Towards Grower-friendly Apple Crop Thinning by Tree Shading

Light management with shading nets, which reduce sunlight by 74%, might be an alternative to chemicals commonly used for thinning on apple trees. To study the effect of shading on crop load and fruit quality, trials were conducted in field experiments with the cultivars Golden Delicious and Elstar in 2006. Trees were either covered 25 days after full bloom (DAFB) with a net during three days, or until the peak of fruit fall, observed after seven days shading. Ideal time length for optimal crop yield was seven days shading for Elstar and three days shading for Golden Delicious. Alternate bearing could be decreased as flower initiation counts the following year showed. In both experiments, inner quality of fruit such as sugar and firmness showed good values at optimal shading duration compared with chemical + hand thinning. In 2007, a second field trial was conducted with cultivars Golden Delicious and Topaz to study the time period for shading in further detail. Shading was done for three days at 19, 26 and 33 DAFB using two net types (three- and two-meter-net width, covering the trees entirely or only down to 50 cm above ground). For Golden Delicious, shading after 19 and 26 days reduced fruits per 100 flower cluster to the same extent as with chemical + hand thinning. There was no difference between the two net types. For Topaz, shading after 19 days showed the best results. Regarding inner quality of both cultivars, only sugar content for Golden Delicious could be significantly improved after 19 and 26 days shading. Further analyses are still under way (e.g. for acidity). This study is part of an effort for increasing European consumption with fruit from sustainable production systems, the ISAFRUIT-EU-project

Heliothis dispersal and migration

A few of the many species of Heliothis (Lepidoptera, Noctuidae) are important crop pests in the Old and New Worlds. Among these, H.armigera, H.zea, H.virescens and H.punctigera are the best known. The former is a particularly destructive species of a wide range of crops cultivated in Africa, the Middle East and Asia, including several staple foods and important peasant farmer cash crops. As new cultivation techniques are introduced and more extensive areas of crops are grown, often on larger irrigation and Government development schemes, it appears that this pest is becoming increasingly important. There is a strong suspicion that H.armigera populations move locally between crops grown in sequence or intercropped and that probably more extensive migratory movement occurs, as has been demonstrated in the closely related species H. zea in North America. This has considerable implications for effective control of the pest on the crops of some of the least priviledged farmers of the Developing World and in some of the poorest countries. There are recorded instances of resistance to pesticides in the species. Clearly large scale movements could have an effect on dissemination of such resistance and affect the level of control exerted by local parasite and predator populations and hence the necessity for rapid control action to combat rapid population increases of the pest on both staple food and cash crops. The ability to forecast or warn of such incidents would assist in effective timing of control operations and maximise efficiency of any insecticidal input required. This bibliography consolidates much of the scattered literature on the migratory behaviour of Heliothis spp. and will help to identify gaps in the existing knowledge of this aspect of the ecology of the genus. It will hopefully assist in focussing attention on the necessity for work on H.armigera, which is of such great importance in Developing Countries. Work on migratory movement could lead to effective action both regionally and internationally to reduce possibilities of migration of damaging numbers of moths. It will certainly assist in increasing knowledge on the bionomics of one of the most damaging agricultural pest species in the Old World and be of benefit to some of the least advantaged farmers of the tropics

Irreversible reorganization in a supercooled liquid originates from localised soft modes

The transition of a fluid to a rigid glass upon cooling is a common route of transformation from liquid to solid that embodies the most poorly understood features of both phases1,2,3. From the liquid perspective, the puzzle is to understand stress relaxation in the disordered state. From the perspective of solids, the challenge is to extend our description of structure and its mechanical consequences to materials without long range order. Using computer simulations, we show that the localized low frequency normal modes of a configuration in a supercooled liquid are causally correlated to the irreversible structural reorganization of the particles within that configuration. We also demonstrate that the spatial distribution of these soft local modes can persist in spite of significant particle reorganization. The consequence of these two results is that it is now feasible to construct a theory of relaxation length scales in glass-forming liquids without recourse to dynamics and to explicitly relate molecular properties to their collective relaxation.Comment: Published online: 20 July 2008 | doi:10.1038/nphys1025 Available from http://www.nature.com/nphys/journal/v4/n9/abs/nphys1025.htm

Correlation between In Vivo and In Vitro Efficacy of Antimicrobial Agents against Foreign Body Infections

Implant-associated infections are often resistant to antibiotic therapy. Routine sensitivity tests fail to predict therapeutic success. Therefore experimental in vitro tests were sought that would better correlate with drug efficacy in device-related infections. The activity of six different antibiotics against methicillin-resistant Staphylococcus epidermidis was investigated. In vivo studies were performed with the guinea pig tissue-cage animal model; in vitro studies with minimum inhibiting and bactericidal concentrations, time-kill studies of growing and stationary-phase microorganisms, the killing of glass-adherent S. epidermidis. Drug efficacy on stationary and adherent microorganisms, but not minimum inhibiting concentrations, predicted the outcome of device-related infections. Rifampin cured 12 of 12 infections and was also the most efficient drug in any experimental in vitro test. Similarly, the failure of ciproftoxacin to eradicate foreign body infections correlated with its low efficacy on stationary-phase and adherent S. epidermidi

Are there localized saddles behind the heterogeneous dynamics of supercooled liquids?

We numerically study the interplay between heterogeneous dynamics and properties of negatively curved regions of the potential energy surface in a model glassy system. We find that the unstable modes of saddles and quasi-saddles undergo a localization transition close to the Mode-Coupling critical temperature. We also find evidence of a positive spatial correlation between clusters of particles having large displacements in the unstable modes and dynamical heterogeneities.Comment: 7 pages, 3 figures, submitted to Europhys. Let