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Three plot field trials (2014–2017) were carried out in Prague. The aim of the study was to evaluate the efficacy of herbicides against volunteers from Clearfield® (CL) and conventional oilseed rape (Brassica napus L.) in winter wheat (Triticum aestivum L.) and to quantify the effect of herbicide and application time on wheat yield. Autumn control (diflufenican, isoproturon, flumioxazin, metribuzin, penoxsulam, florasulam, chlorsulfuron were tested) of volunteer oilseed rape (OSR) was more effective than using the spring herbicide treatments (2,4-D, iodosulfuron, amidosulfuron, tritosulfuron, florasulam), especially against the CL OSR variety. Full control of both CL and conventional OSR was recorded only on plots treated by the combination of metribuzin + diflufenican + flufenacet. The most effective spring herbicide was 2,4-D, but its efficacy (82–95%) depended on the growth stage of OSR and application rate. Efficacy of spring herbicides against CL OSR was lower compared to that against conventional OSR, but there were large differences among tested herbicides. Efficacy of tested ALS inhibitors against volunteer CL OSR ranged between 20% (chlorsulfuron) and 77% (tritosulfuron + florasulam). Seed production of volunteer OSR ranged between 0 and 37,000 seeds m−2 while depending strongly on time of sowing and weather conditions during the autumn and winter. No seed of CL OSR matured on plots treated by metribuzin in autumn or 2,4-D at application rate 377 g ha−1 in spring. Volunteer OSR in competition with winter wheat caused almost 50% wheat yield loss on the untreated check. Although the efficacy of most spring herbicide treatments on conventional OSR was good, the competition effect of OSR on wheat during winter and early spring caused about 0.52–0.86 t ha−1 greater yield loss compared to autumn herbicide treatments.

Precipitation and irrigation strongly affect herbicide management of vegetables, especial fast- growing vegetables as a kohlrabi. The objective of this study was to compare the effects of irrigation and paraffin oil-based soil adjuvant on the efficacy and selectivity of pendimethalin and metazachlor herbicides and their tank-mix combination in kohlrabi. Small plot experiments were carried out in Prague, Czech Republic during 2015 and 2016. Herbicide efficacy on Chenopodium album, Mercurialis annua, and Solanum physalifolium was significantly affected by irrigation shortly after herbicide application, but the efficacy, visual phytotoxicity, as well as both aboveground and root kohlrabi biomass were not affected by the adjuvant. Pendimethalin caused significantly greater phytotoxicity than did metazachlor. Aboveground biomass of kohlrabi plants treated with pendimethalin was about 20–50% less compared to that of plants grown on hand-weeded plots, similar as a tuber yield (tuber weight was about 30% lower). Heavy irrigation shortly after the application of pendimethalin did not affect selectivity of this herbicide treatment. On the contrary, selectivity of metazachlor was strongly affected by irrigation and natural precipitation. Weight of tubers harvested on plots treated by pendimethalin was the same or lower compared to that from plots with competition of annual weeds. The lowest yield (50% compared to hand-weeded check) was on the plots treated by herbicide mixture pendimethalin + metazachlor and irrigated shortly after the application.

Parasitoid wasps of the Polysphincta genus-group are highly specialised on their spider hosts, and most of them are known to manipulate their hosts into building a special web in which the parasitoid pupates. Trophic niche and the plasticity of host use were investigated in the koinobiont parasitoid Zatypota kauros Gauld from Queensland, Australia. We found that Z. kauros attacks spider hosts from different families, each differing widely in their web-building behaviours, which makes it unique in the breadth of its host range. Molecular analyses revealed that the taxon Z. kauros contains three divergent mitochondrial lineages. Lineage A was associated exclusively with spiders of the genus Anelosimus (Theridiidae), which builds tangle webs; lineage B was associated with the genus Cyrtophora (Araneidae), which weaves tent webs; and lineage C was associated with a broad range of hosts, including spiders of both the families Araneidae and Theridiidae. Unique host manipulations could be observed in the web-building behaviours of the different host groups. Nevertheless, nuclear data from two ribosomal genes and three introns did not add any support to the existence of different evolutionary lineages, nor did they coincide with the different host groups. The partial correspondence of mitochondrial lineage and host use, together with an apparent mito-nuclear conflict might indicate maternal effects or very recent and/or incomplete speciation in this taxon. Given their wide host range and intriguing interactions with their hosts, the Z. kauros complex represents a promising system for studying parasitoid specialisation and its potential impact on speciation.

