs. In this paper, we tested the hypothesis that fungi which thrive on lignocellulosic material (straw, bark or soil) would be efficient in degrading untreated lignocellulose. Wheat straw was used as a model. We developed a fast and simple screening method for cellulase producers and tested one hundred Trichoderma strains isolated from wheat straw. The most potent strain-UB483FTG2/TUCIM 4455, was isolated from substrate used for mushroom cultivation and was identified as T. guizhouense. After optimization of growth medium, high cellulase activity was already achieved after 72 h of fermentation on raw wheat straw, while the model cellulase overproducing strain T. reesei QM 9414 took 170 h and reached only 45% of the cellulase activity secreted by T. guizhouense. Maximum production levels were 1.1 U/mL (measured with CMC as cellulase substrate) and 0.7 U/mL (beta-glucosidase assay). The T. guizhouense cellulase cocktail hydrolyzed raw wheat straw within 35 h. Our study shows that screening for fungi that successfully compete for special substrates in nature will lead to the isolation of strains with qualitatively and quantitatively superior enzymes needed for their digestion which could be used for industrial purposes
Damage to ornamental plants by grass snails (Vallonia spp.)
No full textU radu su prikazani podaci o štetnosti puževa trava (Vallonidae) u Srbiji. Ova grupa puževa je periodično štetna, ali je u primenjenom smislu neistražena u Evropi. U poslednje dve decenije nekoliko puta je registrovana štetnost vrsta Vallonia excentrica Sterki 1893 i V. pulchella (O.F.Müller 1774), na različitim vrstama ukrasnih biljka u Srbiji, ali nije pravovremeno izvršena odgovarajuća procena šteta. Nedavne štete na rezanom cveću u zaštićenom prostoru, prvi put su omogućile objektivno sagledavanje uzroka i obima šteta, kao i utvrđivanje porekla puževa trava u lejama. Ovom prilikom je prvi put uočena agregacija puževa i štete na korenu napadnutih biljaka. U radu se navode morfološke i biološke osobine valonija, kao i zoogeografski podaci. Pored toga, razmatraju se moguće tehnike suzbijanja i daju preporuke za sprovođenje odgovarajućih mera.This paper presents data on the damage caused by grass snails (Vallonidae) in Serbia. In the last two decades, the species Vallonia excentrica Sterki 1893 and V. pulchella (O.F.Müller 1774) have been registered several times on various types of ornamental plants in Serbia, but the appropriate damage assessment hasn't been done. The recent damage to cut flowers in a greenhouses, for the fi rst time, enabled an objective examination of the causes and extent of damage, as well as the origin of indoor grass snails. Implemented control measures in the greenhoses have been analyzed