Michaela Kolářová

Weed vegetation of arable land in the Czech Republic: environmental a management factors determining weed species composition

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 relevés that were 100 m2 in size, placed in the central part of fields. In total, 202 relevés 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.

The effect of eight common herbicides on the predatory activity of the agrobiont spider Pardosa agrestis

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.

Organic, integrated and conventional management in apple orchards: effect on plant species composition, richness and diversity

The study was conducted to assess the eff ect of conventional, integrated and organic management on diff erences in plant species composition, richness and diversity. The plants were studied in triads of orchards situated in three regions of the Czech Republic. Data about species occurrences were collected on 15 permanent plots in the tree rows and 15 plots between tree rows in each of the apple orchards during 2009. A total of 201 vascular plant species (127 native species, 65 archaeophytes, and 9 neophytes) were found. Management type and also diff erent regional conditions had a signifi cant eff ect on plant species composition and on diversity parameters of orchard spontaneous vegetation. Species richness and species pool was signifi cantly higher in the organic orchards than in the diff erently managed orchards. Management type had signifi cant eff ect on proportions of archaeophytes, and also neophytes in apple orchards.

Disruption of the chemical communication of the European agrobiont ground-dwelling spider Pardosa agrestis by pesticides

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 pyrethroïd‐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 males ability to detect the silk cues of the female.

Changes in weed community composition in a long-term trial with different crop rotations and herbicide treatments

The impact of herbicide application on weed community changes was studied in a long-term field experiment conducted since 1972 at two sites in the Czech Republic; Pernolec and Hněvceves. The ongoing trial comprises multi-crop and simple crop rotations with 50 and 75% cereals, respectively. Three herbicide treatments were used: (1) untreated; (2) synthetic auxins (MCPA; 2,4-D; only in simple crop rotation) and (3) targeted herbicide combinations, including especially sulfonylureas, triazines, ureas and synthetic auxins. Weed species composition and weed density were assessed at the trial beginning, during the trial and in the present (2013- 2016). Changes in weed flora composition were found out. In Hněvceves, abundance of some species such as Galium aparine, Stellaria media, and Vicia spp. increased on untreated plots; the abundance of Apera spica-venti, Fumaria officinalis, and Tripleurospermum inodorum increased on treated plots. In Pernolec, some species receded in all variants, e.g. Myosotis arvensis, Raphanus raphanistrum, and Scleranthus annuus; the abundance of Centaurea cyanus, Tripleurospermum inodorum, Veronica spp., and Spergula arvensis increased in untreated plots. No significant differences affected by time and treatment were detected in population densities of Apera spica-venti, Arabidopsis thaliana, and Stellaria media. The species composition of the weed community was affected by explanatory variables in the following order: treatment < time < type of cultivated crop. The longterm study confirmed weed population shifts over time were caused by interaction between the management factors and environmental conditions.

Effects of adjuvants and carriers on propoxycarbazone and pyroxsulam efficacy on Bromus sterilis in winter wheat

Bromus species are annual winter weeds from the Poaceae family which have become troublesome weeds of winter cereals. The herbicides propoxycarbazone and pyroxsulam are widely used for control of B. sterilis. The objective of this study was to determine the effect of different types of adjuvants and carriers on the efficacy of pyroxsulam and propoxycarbazone on B. sterilis. Small plot field trials were carried out in North Bohemia, Central Europe during 2011–2013. The tested carriers and adjuvants affected the efficacy of both herbicides and the seed production of B. sterilis. Urea ammonium nitrate was a less effective carrier than water (differences 5–30%). The most effective adjuvant was methylated seed oil (MSO), whose addition into the application water solution increased the herbicide efficacy of propoxycarbazone by 5–35%. Efficacy of the herbicide pyroxsulam was increased by adjuvant MSO by 10–30%. Nonionic surfactant increased herbicide efficacy only in 2013 (by 17%). Effect of organosilicone surfactant on the herbicide efficacy was negative (lower efficacy). Seed production of B. sterilis on untreated plots ranged between 20 000 and 50 000 seeds/m2 in experimental years. Seed production was the lowest on plots treated by the herbicide plus MSO (1300–4500 seed/m2).

One generalist or several specialist species? Wide host range and diverse manipulations of the hosts’ web-building behaviour in the true spider parasitoid Zatypota kauros (Hymenoptera: Ichneumonidae)

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.