An Edge Effect Caused by Adult Corn-Rootworm Beetles on Sunflowers in Tallgrass Prairie Remnants

Abstract: The once-extensive tallgrass prairie community of North America has been reduced to small remnants, many of which are surrounded by intensive corn (   Zea mays ) agriculture. We investigated adult corn-rootworm beetles (Chrysomelidae : Diabrotica spp.), important pests of corn, on sunflowers (Asteraceae : Helianthus spp . ) in prairie remnants in southeast Minnesota. Large numbers of beetles invaded the prairie from surrounding corn fields in late summer. D. barberi and D. virgifera were captured on sticky traps in all locations in the prairie, but abundance was much greater near the edge adjacent to corn. We observed D. barberi ( but not D. virgifera ) feeding extensively on sunflower pollen and occasionally on other flower parts, such as petals. Sunflowers located nearer corn fields sustained more floral damage than those farther from corn. To determine the effect of beetle damage on seed set, we enclosed sunflower heads in bags with either zero, two, or four D. barberi adults. Seed set was reduced in heads enclosed with D. barberi . Thus, this agricultural pest may interfere with the successful reproduction of sunflowers and possibly other prairie composites that flower in late summer. Given the small size of most prairie remnants and the abundance of this flower-feeding beetle in landscapes dominated by corn agriculture, D. barberi may affect the sustainability of prairie plant populations.     

Comparison of translocation methods to conserve metallophyte communities in the Southeastern D.R. Congo

In southeastern Democratic Republic of Congo, unique metallophyte communities supporting numerous endemic species occurred on the highly mineralized copper cobalt (Cu–Co) hills throughout the province. These hills are economically valuable mineral reserves; mining activities represent therefore a threat to the long-term persistence of these communities. Ex situ conservation program was set up by a mining company to rescue and conserve the diversity of Cu–Co communities until restoration activities are initiated. Two kinds of Cu–Co communities: the steppe and the steppic savanna, were translocated using topsoil spreading and whole-turf translocation. In this study, we assessed the effectiveness of these two techniques in conserving Cu–Co communities and their potential use in future restoration programs. More than 2 years after the translocation, whole-turf translocation appeared to be the better technique for ex situ conservation of endemic Cu–Co species. Not only did whole-turf successfully translocate numerous target species that were not present in the topsoil areas, but it also resulted in fewer ruderal and non-target species compared to topsoil spreading. Topsoil spreading recorded low seedling emergence from seed bank due to large proportions of dormant seeds or the absence of a seed bank, especially for the steppic savanna. Restoration of the steppe is currently more successful than for steppic savanna where the lack of dominant and structuring species likely contributed to divergence in species composition compared to reference ecosystem. Our study stresses the fact that tropical old-growth grasslands, which require probably several centuries to assemble, are difficult to restore or translocate.     

Oxidoreductases provide a more generic response to metallic stressors (Cu and Cd) than hydrolases in soil fungi: new ecotoxicological insights

The present study investigates the effect of metals on the secretion of enzymes from12 fungal strains maintained in liquid cultures. Hydrolases (acid phosphatase, β-glucosidase, β-galactosidase, and N-acetyl-β-glucosaminidase) and ligninolytic oxidoreductases (laccase, Mn, and lignin peroxidases) activities, as well as biomass production, were measured in culture fluids from fungi exposed to Cu or Cd. Our results showed that all fungi secreted most of the selected hydrolases and that about 50 % of them produced a partial oxidative system in the absence of metals. Then, exposure of fungi to metals led to the decrease in biomass production. At the enzymatic level, Cu and Cd modified the secretion profiles of soil fungi. The response of hydrolases to metals was contrasted and complex and depended on metal, enzyme, and fungal strain considered. By contrast, the metals always stimulated the activity of ligninolytic oxidoreductases in fungal strains. In some of them, oxidoreductases were specifically produced following metal exposure. Fungal oxidoreductases provide a more generic response than hydrolases, constituting thus a physiological basis for their use as biomarkers of metal exposure in soils.     

Sublethal effects of epoxiconazole on the earthworm <Emphasis Type="Italic">Aporrectodea icterica</Emphasis>

Earthworms play a key role in agroecosystem soil processes. This study aims to assess the effects of different doses of a commercial formulation of epoxiconazole (Opus®), a persistent and widely used fungicide, on the earthworm Aporrectodea icterica. A laboratory study was conducted in a natural soil in order to measure effects of Opus® on earthworm mortality, uptake, weight gain, enzymatic activities (catalase and glutathione-S-transferase), and energy resources (lipids and glycogens). The estimated LC50 was 45.5 mg kg^?1, or 268 times the recommended dose. Weight gains were 28, 19, and 13 % of the initial weight after 28 days of exposure in the control and D1 and D10 (1 and 10 times the recommended dose) treatments, respectively. No difference was observed for catalase activity between the three treatments, at 7, 14, or 28 days. The glutathion-S-transferase (GST) activity was two times as high in D1 as in D0 at 14 days. At 28 days, glycogen concentration was lower in D10 than in the D1 treatment. This study highlighted moderate sublethal effects of the commercial formulation Opus® for earthworms. Considering that these effects were observed on a species found in cultivated fields, even at recommended rates, much more attention should be paid to this pesticide.     

Secretion profiles of fungi as potential tools for metal ecotoxicity assessment: a study of enzymatic system in Trametes versicolor

The relationship between the expression of extracellular enzymatic system and a metal stress is scarce in fungi, hence limiting the possible use of secretion profiles as tools for metal ecotoxicity assessment. In the present study, we investigated the effect of Zn, Cu, Pb and Cd, tested alone or in equimolar cocktail, on the secretion profiles at enzymatic and protein levels in Trametesversicolor. For that purpose, extracellular hydrolases (acid phosphatase, β-glucosidase, β-galactosidase and N-acetyl-β-glucosaminidase) and ligninolytic oxidases (laccase, Mn-peroxidase) were monitored in liquid cultures. Fungal secretome was analyzed by electrophoresis and laccase secretion was characterized by western-blot and mass spectrometry analyses. Our results showed that all hydrolase activities were inhibited by the metals tested alone or in cocktail, whereas oxidase activities were specifically stimulated by Cu, Cd and metal cocktail. At protein level, metal exposure modified the electrophoretic profiles of fungal secretome and affected the diversity of secreted proteins. Two laccase isoenzymes, LacA and LacB, identified by mass spectrometry were differentially glycosylated according to the metal exposure. The amount of secreted LacA and LacB was strongly correlated with the stimulation of laccase activity by Cu, Cd and metal cocktail. These modifications of extracellular enzymatic system suggest that fungal oxidases could be used as biomarkers of metal exposure.     

Contrasted tolerance of Agrostis capillaris metallicolous and non-metallicolous ecotypes in the context of a mining technosol amended by biochar,compost and iron sulfate

Environmental Geochemistry and Health - Metal(loid) contamination of soil, resulting from the mining activities, is a major issue worldwide, due to its negative effects on the environment and...     

Effects of biochar,ochre and manure amendments associated with a metallicolous ecotype of Agrostis capillaris on As and Pb stabilization of a former mine technosol

Environmental Geochemistry and Health - Metal(loid) soil pollution is a major environmental and health issue, requiring these areas to be remediated, for example through phytoremediation processes....