Dispersal of aphids, whiteflies and their natural enemies under photoselective nets

Integrated Pest Management of insects includes several control tactics, such as the use of photoselective nets, which may reduce the flight activity of insects. Limiting the dispersal of pests such as aphids and whiteflies is important because of their major role as vectors of plant viruses, while a minor impact on natural enemies is desired. In this study, we examined for the first time the dispersal ability of three vector species, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae) and Myzus persicae (Sulzer) (Hemiptera: Aphididae), in cages covered with photoselective nets. Contrary to the results obtained with aphids, the ability of the whitefly B. tabaci, to reach the target plant was reduced by photoselective nets. In a second set of experiments, the impact of UV-absorbing nets on the visual cues of two important predator species, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), was evaluated. The anthocorid was caught in higher numbers in traps placed under regular nets, whereas the mites preferably chose environments in which the UV radiation was attenuated. We have observed a wide range of effects that impedes generalization, although photoselective nets have a positive effect on pest management of whiteflies and aphids under protected environments.     

Hunting management in relation to profitability aims: red-legged partridge hunting in central Spain

Game management is widely implemented in Spain, affecting more than 70?% of land cover. Management intensity may be linked to the financial aims of hunting estates, but no study of these aspects has been developed in Spain, where commercial hunting is common. Through interviews with game managers and field surveys, we quantified physical and economic traits, management techniques, and hunting methods in a sample of 59 small-game hunting estates located in south-central Spain (where red-legged partridge hunting has the highest socioeconomic importance in the country). We compared non-commercial estates (aimed for leisure, managed mainly by local hunting societies) and commercial estates (aimed at financial benefit); among the latter, we also assessed “intensive” estates (a special category of commercial estates licensed to release farm-reared partridges without temporal or numerical limits throughout the hunting season). Commercial estates had more intensive management, including more and larger partridge releases, higher density of supplementary feeders and more intensive predator control. Thus, any positive or negative effects on biodiversity of these management techniques would be higher in commercial than in non-commercial estates. Commercial estates also retained more natural vegetation, which may help to enhance the landscape and biodiversity value of farmland in central Spain. On the other hand, differences in management and hunting styles were most marked between intensive and other type of estates (both commercial and non-commercial); this indicates that intensive estates are qualitatively different from other small-game estates, both ecologically (hunting based on releases and driven shooting) and economically (higher inputs and outputs). It would be desirable to find ways to quantify the environmental or social costs and benefits of different management techniques, and integrate them in the economics of hunting estates.     

Kestrel-Prey Dynamic in a Mediterranean Region: The Effect of Generalist Predation and Climatic Factors

Background

Most hypotheses on population limitation of small mammals and their predators come from studies carried out in northern latitudes, mainly in boreal ecosystems. In such regions, many predators specialize on voles and predator-prey systems are simpler compared to southern ecosystems where predator communities are made up mostly of generalists and predator-prey systems are more complex. Determining food limitation in generalist predators is difficult due to their capacity to switch to alternative prey when the basic prey becomes scarce.

Methodology

We monitored the population density of a generalist raptor, the Eurasian kestrel Falco tinnunculus over 15 years in a mountainous Mediterranean area. In addition, we have recorded over 11 years the inter-annual variation in the abundance of two main prey species of kestrels, the common vole Microtus arvalis and the eyed lizard Lacerta lepida and a third species scarcely represented in kestrel diet, the great white-toothed shrew Crocidura russula. We estimated the per capita growth rate (PCGR) to analyse population dynamics of kestrel and predator species.

Principal Findings

Multimodel inference determined that the PCGR of kestrels was better explained by a model containing the population density of only one prey species (the common vole) than a model using a combination of the densities of the three prey species. The PCGR of voles was explained by kestrel abundance in combination with annual rainfall and mean annual temperature. In the case of shrews, growth rate was also affected by kestrel abundance and temperature. Finally, we did not find any correlation between kestrel and lizard abundances.

Significance

Our study showed for the first time vertebrate predator-prey relationships at southern latitudes and determined that only one prey species has the capacity to modulate population dynamics of generalist predators and reveals the importance of climatic factors in the dynamics of micromammal species and lizards in the Mediterranean region.     

Effects of pesticides commonly used in peach orchards in Brazil on predatory lacewing <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> under laboratory conditions

Effects of the maximum field recommended concentration of five pesticides currently used on peaches in Brazil; abamectin, deltamethrin, methoxyfenozide, phosmet and trichlorfon were tested on the predator Chrysoperla carnea (Stephens) (Neuroptera, Chrysopidae). Dimethoate was used as positive standard. Three analytical laboratory tests, based on IOBC—working group pesticides and beneficial organisms guidelines were used: (1) exposure to fresh pesticide residue on glass plates of (a) larvae (susceptible life stage) and (b) adults (less susceptible life stage); (2) direct spraying of eggs and pupae; (3) exposure of larvae and adults to pesticide residues on plant leaves at different intervals after application (persistence). In tests 1, abamectin was slightly harmful to C. carnea larvae and phosmet and trichlorfon were slightly harmful and moderately harmful to C. carnea adults, respectively. After direct spraying of eggs and pupae, all the pesticides were harmless. In the persistence tests, abamectin and trichlorfon were classified as short lived and therefore they could be considered for use in Integrated Pest Management (IPM) programs under special conditions (i.e. reduced direct contact). Phosmet, however, caused between 56.3 and 75.0% mortality up to 30 days after treatment and it was rated as persistent. No sublethal effects were detected in the reproductive behaviour of adults (fecundity and fertility) compared with the control in any treatment. In conclusion, the insecticides with little or no toxicity to C. carnea such as abamectin, deltamethrin and methoxyfenozide could be considered as IPM-compatible, subject to further field studies.     

