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The overuse of insecticides to control vector insects such as Diaphorina citri Kuwayama in citrus groves has altered the population dynamics of pest mites. Among phytophagous mites, population outbreaks of citrus leprosis mite, Brevipalpus yothersi Baker, have been increasingly intense and frequent in Brazilian citrus groves. Despite the great importance of the B. yothersi mite for citrus production, the lethal and sublethal effects of insecticides on this mite have not yet been studied. Therefore, in this study, the effects of insecticides commonly used for D. citri control on B. yothersi mortality, reproduction, and instantaneous growth rate were assessed. For this, two experiments were carried out, one under controlled conditions and another in a greenhouse. The insecticides tested were beta-cyfluthrin, bifenthrin, buprofezin, chlorpyrifos, dimethoate, pyriproxyfen, and thiamethoxam at 0 (control), 0.0625, 0.125, 0.25, 0.5, 1, and twofold the recommended insecticide concentration for D. citri control. The pyriproxyfen insecticide provided high mortality of B. yothersi even at low concentrations. Furthermore, this insecticide negatively interfered with the reproduction of this mite. Beta-cyfluthrin, bifenthrin, buprofezin, chlorpyrifos, dimethoate, and thiamethoxam, in the tested concentrations, showed low impact on citrus leprosis mite. Regarding the reproduction of the mite, no significant increase in fecundity was observed on B. yothersi females exposed to insecticide residues, regardless of the concentration tested. Therefore, the application of these insecticides in the management of pest insects is unlikely to promote an increase in the citrus leprosis mite population.
相似文献Winter is a challenging period for aquatic research—weather is uncomfortable, ice is hazardous, equipment fails, and daylength is short. Consequently, until recently relatively little research on freshwater fishes has included winter. Telemetry methods for tracking fish and observing movement behavior are an obvious solution to working in harsh conditions because much of the data can be collected remotely, and passive methods collect data year-round without winter maintenance. Yet, many telemetry studies do not collect data during winter or, if they do, only report data from the ice-free seasons while the remaining data are unused. Here, we briefly summarize the advantages and limitations of using telemetry methods in winter, including acoustic and radio telemetry and passive integrated transponder technology, then review the range of questions related to fish ecology, behavior, bioenergetics, and habitat use that can be addressed in winter using telemetry. Our goals are to highlight the untapped potential of winter fish biology and to motivate scientists to revisit their four-season telemetry data and incorporate objectives specific to winter biology in future study plans.
相似文献Niche partitioning occurs among coexisting populations to reduce the effects of competitive exclusion among species of similar niche. The aim of the present study is to verify the trophic niche partitioning and feeding behavior between two mustelids, the Giant otter and the Neotropical otter, through the dry and rainy season hydrologic of the Lower Xingu River. Our results suggest that the diets of both mustelids are composed primarily of fish of the family Anostomidae (Headstanders). Despite extensive niche overlap, our results indicate partitioning is facilitated by differences in niche breadth, with potential implications for conservation of both species in the case of declines in prey abundance and diversity. Both species inhabit an area recently impacted by completion of the Belo Monte Hydropower Plant, resulting in large changes to the hydrologic regime. Thus, our results provide important information for conservation efforts regarding the feeding behavior and co-occurrence of both species, as well as providing a baseline for monitoring future health of these mustelid populations. The present study is the first to test the hypothesis of niche partitioning between these two mustelids outside a protected area in the Amazon.
相似文献The production and release of chemical compounds by invasive plants can affect competitors and native species overall, destabilizing ecological interactions and harming ecosystem functioning. Hedychium coronarium is an invasive macrophyte common on Brazilian riparian areas that produces a wide variety of allelochemicals, but little is known about their effect on aquatic species. Here, we identified the major chemical compounds of the aqueous extract of H. coronarium rhizomes and assessed its toxicity, evaluating the growth inhibition of one alga (Raphidocelis subcapitata) and one macrophyte (Lemna minor), and the lethality of cladoceran (Ceriodaphnia silvestrii and Daphnia similis) and Chironomidae larvae (Chironomus sancticaroli). The majoritarian compounds of H. coronarium rhizomes were Coronarin D and Coronarin D Ethyl Ether. The aqueous extract was toxic for all tested species. We observed growth inhibition in R. subcapitata, as well as reduction in biomass in L. minor. Chironomus sancticaroli and cladoceran were the most sensible species. The aqueous extract of H. coronarium rhizomes was toxic on tested conditions, suggesting that the rhizome compounds may interfere on aquatic organisms and in the dynamic of trophic webs of aquatic ecosystems on invaded areas.
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