Potential and Limits of Pesticide Free Apple Growing by a Self-Regulating Orchard Set-Up: Project Presentation and First Experiences

Different research groups have already proven that flowering plants in orchards can enhance beneficial arthropods. Even within the tree rows different beneficial can be supported by selected plant species. In most experimental work done to stabilize the apple production system only single interaction effects were tested. However until now, no research group has quantified the additive effects of multiple measures on systembiodiversity and on the production economy. Our experiment combines all known measures of indirect pest and disease control measures in a near-to practical production model orchard without the use of any pesticide (not even organic ones). The orchard is split in 4 blocks: in two of them bio-control measures e.g. application of Granulosis Virus against codling moth (C. Pomonella) are applied; in the other two blocks no bio-control is applied. Standard commercial organic and integrated orchards with the disease-susceptible cultivar Gala in the vicinity of the model orchard are assessed by the same methods and serve as reference. Our intermediate results reveal that the self-regulating orchard developed already in the 2nd and 3rd leaf a clearly higher flora and fauna biodiversity compared to the reference orchards. The same happened in relation to the specific fruit beneficial e.g. the populations of aphid predators. In the self-regulating orchard they were capable to keep the aphid damages – in particular of the powdery apple aphid (D. plantaginea) - on trees and fruits under a commercially relevant level although the initial abundance of aphid colonies in spring was by far over the common threshold value. It is planned to continue the experiment until 2016

Design and characterization of optical-THz phase-matched traveling-wave photomixers

Design and characterization of optical-THz phase-matched traveling-wave photomixers for difference-frequency generation of THz waves are presented. A de-biased coplanar stripline fabricated on low-temperature-grown GaAs is illuminated by two non-collinear laser beams which generate moving interference fringes that are accompanied by THz waves. By tuning the offset angle between the two laser beams, the velocity of the interference fringe can be matched to the phase velocity of the THz wave in the coplanar stripline. The generated THz waves are radiated into free space by the antenna at the termination of the stripline. Enhancement of the output power was clearly observed when the phase-matching condition was satisfied. The output power spectrum has a 3-dB bandwidth of 2 THz and rolls off as ~9 dB/Oct which is determined by the frequency dependent attenuation in the stripline, while the bandwidth of conventional photomixer design has the limitation by the RC time constant due to the electrode capacitance. The device can handle the laser power of over 380 mW, which is 5 times higher than the maximum power handring capability of conventional small area devices. The results show that the traveling-wave photomixers have the potential to surpass small area designs, especially at higher frequencies over I THz, owing to their great thermal dissipation capability and capacitance-free wide bandwidth

Traveling-Wave Photomixers Based On Noncollinear Optical/Terahertz Phase-Matching

Traveling-wave THz photomixers based on angle-tuned optical/THz phase-matching are experimentally demonstrated. A dc-biased coplanar stripline terminated by a planar antenna is fabricated on low-temperature-grown GaAs. A distributed area between the striplines is illuminated by two noncollinear laser beams which generate interference fringes accompanied by THz waves. The velocity of the optical fringe is matched to the THz-wave velocity in the stripline by tuning the incident angle of the laser beams. The device can handle the laser power over 300 mW and provides the THz output of ~0.1 µW with the 3-dB bandwidth of 2 THz. The experimental results show that traveling-wave photomixers have the potential to surpass conventional small area designs

A traveling-wave THz photomixer based on angle-tuned phase matching

A traveling-wave THz photomixer based on a free-space optical-THz phase-matching scheme is proposed. A dc-biased coplanar strip line fabricated on low-temperature-grown GaAs serves as the active area of the device, and is illuminated by two noncollinear laser beams which generate interference fringes that are accompanied by THz waves. The device with the laser-power-handling capability over 300 mW and a 3-dB bandwidth of 1.8 THz was experimentally demonstrated. The results show that traveling-wave photomixers have the potential to surpass small-area designs

Competition of different coupling schemes in atomic nuclei

Shell model calculations reveal that the ground and low-lying yrast states of the $N=Z$ nuclei $^{92}_{46}$Pd and $^{96}$Cd are mainly built upon isoscalar spin-aligned neutron-proton pairs each carrying the maximum angular momentum J=9 allowed by the shell $0g_{9/2}$ which is dominant in this nuclear region. This mode of excitation is unique in nuclei and indicates that the spin-aligned pair has to be considered as an essential building block in nuclear structure calculations. In this contribution we will discuss this neutron-proton pair coupling scheme in detail. In particular, we will explore the competition between the normal monopole pair coupling and the spin-aligned coupling schemes. Such a coupling may be useful in elucidating the structure properties of $N=Z$ and neighboring nuclei.Comment: 10 pages, 7 figures, 1 table. Proceedings of the Conference on Advanced Many-Body and Statistical Methods in Mesoscopic Systems, Constanta, Romania, June 27th - July 2nd 2011. To appear in Journal of Physics: Conference Serie

Do wildflower strips enhance pest control in organic cabbage?

Within this project we assess whether wildflower strips and companion plants increase the control of cabbage pests Plutella xylostella L. (Lepidoptera: Plutellidae), Mamestra brassicae L. (Lepidoptera: Noctuidae) and Pieris rapae L. (Lepidoptera: Pieridae) by (1) naturally occurring parasitoids and predators and (2) mass‐releasedn Trichogramma brassciae (Bezdenko) (Hymenoptera: Trichogrammatidae) parasitoids. Two organic cabbage fields were used for this study: adjacent to each field a wildflower strip was sown and companion plants (Centaurea cyanus L. (Asteraceae)) intermixed within the crop. Within each field ~15,000 M. brassicae eggs were placed out to determine the parasitism rates by mass‐released T. brassicae and to assess the levels of egg predation. Over 1,000 lepidopteran larvae were collected and screened for hymenopteran and tachinid parasitoid DNA using a multiplex PCR assay. Invertebrate generalist predators (n=1,063) were collected for DNA‐based gut content analysis. The wildflower strip had a significant positive effect on M. brassicae egg parasitism rates as rates increased 5‐fold in the vicinity to the strip. Moreover, companion plants enhanced invertebrate predation on M. brassicae eggs. Both, the release of T. brassicae and the use of companion plants, however, did not significantly increase egg parasitism rates. The infestation of plants by caterpillars increased with distance to the wildflower strip and there was a trend of decreasing larval parasitism rates with distance to the strip. Currently the invertebrate predators are being molecularly analysed to assess predation on unparasitized and parasitized lepidopteran pests