Combining lacewings and parasitoids for biological control of foxglove aphids in sweet pepper

The role of natural enemy diversity in biological pest control has been debated in many studies, and understanding how interactions amongst predators and parasitoids affect herbivore populations is crucial for pest management. In this study, we assessed the individual and combined use of two species of natural enemies, the parasitoid Aphidius ervi Haliday, and the predatory brown lacewing Micromus variegatus (Fabricius), on their shared prey, the foxglove aphid, Aulacorthum solani (Kaltenbach), on sweet pepper. We hypothesized that the presence of intraguild predation (IGP) and predator facilitation (through induced aphid dropping behaviour) might have both negative and positive effects on aphid control, respectively. Our greenhouse trial showed that overall, the greatest suppression of aphids occurred in the treatment with both the parasitoid and the lacewing. While the combination of lacewings and parasitoids significantly increased aphid control compared to the use of parasitoids alone, the effect was not significantly different to the treatment with only predators, although there was a clear trend of enhanced suppression. Thus, the combined effects of both species of natural enemies were between additive and non-additive, suggesting that the combination is neither positive nor negative for aphid control. High levels of IGP, as proven in the laboratory, were probably compensated for by the strong aphid suppression provided by the lacewings, whether or not supplemented with some level of predator facilitation. For aphid management over a longer time scale, it might still be useful to combine lacewings and parasitoids to ensure stable and resilient aphid control.Fil: Rocca, Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Messelink, Gerben J.. University of Agriculture Wageningen; Países Bajo

The Continuum Slopes of Optically Selected QSOs

Quasi-simultaneous optical/near-IR photometry is presented for a sample of 37 luminous optically selected QSOs drawn from the Large Bright QSO Survey. Most of the QSOs have decreased in brightness since discovery; this is expected in flux-limited samples. The continuum shape of most of the QSOs can be represented by a power-law of the form F(nu) = nu**-0.3, but a few have softer (redder) continuum slopes.Comment: 14 pages, LaTeX, 2 postscript figures. Accepted for publication in Publ. AS

Bench-to-bedside review: The importance of the precision of the reference technique in method comparison studies - with specific reference to the measurement of cardiac output

Bland-Altman analysis is used for assessing agreement between two measurements of the same clinical variable. In the field of cardiac output monitoring, its results, in terms of bias and limits of agreement, are often difficult to interpret, leading clinicians to use a cutoff of 30% in the percentage error in order to decide whether a new technique may be considered a good alternative. This percentage error of ± 30% arises from the assumption that the commonly used reference technique, intermittent thermodilution, has a precision of ± 20% or less. The combination of two precisions of ± 20% equates to a total error of ± 28.3%, which is commonly rounded up to ± 30%. Thus, finding a percentage error of less than ± 30% should equate to the new tested technique having an error similar to the reference, which therefore should be acceptable. In a worked example in this paper, we discuss the limitations of this approach, in particular in regard to the situation in which the reference technique may be either more or less precise than would normally be expected. This can lead to inappropriate conclusions being drawn from data acquired in validation studies of new monitoring technologies. We conclude that it is not acceptable to present comparison studies quoting percentage error as an acceptability criteria without reporting the precision of the reference technique

Gamma Ray Burst Host Galaxies Have `Normal' Luminosities

The galactic environment of Gamma Ray Bursts can provide good evidence about the nature of the progenitor system, with two old arguments implying that the burst host galaxies are significantly subluminous. New data and new analysis have now reversed this picture: (A) Even though the first two known host galaxies are indeed greatly subluminous, the next eight hosts have absolute magnitudes typical for a population of field galaxies. A detailed analysis of the 16 known hosts (ten with red shifts) shows them to be consistent with a Schechter luminosity function with $R^{*} = -21.8 \pm 1.0$ as expected for normal galaxies. (B) Bright bursts from the Interplanetary Network are typically 18 times brighter than the faint bursts with red shifts, however the bright bursts do not have galaxies inside their error boxes to limits deeper than expected based on the luminosities for the two samples being identical. A new solution to this dilemma is that a broad burst luminosity function along with a burst number density varying as the star formation rate will require the average luminosity of the bright sample ($>$$6 \times 10^{58} ph \cdot s^{-1}$ or $>$$1.7 \times 10^{52} \cdot erg \cdot s^{-1}$) to be much greater than the average luminosity of the faint sample ($\sim 10^{58} ph \cdot s^{-1}$ or $\sim 3 \times 10^{51} erg \cdot s^{-1}$). This places the bright bursts at distances for which host galaxies with a normal luminosity will not violate the observed limits. In conclusion, all current evidence points to GRB host galaxies being normal in luminosity.Comment: 18 pages, 3 figures, Submitted to ApJLet

Cw recombination laser in a flowing negative glow plasma

Includes bibliographical references (page 1147).cw laser oscillation has been obtained in the 1.43-μm line of Cd I populated by electron-ion recombination in the flowing afterglow of a negative glow plasma. The metal vapor in there combining plasma is produced at room temperature by cathode sputtering. Negative glow plasmas having an electron energy distribution in which energetic beam electrons and supercooled secondary electrons coexist under steady-state conditions are shown to be an attractive medium for the excitation of cw recombination lasers