Polysphinctine wasps are exclusive parasitoids of spiders and their host utilisation strategies are highly taxonomically specific. In this study, the host utilisation of two Australasian parasitoid wasps of the genus Eriostethus was studied for the first time. Our study revealed considerable differences in host-parasitoid interactions between Eriostethus minimus associated with 3D tangle web-building spiders from the family Theridiidae (new family record for Eriostethus) and E. perkinsi associated with 2D orb-web weaving spiders from the family Araneidae. A pupa of the former species was located in a spider retreat in the centre of an unmodified 3D tangle web and the pupal cocoon had a sparsely woven and partially transparent wall. In contrast, a cocoon of the latter species was suspended at the centre of a modified irregular sparse 3D cocoon web and the pupal cocoon had a strong, densely woven cocoon wall. This difference in host utilisation is not in agreement with the synonymisation of Millironia with Eriostethus.

The impact of eight herbicides in different residual stages on the predatory activity of a potential biological control agent, the wolf spider Pardosa agrestis, was studied in the laboratory. We found that fresh wet residues of all tested herbicides negatively affected the total and cumulative predatory activity of this species. Moreover, treatment with 48-h-old residues of the glufosinate ammonium herbicide Basta induced a significant increase in predatory activity in P. agrestis, presumably as a consequence of hormesis. These results imply that the natural pest control provided by the agrobiont spider P. agrestis can be weakened by the application of the studied herbicides. On the basis of our results, we suggest that sublethal effects on beneficial organisms should be considered in the planning of weed management of agroecosystems and should not be omitted from the herbicide registration process.

Lycosid spiders are among the most abundant and diverse insectivores occurring in all agroecosystems. Certain pest management practices, such as the application of pesticides, can disrupt their role in insect pest control. Therefore, understanding the effects of pesticides, including sublethal effects, is essential for the assessment of chemical effects on beneficial arthropods. We investigated the sexual chemical communication of the beneficial agrobiont spider Pardosa agrestis and its disruption by two widely used pesticides, the glyphosate-based herbicide Roundup and the pyrethroid-based insecticide Nurelle D. A two-choice olfactometer and Y-maze were used to study the effectiveness of female airborne and dragline pheromone cues and the disruptive effect of the pesticides. Males of P. agrestis did not locate females via airborne cues, but were very receptive to female dragline silk and male dragline silk. When both female dragline silk and male dragline silk were provided at the same time, the males preferred female silk. Pesticide treatments significantly affected the male ability to follow female cues deposited on dragline silk. The 3-h residues of both Roundup and Nurelle D significantly disrupted the male ability to follow female cues deposited on dragline silk. Treatment by 48-h residues significantly disrupted the male ability only in the case of Nurelle D. Our results demonstrate that pesticides reduce the ability of male spiders to search for a mate due to the disruption of the male's ability to detect the silk cues of the female.

