ABSTRACT The production of green leafy vegetables is an important segment in agriculture, because they are the source of functional compounds that are beneficial for human health. The main objective of this study was to determine the effects of plasma activated water (PAW) treatment on the morphological, qualitative and chemical properties of spinach under greenhouse and field growing conditions. The application of PAW has a significant influence on plant height, plant diameter, green mass and dry matter, as well as on the content of bioactive substances (phenols, flavonoids, proline) under both cultivation conditions. The results of this study show that the application of a higher dose of PAW (PAW 2) resulted in 46% higher green mass of spinach under field conditions and 57% higher green mass under greenhouse conditions compared with the control varieties. The application of PAW 2 increased the dry matter of the plants by 53% under field conditions and by 75% under greenhouse conditions compared with the control varieties. Similar results were obtained with respect to proline content under field conditions, which increased by 30% with the application of PAW 2 compared with the control varieties and by 50% in the greenhouse with the application of PAW 1. The results indicate that PAW treatment can be a useful method to improve the growth and nutritional quality in spinach cultivation under different climatic and growing conditions.

The study investigated the insecticidal efficacy of six Croatian inert dusts (D-01, JU-1, MA -4, MR -10, OP -4 and PD -1) and diatomaceous earth Celatom Mn-51 (R) against red flour beetle Tribolium castaneum Herbst on wheat. The influence of mentioned dusts on the offspring development has also been investigated. The experiment was carried out in laboratory conditions on insects aged 7-21 days. Doses of 600 and 700 mg kg (-1) were tested for JU-1, MR -10, OP -4 and PD -1 and 300 and 400 mg kg -1 for D-01, MA -4 and Celatom Mn-51 (R) alongside previously mentioned doses (600 and 700 mg kg (-1) ). The mortality rate of red flour beetle was determined on the 7th and 14th day of exposure and progeny was determined by number of developed adults. Regarding the insecticidal efficacy on T. castaneum the tested inert dusts can be divided into three groups: very effective dusts (D-01 (LD 90 = 600 mg kg (-1) ), MA -4 (LD 90 = 500 mg kg (-1) )), medium -effective dusts (JU-1 and PD -1) and low -efficient dusts (OP -4 and MR -10). Based on the obtained results it can be concluded that there are some resources of inert dusts with high insecticidal potential in the Republic of Croatia.

The study investigated the insecticidal efficacy of six Croatian inert dusts (D-01, JU-1, MA-4, MR-10, OP-4 and PD-1) and diatomaceous earth Celatom Mn-51® against red flour beetle Tribolium castaneum Herbst on wheat. The influence of mentioned dusts on the offspring development has also been investigated. The experiment was carried out in laboratory conditions on insects aged 7-21 days. Doses of 600 and 700 mg were tested for JU-1, MR-10, OP-4 and PD-1 and 300 and 400 mg for D-01, MA-4 and Celatom Mn-51® alongside previously mentioned doses (600 and 700 mg ). The mortality rate of red flour beetle was determined on the 7th and 14th day of exposure and progeny was determined by number of developed adults. Regarding the insecticidal efficacy on T. castaneum the tested inert dusts can be divided into three groups: very effective dusts (D-01 ( = 600 mg ), MA-4 ( = 500 mg ), medium-effective dusts (JU-1 and PD-1) and low-efficient dusts (OP-4 and MR-10). Based on the obtained results it can be concluded that there are some resources of inert dusts with high insecticidal potential in the Republic of Croatia.

Three-of-heaven (Ailanthus altissima (Mill.) Swingle) is considered as one of the most invasive plant species worldwide in rural and urban environment. Although tree-of-heaven is commonly observed throughout the city of Osijek (Croatia), its prevalence and frequency has not been documented. This study has been conducted from May to September 2022 in the streets of Osijek to determine the distribution, abundance and competitive advantage of this species. A survey was performed by sampling randomly selected 20 quadrats in each city district, having together 140 phytocoenological records, and presence-absence of tree-of heaven was recorded in each plot. Where present at urban habitats, the number of threes were recorded and categorized approximately by the diameter at breast height (dbh). Habitats were distinguished as follows: alleys, abandoned private areas, public areas, ruderal sites, cracked walls and road edges. Risk assessment analysis were prepared by combining quantitative (number of trees per plots) and qualitative (four categories: biological characteristics and dispersal abilities, ecological amplitude and distribution, ecological impact, and difficulty to control) data. There was e recorded a total of 189 tree-of-heaven, occurring both as solitary plants or in developed stands. The habitat types with the highest rate of tree-of-heaven are abandoned private areas (34%) followed by public areas (31%). Out of the total, 55% of the recorded tree-of heaven are young individuals belonging to the very small and small diameter classes, and are mainly present on abandoned private and public areas. Ecological impact and biological characteristics are primary course of its landscape spread.