Inhibition of Cdk4 activity enhances translation of p27kip1 in quiescent Rb-negative cells

We show in this work that the inhibition of Cdk4 (6) in Rb(-/-) 3T3 cells enhances the accumulation of the p27(kip1) cyclin-dependent kinase inhibitor when these cells are induced into quiescence. Two different forms of inhibition of Cdk4 (6), namely overexpression of the Cdk4 (6) inhibitor p16 and overexpression of a dominant negative mutant of Cdk4 (Cdk4(N158)), result in this effect. This suggests that the relevant activity of Cdk4 (6) that has to be inactivated in this setting is its kinase activity. The accumulation of p27(kip1) is due to enhanced translation of the protein, mediated by the 3'-untranslated region of the p27(kip1) mRNA. Moreover, the cells that overexpress p16(ink4a) or Cdk4(N158) show a delay in G(1) when made quiescent and restimulated to proliferate. This delay is overcome by transfection of a plasmid expressing antisense p27(kip1), which shows that the accumulation of p27(kip1) in these cells is related to their G(1) delay. In summary, we report a new functional link between two important cell cycle regulators, Cdk4 and p27(kip1), and provide a mechanistic explanation to the previously reported epistatic relations between these two proteins.     

Development of the Senegal sole, Solea senegalensis forebrain

The present paper deals with the ontogeny of the forebrain of the flatfish Senegal sole, Solea senegalensis, through different developmental stages before and after to metamorphosis. A first approach was made by conventional histological techniques, which allowed the determination of the main ontogenetic events. A second approach was to analyze the proliferation zones (PZ) during development and their locations, as well as the relation between them and the telencephalic asymmetry of the Senegal sole. The results show that before metamorphosis the Senegal sole goes through a fast development. The pituitary is visible 1 day after hatching (DAH), the inferior lobes of the hypothalamus appear 3 DAH, and the olfactory bulb and the differentiation between telencephalon and diencephalon are present around 4 DAH. In addition, by applying proliferating cell nuclear antigen (PCNA) immunohistochemistry by means of a monoclonal antibody against the PCNA and ABC complex, we were able to determine the PZs in the forebrain of pre- and post- metamorphic specimens. Although in both cases the PZs were similar, in premetamorphic animals they were thicker. However, PZs were observed in the pallium and subpallium, preoptic region, pretectum, epithalamus, dorsal and ventral thalamus, posterior tuberculum and hypothalamus. In all cases the PZs, mainly focusing on the telencephalon, were symmetrical in both hemispheres.     

Localization of structural proteins in African swine fever virus particles by immunoelectron microscopy.

Seven African swine fever virus structural proteins were localized in the virion by immunoelectron microscopy. African swine fever virus-infected cells were incubated, before or after embedding and thin sectioning, with monoclonal antibodies specific for different structural proteins, and after labeling with protein A-gold complexes, the samples were examined in the electron microscope. Proteins p14 and p24 were found in the external region of the virion, proteins p12, p72, p17, and p37 were found in the intermediate layers, and protein p150 was found in the nucleoid and in one vertex. A monoclonal antibody that recognized protein p150 as well as p220, a virus-induced, nonstructural protein, could also bind to a component present in the nucleus of both uninfected and virus-infected cells.     

Inhibition of African swine fever virus binding and infectivity by purified recombinant virus attachment protein p12.

The African swine fever virus protein p12, involved in virus attachment to the host cell, has an apparent molecular mass of 17 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions. We have also identified 12- and 10-kDa forms of the p12 protein in infected Vero cells and found that the mature 17-kDa protein is the only form present in virus particles. The p12 protein has been produced in large amounts in Spodoptera frugiperda insect cells infected with a recombinant baculovirus. A 17-kDa protein that possessed the biological properties of the viral protein was produced, since it bound to susceptible Vero cells and not to receptor-negative L cells, which do not support virus replication. The binding of the baculovirus-expressed protein p12 to Vero cells was specifically blocked by virus particles. In addition, the recombinant protein purified by immunoaffinity chromatography blocked the specific binding of virus particles to susceptible cells and prevented infection, demonstrating that the p12 protein mediates the attachment of virions to specific receptors and indicating that blocking the p12-mediated interaction between African swine fever virus and receptors in Vero cells can inhibit infection. However, although antibodies specific for protein p12 are induced in natural infections and in animals inoculated with inactivated virus or recombinant protein p12, these antisera did not inhibit virus binding to the host cell or neutralize virus infectivity.     

A bacterial artificial chromosome library for soybean and identification of clones near a major cyst nematode resistance gene

 We constructed a bacterial artificial chromosome (BAC) library for soybean (Glycine max) consisting of approximately 30 000 clones with an average insert size of 120 kilobase pairs. The library was successfully screened with restriction fragment length polymorphism (RFLP) and microsatellite markers tightly linked to a major resistance gene for the cyst nematode, Heterodera glycines. Since many soybean RFLPs hybridize to duplicate loci, BACs homologous to duplicate RFLP loci were distinguished by digestion with the restriction enzyme originally used to map the RFLP, followed by a comparison of the hybridizing fragments. Linkage mapping of BAC clones identified with markers linked to the cyst nematode resistance gene demonstrated that these clones were located at the expected chromosomal positions and that there were no indications of chimeras within the genomic inserts. Received: 3 July 1997/Accepted: 26 August 1997