The main aim of the present study was to evaluate benefits of the new technology of sugar beet varieties tolerant to foramsulfuron (FSN) + thiencarbazone-methyl (TCM) herbicides commercialised as Conviso® Smart (four weed management strategies were tested) compared to conventional herbicides (two weed management strategies). Plot-field trials were carried out in Prague (Czech Republic) in 2016–2019. Efficacy on Chenopodium album L., Amaranthus retroflexus L., Echinochloa crus-galli (L.) P. B., Abutilon theophrasti Med. and weed beet were evaluated. FSN + TCM controlled all tested weeds very well (efficacy more than 97%) in case of split application with an oil adjuvant. When only one application of FSN + TCM was performed in dry weather conditions, efficacy on C. album and A. theophrasti was insufficient (less than 90%). FSN + TCM fully controlled weed beet at all tested weed management strategies in all experimental years and a residual activity of this herbicide did not allow new plants to emerge. The conventional tank-mixes (TM) controlled C. album and A. retroflexus well (efficacy more than 96%). Efficacy of conventional TM on E. crus-galli ranged from 78 to 100%. Efficacy on A. theophrasti was affected by herbicides used and weather conditions, but did not exceed 92% with either of the conventional TM. The tested conventional herbicides were not able to control weed beet. A relatively high reproductive ability of C. album and A. retroflexus (13,000–157,000 and 7000–10,000 seeds m−2, respectively) was seen in plots where these weeds were not fully controlled. The seed production of A. theophrasti was relatively low (not exceeded 25,000 seeds m−2). However, mature seeds were present in most plots. The reproductive ability of E. crus-galli in sugar beet canopy was much lower (200 - 1800 seeds m−2) compared to the other species, due to its late emergence. Weed beet competed with sugar beet only when other weeds were controlled and weed beet survived the treatment. In these plots, fruit production of weed beet was significantly higher (5000–75,000 fruits m−2). The highest sugar beet yields (78–100 t ha−1) were in weed-free plots or plots with a low weed infestation (split application of FSN + TCM). A significantly lower yield (45–52 t ha−1) was recorded when C. album and A. theophrasti were not sufficiently controlled. In plots where the weed beet was the only weed not controlled, sugar beet yield ranged from 23 to 61 t ha−1. The lowest sugar beet yield (less than 10 t ha−1) was observed in untreated plots where mainly C. album and A. theophrasti predominated. There was a negative relationship between sugar beet yield and total weed biomass.

This paper reports on the current situation in weed vegetation composition on arable land in selected areas of the Czech Republic, assessment of influence of selected variables: applied management systems (conventional, organic), crops (winter cereals, root crops) and altitude and ranking of the importance of these particular factors. A phytocoenological survey was conducted from 2006 to 2008 during a vegetation period using releves that were 100 m 2 in size, placed in the central part of fields. In total, 202 releves of agricultural vegetation were recorded. The combined environmental variables explained 10.6% of the variability. Based on the pCCAs, the highest effect was found at altitude, which explains 5.1% of the species composition variability. The second and third most significant factors are crop and management system, which explain 3.3% and 1.8% of the variability, respectively. The lowlands were generally characterised by the thermophilous summer annual weed species. The higher altitudes were populated by species that are typical for colder areas and poor, humid, and acidic soil types, such as cambisoil.

Summary This article documents the impact of site conditionsand farming practices on the occurrence of rare andendangered weeds on arable land in the Czech Republic.A survey was conducted between 2006 and 2008 inwinter cereals, spring cereals and wide-row crops. Therelationship between the occurrence of plants andexplanatory factors was analysed using a multivariateanalysis to calculate species frequencies in differenttypes of farming, crops and altitudes. In total, 290releves were recorded, with a total number of 172weed species. Nineteen weeds, classified as rare andendangered species according to the national Czechlist, were identified in 106 releves. The highest effecton the occurrence of rare and endangered weed specieswas observed for altitude. Almost half of the recordedendangered and rare species belonged to thethermophilous weed vegetation typical for cereals onbasic soils. A higher occurrence of endangered spe-cies has been confirmed for organic farming, wherethe sum of frequencies was 4.5 times higher than inconventional farming. Field size was not included inour analyses, but could be a factor affecting weedassemblages. The highest frequency of rare specieswas recorded in spring cereals, followed by wintercereals and wide-row crops. Higher numbers wereidentified within fields with higher weed coverage.Lower farming intensity and diversified farming sys-tems at higher altitudes provided better conditionsfor the occurrence of rare species than intensivelyfarmed lowlands.Keywords: red list species, conventional farming,organic farming, altitude, crop, syntaxon, frequency,weed cover.K

This paper reports on the within-habitat (α) and on the between-habitat (β) diversity of weed vegetation on arable land in the Czech Republic, influenced by management systems, crops grown and altitude. A phytocoenological sur vey was conducted from 2006 to 2008 during a vegetation period using releves that were 100 m 2 in size, placed in the central part of fields. The species richness and the mean Sorensen dissimilarity were calculated. The statistically sig nificant effects of the type of farming and altitude on species richness were recorded. The average species numbers in one releve reached 9.17 and 21.17 in conventional and organic farming, respectively. In both management systems, an increasing number of species was recorded with increasing altitude. Statistically significant effects of all the vari ables were observed when evaluating β-diversity. Higher β-diversity was found in conventional farming.