Field studies were conducted in the northeastern part of the Republic of Croatia to determine the influence of the critical period of weed interference on sunflower (Helianthus annuus) yield, yield components, and oil content. For this purpose, different durations of competition were established, allowing weeds to infest the crop for increasing periods of time after planting or maintaining plots weed-free for increasing periods of time after planting. The beginning and the end of the critical period of weed control (CPWC), based on a 5% and 10% loss of sunflower yield, were determined by fitting the four-parameter log-logistic equations to the relative seed yield. The total weed biomass increased progressively in relation to the increase in the competition. The beginning of the CPWC period, based on a 5% acceptable yield loss, ranged from 141 to 234 growing degree days (GDD), which corresponded to the two-to-four true leaf development stage (the V2–V4 growth stages) across both sites and years. The crop had to be kept weed-free until a period when sunflower inflorescence began to open and flower (the R4–R5 growth stage) or from 1365 to 1932 GDD. The sunflower yield and yield components varied between the years and among locations. An increasing duration of weed interference negatively affected crop height, head diameter, and 1000-kernel weight, but not seed oil content.

Three-of-heaven (Ailanthus altissima (Mill.) Swingle) is considered as one of the most invasive plant species worldwide in rural and urban environment. Although tree-of-heaven is commonly observed throughout the city of Osijek (Croatia), its prevalence and frequency has not been documented. This study has been conducted from May to September 2022 in the streets of Osijek to determine the distribution, abundance and competitive advantage of this species. A survey was performed by sampling randomly selected 20 quadrats in each city district, having together 140 phytocoenological records, and presence-absence of tree-of heaven was recorded in each plot. Where present at urban habitats, the number of threes were recorded and categorized approximately by the diameter at breast height (dbh). Habitats were distinguished as follows: alleys, abandoned private areas, public areas, ruderal sites, cracked walls and road edges. Risk assessment analysis were prepared by combining quantitative (number of trees per plots) and qualitative (four categories: biological characteristics and dispersal abilities, ecological amplitude and distribution, ecological impact, and difficulty to control) data. There was e recorded a total of 189 tree-of-heaven, occurring both as solitary plants or in developed stands. The habitat types with the highest rate of tree-of-heaven are abandoned private areas (34%) followed by public areas (31%). Out of the total, 55% of the recorded tree-of heaven are young individuals belonging to the very small and small diameter classes, and are mainly present on abandoned private and public areas. Ecological impact and biological characteristics are primary course of its landscape spread.

Weed infestation is a major cause of the poor yield of soybeans (Glycine max (L.) Merr.); therefore, proper weed management represents one of the most important and expensive steps in soybean production. Field experiments were established in northeastern parts of Croatia, in the Vukovar-Syrmia county from 2014 to 2016, arranged in a split-plot design with four replications. Two different studies were conducted: the first study was to determine the weed interference, weed biomass accumulation, yield, and yield components of soybeans growing in three different rows spacing (25, 50, and 70 cm), and the second study aimed to simulate a risk analysis by building models of probabilities for generating profit as a result of weed control. The weed community in soybean during the study period comprised 34 dicot and grass species of a varied perennation. Compositional differences in the weed community tended to be affected most by the year (humid–arid environment), followed by row spacing. There were no differences in the weed biomass accumulation with a reduction in row spacing from 70 to 50 and 25 cm. The dominant weed species Amaranthus retroflexus, Ambrosia artemisiifolia, Chenopodium album, Datura stramonium, Setaria viridis, and Sorghum halepense formed the main biomass and were spread over all row spacings. There was a significant influence of row spacing, the duration of weed interference, and year on soybean yield and yield components. Weed infestation until the second trifoliate (V2) stage had no detrimental effect on soybean yield, regardless of the row spacing. The number of pods per plant significantly decreased at the same V2 stage in 25 and 50-cm rows, but in 70-cm soybean rows, this process started later, at four unfolded trifoliate leaves (V4 stage). A 1000 kernel weight was less sensitive to weed infestation and was significantly decreased at full flowering (R2 stage) in 25 and 70 cm rows, while it already decreased at the V4 stage in 50 cm rows. The probability distribution of achieving a profit showed the best results for soybeans growing in 70 cm rows, with preemergence herbicide application and two inter-row cultivation.

