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

Zero-thickness interface model with chemical degradation by acid attack

Carbon dioxide (CO2) storage in abandoned oil/gas reservoirs is considered a viable alternative to reduce greenhouse gas emissions to the atmosphere. An important element of the risk associated with long-term CO2 storage is the loss of integrity of the cement seals of the abandoned wells in the reservoir. Among others, one possible cause of loss of integrity is the degradation of the oil-well cement due to the acid attack of the carbonated brine in the reservoir. In previous studies, the authors have developed a diffusion-reaction model for simulating this degradation process. In order to study possible coupled Chemo-Mechanical (CM) mechanisms, this model will be coupled with an existing mechanical model. For this purpose, in this paper, an existing constitutive law for zero-thickness interface, based on the theory of elasto-plasticity with concepts of fracture mechanics, is modified to incorporate the effect of chemical degradation on the mechanical strength parameters. Preliminary results obtained with this new constitutive law are presented, in order to illustrate the main aspects of the proposed constitutive law, as well as a possible C-M degradation mechanism that should be considered in the long-term safety assessment of CO2 geological storage projects

Lessons learned: rearing the crown-boring weevil, Ceutorhynchus scrobicollis (Coleoptera: Curculionidae), in containment for biological control of garlic mustard (Alliaria petiolata)

In this paper, we describe lessons learned and protocols developed after a decade of rearing Ceutorhynchus scrobicollis Nerenscheimer and Wagner in a Biosafety Level 2 containment facility. We have developed these protocols in anticipation of approval to release C. scrobicollis in North America for the biocontrol of garlic mustard. The rearing protocol tried to minimize the potential of attack by the adult parasitoid, Perilitus conseutor, which may be present in field collected C. scrobicollis from Europe to prevent inadvertent introduction of parasitoids into North America. All C. scrobicollis used for our quarantine rearing were field collected near Berlin, Germany. We have successfully reared C. scrobicollis on caged garlic mustard plants in a growth chamber by alternating temperatures and photoperiods to simulate those in its native range. In Germany, C. scrobicollis produces one generation per year and F1 adults emerge in late May. In containment, a new generation of adults emerged an average of 108 days after adults were placed on plants. We found the optimal time spent to collect F1 adults was four weeks after the appearance of the first F1 adult, with 95% of potential adults collected. Simulating a three-month summer aestivation period, followed by a week of fall, and three weeks of winter conditions resulted in optimum levels of oviposition in F1 females. Larvae first hatched 8- to-10 days after adults were placed on plants at 15/14 C day/night temperatures with a 9.5 hour photoperiod. We therefore recommend that C. scrobicollis adults are removed from garlic mustard rosettes after 8 days. This will maximize the period of female oviposition while minimizing the time when larvae are available for attack from P. conseutor

Modelling acid attack of oil-well cement exposed to carbonated brine: effect of specimen geometry on experimental results

In recent years, the authors and co-workers have developed a diffusion-reaction model for the degradation process of oil-well cements exposed to carbonated brines in the context of CO2 capture and storage in abandoned oil reservoirs. The model considers two main diffusion-reaction field variables for the concentrations of aqueous calcium and carbon species in the pore solution of the hardened cement paste, complemented by two diffusion-only field variables for chloride and alkalis concentrations. The volume fractions of solid constituents evolve according to the chemical kinetics and chemical equilibrium equations of the reactions involved, determining the diffusivity properties of the material. In this paper, in the framework of an experimental campaign in preparation, this model is used for assessing the effect of different specimen geometries on the kinetics and extent of the acid attack. The results obtained will help to optimize the experimental setup and to the interpretation of the results obtained

Modelling acid attack of oilwell cement exposed to carbonated brine: effect of specimen geometry on experimental results

In recent years, the authors and co-workers have developed a diffusion-reaction model for the degradation process of oilwell cements exposed to carbonated brines in the context of CO2 capture and storage in abandoned oil reservoirs. The model considers two main diffusion/reaction field variables for the concentrations of aqueous calcium and carbon species in the pore solution of the hardened cement paste, complemented by two diffusion-only field variables for chloride and alkalis concentrations. The volume fractions of solid constituents evolve according to the chemical kinetics and chemical equilibrium equations of the reactions involved, determining the diffusivity properties of the material. In this paper, in the framework of an experimental campaign in preparation, this model is used for assessing the effect of different specimen geometries on the kinetics and extent of the acid attack. The results obtained will help to optimize the experimental setup and to the interpretation of the results obtained.Postprint (published version

ChemMatters: Special Issue on NASA's EOS Aura Mission (Sept. 2001)

This EOS-Aura special edition of ChemMatters is the first of four special issues focusing on atmospheric chemistry and the Aura mission. It features articles on global climate change, asthma and air pollution, good and bad ozone, and spectroscopy. ChemMatters is a quarterly publication of the American Chemical Society (ACS) geared to a high school audience. The magazine is designed and written to demystify everyday chemistry. Educational levels: High school