Jana Niedobová

Sublethal effect of agronomical surfactants on the spider Pardosa agrestis

In addition to their active ingredients, pesticides contain also additives - surfactants. Use of surfactants has been increasing over the past decade, but their effects on non-target organisms, especially natural enemies of pests, have been studied only very rarely. The effect of three common agrochemical surfactants on the foraging behavior of the wolf spider Pardosa agrestis was studied in the laboratory. Differences in short-term, long-term, and overall cumulative predatory activities were investigated. We found that surfactant treatment significantly affected short-term predatory activity but had no effect on long-term predatory activity. The surfactants also significantly influenced the cumulative number of killed prey. We also found the sex-specific increase in cumulative kills after surfactants treatment. This is the first study showing that pesticide additives have a sublethal effect that can weaken the predatory activity of a potential biological control agent. More studies on the effects of surfactants are needed to understand how they affect beneficial organisms in agroecosystems.

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.

Patterns of functional diversity of two trophic groups after canopy thinning in an abandoned coppice

Coppice abandonment had negative consequences for the biodiversity of forest vegetation and several groups of invertebrates. Most coppicing restoration studies have focused only on a single trophic level despite the fact that ecosystems are characterized by interactions between trophic levels represented by various groups of organisms. To address the patterns of functional diversity in the perspective of coppicing restoration, we studied the short-term effects of conservation-motivated tree canopy thinning in an abandoned coppice with standards in Central Europe, a region where such attempts have been rare so far. The functional diversity of vascular plants and spiders, chosen as two model trophic groups within the forest ecosystem, was compared between thinned and control forest patches. To characterize functional patterns, we examined several functional traits. These traits were assigned to two contrasting categories: response traits reflecting a change of environment (for both vascular plants and spiders) and effect traits influencing the ecosystem properties (only for vascular plants). Functional diversity was analysed by CCA using two measures: community-weighted means (CWM) and Rao’s quadratic diversity (RaoQ). CCA models revealed that the canopy thinning had a positive effect on the diversity of the response traits of both trophic groups and negatively influenced the diversity of effect traits. In addition, we found distinct seasonal dynamics in functional diversity of the spider communities, which was probably linked to leaf phenology of deciduous trees. We conclude that canopy thinning affected functional diversity across trophic groups during the initial phase of coppicing restoration. With necessary precautions, careful canopy thinning can be effectively applied in the restoration of functional diversity in abandoned coppices.

Effects of glufosinate-ammonium herbicide and pod sealant on spider Pardosa agrestis

Herbicides based upon glufosinate‐ammonium (GLA) are among the worlds most widely used. They also are applied on the most prominent oil crops as desiccants in combination with pod sealants to prevent pod shatter and seed loss close to harvest. Even though these crops occupy a significant part of the worlds agroecosystems, the effects of GLA herbicides on non‐target arthropods, and in particular natural enemies of pests, have been studied very rarely, and such effects of pod sealants have never been studied. We studied in our laboratory mortality as well as prey capture efficiency of the common GLA herbicide and desiccant Basta 15®, pod sealant Arrest®, and a mixture of both on the wolf spider Pardosa agrestis. We found that Basta 15® and the mixture had lethal effect on spiders. We also found significant, short‐term effect on predatory activity of spiders after all treatments. Basta 15® significantly influenced the amount of captured prey also in the long term. This is the first study showing lethal effect on spiders of the herbicide and herbicide plus pod sealant mixture. This is also the first study examining the effects of pod sealant on the mortality and predatory activity of a pest antagonist. More studies regarding the effects of agricultural chemical mixes are needed to uncover their effects on beneficial organisms existing within agroecosystems.

Effect of adjacent steppe-like habitats on spider diversity in vine plants

Spiders are important natural enemies of pests in many agroecosystems. Spiders’ diversity and abundance—and therefore their biological control potential—often increases with the presence of non-crop habitats adjacent to the agroecosystem and/or the abundance of such habitats in the landscape. This research aims to determine whether spider communities dwelling on vine plant trunks are richer and more abundant in terraced vineyards than in plain vineyards. We found that spiders’ abundance and species richness were significantly greater during part of the season in the plain than the terraced types of vineyards. The abundance of spiders on the vine plants in the terraced vineyards decreased gradually from the field margins to the centre while no such pattern was observed in the plain vineyards. Subsequent experiments will be needed in order to elucidate the role of the individual mechanisms and parameters that underpin our findings. For example, the air flow (direction and intensity), the presence of the predators, heterogeneity and the presence of shrubs on the slopes of terraces should be studied further. Particularly, because our findings contradict the general assumption that terraced vineyards should host richer spider communities.