Bracken (Pteridium aquilinum (L.) Kuhn) is cosmopolitan fern, found at varying altitudes on all continents except Antarctica. It is an aggressive colonizer and can appear in various plant communities, but an important characteristic is its ability to dominate in dense patches. Once establish, the deep-set rhizomes are nearly impossible to eradicate. In Croatia, bracken dominate on specific habitat type called “bujadnice” in Lika region, but can also be found in herbaceous layers in following forest communities: As. Betulo-Quercetum; As. Pteridio-Betuletum; As. Potentillo albae-Quercetum pubescentis; As. Castaneo sativae-Fagetum; As. Helleboro nigri-Piceetum. Bracken fern is significant problem for livestock-based extensive agriculture, because it causes a range of syndromes in farm animals including thiamine deficiency, acute hemorrhagic syndrome, bright blindness, enzootic hematuria and upper alimentary carcinoma. Man may consume the toxins of bracken either directly or indirectly. In terms of the economic loss and suffering caused by bracken, it is clearly that some steps must be taken to control distribution of this fern. Timing is important in any management treatment of bracken fern. The most effective time for bracken control is summer just after the new fronds have fully expanded and starch reserves in the rhizome are at their lowest level. Two or more annual treatments and combinations of cutting and herbicide are more effective than single treatments or even single annual treatments.

Non native, and especially invasive plants, often have a negative impact on biodiversity, economy, and even on human health. They have rapid reproduction potential and are capable for dispersal over significat areal. They have a negative impact on biological diversity, economy and even on human health. Therefore, the spread of invasive plant species is consider as one of the biggest problems in nature protection. Research on prevalence and risk assesment of invasive vascular flora in Pozega valley were conducted during the summer months from 2017 to 2019 using the Br. -Bl. (1964.) cover/abundance method. A thirty four invasive species were detected during the study period. Analysis according to family affiliation, life form, geographic origin and invasion stage were made. Multivariate statistical technique -CCA were use to analyse relation between elevation and cover values of invasive flora of Pozega valley. The most numerous families are Asteraceae and Poaceae. Life-form analysis showed the predominance of therophytes, but also presence of hemicryptophytes, phanaerophytes, geophites and hydrophyte. Regaridng origin, majority of invasive alien species come from American continent, particularly from North America, followed by those from Asia and Africa. Most of them (47%) are in the stage of invasion i.e. colonisation. Many of them are already naturalised, and in invasion phase. Lowlands (elevation up to 200 m) are favorable sites for most of the invasive plants, and just small amount of them, like Phytolacca americana L. and Ailanthus altissima (Mill.) Swingle are positively correlated with the hilly areas. The most affected by the invasion are ruderal and agricultural habitats.

Field study tested weed control efficacy, crop yield and economic return using various weed management strategies in sunflower growing with different population density. Treatments included four rates of PRE emergence application of S-metolachlor + fluchloridon and one POST emergence application of flumioxazin + quizalofop-pethyl. PRE-em application (1.4 + 2.4 and 1.2 + 2.0) provided at the higher crop densities (70 000) best weed control. However, PRE- em treatments with lower doses (0.8 + 1.6 and 1.0 + 1.8) and POST- em application did not maintain acceptable control of dominant weeds. Grain yield increased with the crop density, but did not statistically differ between applied herbicide treatments. Finally, the implication of this study demonstrated that sole application of tested herbicide treatments at higher crop sowing density (60 000 and 70 000) was found to be economically the best alternative strategy for reducing weed infestation and achieving a better yield.

Strane, a posebno invazivne vrste često imaju negativan učinak na biološku raznolikost, ekonomiju, pa i ljudsko zdravlje. One su sposobne proizvoditi produktivno potomstvo i posjeduju potencijal širenja na značajnim površinama. Stoga je širenje invazivnih vrsta jedno od najvećih problema u zaštiti prirode. Praćenje rasprostranjenosti i procjena rizika invazivne vaskularne flore Požeške kotline vršeno je tijekom ljetnih mjeseci od 2017. do 2019. godine putem kombinirane procjene brojnosti i pokrovnosti. Istraživanjima je utvrđeno ukupno 34 invazivne svojte vaskularne flore kojima je pridružena porodica, životni oblik, geografsko porijeklo te je procjenjena faza procesa invazije. Za analizu povezanosti između nadmorske visine i pokrovnih vrijednosti invazivne flore Požeške kotline, primjenjena je multivarijantna statistička tehnika - CCA analiza. Najbrojnije vrstama su porodice Asteraceae i Poaceae. Analiza životnih oblika izdvojila je dominaciju terofita, ali i prisutnost hemikriptofita, fanerofita, geofita i hidrofita. Po porijeklu invazivne biljke pronađene u Požeškoj kotlini dolaze prvenstveno sa američkog područja, posebice Sjeverne Amerike, a zatim slijede one iz Azije i Afrike. Većina zabilježene invazivne flore nalazi se u stadiju ekspanzije tj. kolonizacije. Dobar dio je već naturaliziran, a dio je u fazi introdukcije. Nizinska područja do 200 m nadmorske visine pogoduju najvećem broju invazivnih biljaka. Samo manji broj biljnih vrsta je pozitivno koreliran s brežuljkastim područjima gdje se ističu vrste Phytolacca americana L. i Ailanthus altissima (Mill.) Swingle. Najviše zahvaćeni invazijom su ruderalna i poljoprivredna staništa.

During floristic studies within the Papuk Nature Park protected area (Northeast Croatia), on the Lapjak ridge, at an altitude of 452 m, a locality of the taxon Seseli elatum L. ssp. osseum (Crantz) P.W.Ball has been documented. This taxon is very rare on the Papuk Mt: it grows in the boulder cracks or between rocks in the rocky grasslands. The locality has southern exposition, with an inclination of 30%–40%, and a carbonated baserock (dolomite) with very scanty shallow brown carbonated soil (rendzina). The area is 20×30 meters in size. The research was conducted on 20th August, 2015 and a list of plant taxa species was compiled and compared to earlier lists (in 1993 and 1997). The floristic elements, life forms and ecological factors have been determined according to Ellenberg. Plants from the South European floristic element dominated the grassland flora (35.7%). Hemicryptophytes were the dominating life form (48.6%), while in terms of ecological factors, light-loving plants dominated. The plant is very rare in the Republic of Croatia and that locality is the single documented site of Seseli elatum L. ssp. osseum (Crantz) P.W.Ball in the area of Požega Valley and the surrounding mountains.

A vegetation survey in northeastern Croatia explored the influence of intensive arable farming on the weed community in relation to the crop edge and adjacent field margin. A total of 141 vascular plants were recorded, and significant differences among the species appear in the field margins (134) as compared to the crop edges (109) and middle of the fields (49). Native plants predominated (83.7%), but among non-natives, the most abundant were Ambrosia artemisiifolia L., Abutilon theoprasti Med. and Veronica persica Poir., with the highest cover values inside the cropped areas, particularly during spring sowing of row crops. The most diverse (having significantly higher Evenness and Shannon?s diversity index) was the community from the field margin, followed by the weed community that developed on the crop edges. Three distribution patterns were observed: weeds typically limited to the crop area, weeds limited to the non-crop area and weeds with some ability to spread from the field margins. Major variations in species composition were identified according to sowing season and crop type. Wind dispersal annuals with light- and nitrogen-demands were associated with disturbed, tilled habitats, while perennials with higher requirements for moisture and other than a wind mode of dispersal, were associated with the field margins.

A field experiment was conducted to evaluate various weed management options on garlic (Alium sativum L.) production in Northeastern Croatia. This study focus on how different strategies of weed control affects weed community composition and economic benefit of weed management. An experiment was arranged as a complete block design with three different weed management strategies: chemical control (PRE EM and POST EM), mechanical control (three times during the season), and combination of chemical and mechanical treatments, together with weeded checks. Data on weed density, fresh above weed biomass and garlic yield per m2 were collected at the end of the growing season, and were subjected to statistical and economic analysis. The mayor weeds found in the experimental plots were: Sorghum halepense, Ambrosia artemisiifolia, Cirsium arvense and Chenopodium album. The various weed growth (density and biomass) and yield varied with application of weed management practices. Significantly lower values of weed density and fresh above weed biomass were recorded on plots with mechanical and combination of chemical and mechanical treatments compared to weeded check. Chemical application gave in this study insufficient weed control and resulted in lower yields compared to the mechanical treatments and combination of mechanical and mechanical weed control. The best cost: benefit ratio was observed on treatment with combination of chemical and mechanical weed control and can be successfully applied to boost up the bulb yield in garlic and to harvest the maximum profit for farmers.

Field margins are pollinator-friendly habitats and important refuges for many pollinators. As a valuable food resource throughout the vegetation season, not just when crop species are in flower, field margins need to be protect or restore in areas of intensive farming. This paper examines the floristic and functional structure of weed communities on field margins in the northeastern part of the Republic of Croatia. A phytocoenological survey was conducted during the summer period of 2017 and 2018. A total of 32 field margins was analyzed for species richness, abundance and their role for entomofauna. Floristically rich field margins consist of 72,6% plant species beneficial to pollinators. Foraging period can be stretching throughout the year, but stabile and high flowering period is from May to end of September. Among highest ranked honeybee plants, several invasive species with significant relative abundance are: Solidago gigantea, Asclepias syriaca and Amorpha fruticosa who pose a serious threat to plant biodiversity. Positive role of vegetation from field margins was not valuable for pollinators only, but they also serve as supply the substrates that provide a shelter and nesting sites.

Dodders are cosmopolitan parasitic rootless and leafless plants, only minimally photosynthetic, and entirely dependent on the host. Among them, field dodder (Cuscuta campestris Yunck.) is the most widely distributed dodder species that can cause a serious problem in sugar beet production in many areas around the world. Depending on the severity of infestation, dodder can reduce the sugar beet yield by 20-100%. Distribution and abundance of field dodder has become significant in northeastern Croatia sugar beet fields, showing 30% of high and 10% of severe dodder infestation. A similar pattern has been observed in the surrounding fields and rural habitats with severe dodder attack occurring particularly in alfalfa fields. Dodder has a broad host range, and has preference. During this study, a total of 28 weed species served as dodder hosts. The host weed species having a strong association with the sugar beet crop were Conyza canadensis, Solanum nigrum, Datura stramonium, Amaranthus retroflexus and Atriplex patula. However, many other weeds can support dodder development in other fields, field borders and non-crop areas. Their soil can become a reservoir of dodder seeds during the years when non-host crops are grown. They are Polygonum aviculare, Polygonum persicaria, Polygonum lapathi-folium, Convolvulus arvensis and Chenopodium album.

This paper analyses the floristic biodiversity of weed communities in the arable lands of the Istrian peninsula during a twelve year period (2005–2017). A total of 50 fields were surveyed for each sampling time using the seven-degree Braun-Blanquet cover abundance scale in the following agricultural categories: a) permanent crops (vineyards/olive groves), b) alfalfa fields, c) cereals, d) row crops and e) ruderal areas. The taxonomic identification was performed during the full development of vegetation, for cereals in June and July, and for the rest – in August and September. A total of 175 weed species were determined during both study periods with Asteraceae and Poaceae families as the most abundant. Altogether, therophytes were dominant in both surveys, followed by hemycryptophytes and geophytes. Variations in species composition were visible in both study periods (2005 and 2017) as well as in the selected habitat types. Exclusive species were found in addition to those that were common for both surveys. Changes in species composition between 2005 and 2017 referred to the difference in row spacing in earlier period, and ruderal vs. agricultural habitats in the recent survey. The differences in phenological traits between the past and present surveys were greatest for germination season in permanent crops and row crops, flowering start for permanent crops, flowering period for ruderal area and weed height for permanent crops. Significant differences between the past and present survey for other plant traits did not occur.

Na blago valovitim istočnim obroncima Psunja razvijeni su suhi brdski travnjaci, koji predstavljaju jedan od najugroženijih oblika vegetacije,a bili su predmet ovog istraživanja. Teren je blago nagnut prema jugoistoku, južne je ekspozicije, nadmorska visina oko 400 m. Cilj istraživanja bio je utvrditi brojnost i raznolikost samonikle vaskularneflore travnjaka na području Rudine. Floristička istraživanja vršena su 2003., 2008., 2016. i 2017. godine. Na površini od oko 2500 m2 popisane su i determinirane biljne svojte, određena njihova pripadnost porodicama, flornim elementima i životnim oblicima. Zabilježeno je 186 biljnih svojti vaskularne flore unutar 46 porodica i 134 roda. Izvršena je taksonomska, ekološka i fitogeološka analiza. Taksonomska analiza ukazuje da golosjemenjača ima 2 vrste (1,08 %), dvosupnica 155 vrsta (83,33 %), a jednosupnica 29 vrsta (15,59 %). Analiza životnih oblika pokazuje da su najviše zastupljeni hemikriptofiti sa 113 vrsta (60,75 %)i terofiti s 29 vrsta (15,59 %). U fitogeografskoj analizi dominiraju biljke euroazijskog flornog elementa sa 63 vrste (33,87 %) i biljke široke rasprostranjenosti s 38 vrsta (20,43 %). Fitocenološka analiza florističkog sastava pokazuje da ovi travnjaci čine prijelazni položaj između razreda Festuco-Brometea i Molinio-Arrhenatheretea, odnosno da pokazuju prijelazni položaj između redova Festucetalia valesiacae, Brometalia erecti i Arrhenatheretalia.