An Overview of the Vine Mealybug (Planococcus ficus) in South African Vineyards and the Use of Entomopathogenic Nematodes as Potential Biocontrol Agent

The vine mealybug, Planococcus ficus (Hemiptera: Pseudococcidae), which is the dominant mealybugspecies in South Africa, is a severe wine and table grape pest and disease vector. Their increasingresistance to chemical pesticides and cryptic lifestyles have led to the search for new control methods.Entomopathogenic nematodes (EPNs) belonging to the families Heterorhabditidae and Steinernematidaeare deadly insect pathogens. This paper gives valuable background information on P. ficus and EPNs,while paying particular attention to the potential use of South African EPN species as biocontrol agentsagainst P. ficus

The Potential Use of Entomopathogenic Nematodes to Control Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Laboratory bioassays were conducted to establish the potential of entomopathogenic nematodes (EPNs) asbiocontrol agents of Planococcus ficus (Signoret). Six indigenous and two commercially available nematodespecies were screened for their efficacy in killing adult female P. ficus. The two indigenous species withthe most promising results were Heterorhabditis zealandica and Steinernema yirgalemense, which wereresponsible for 96% and 65% mortality respectively. Tests were conducted to compare the efficacy ofH. bacteriophora and S. feltiae produced in vivo and in vitro. Heterorhabditis bacteriophora showed nosignificant difference in efficacy between the two production methods, but in vivo-cultured S. feltiaeproduced a significantly higher mean mortality of 40%, in contrast to a 19% mean mortality with in vitroproducedinfective juveniles (IJs). The capability of both H. zealandica and S. yirgalemense to completetheir life cycles in the host and to produce a new cohort of IJs was demonstrated. Bioassays indicateda concentration-dependent susceptibility of P. ficus to H. zealandica, S. yirgalemense and commerciallyproduced H. bacteriophora, with LC50 and LC90 values of 19, 82; 13, 80; and 36, 555 respectively. Both H.zealandica and S. yirgalemense were able to move 15 cm vertically downward and infect P. ficus with arespective mortality of 82% and 95%. This study showed P. ficus to be a suitable host for H. zealandicaand S. yirgalemense, with both nematode species showing considerable potential for future use in the fieldcontrol of P. ficus

The Potential Use of Entomopathogenic Nematodes to Control Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Laboratory bioassays were conducted to establish the potential of entomopathogenic nematodes (EPNs) asbiocontrol agents of Planococcus ficus (Signoret). Six indigenous and two commercially available nematodespecies were screened for their efficacy in killing adult female P. ficus. The two indigenous species withthe most promising results were Heterorhabditis zealandica and Steinernema yirgalemense, which wereresponsible for 96% and 65% mortality respectively. Tests were conducted to compare the efficacy ofH. bacteriophora and S. feltiae produced in vivo and in vitro. Heterorhabditis bacteriophora showed nosignificant difference in efficacy between the two production methods, but in vivo-cultured S. feltiaeproduced a significantly higher mean mortality of 40%, in contrast to a 19% mean mortality with in vitroproducedinfective juveniles (IJs). The capability of both H. zealandica and S. yirgalemense to completetheir life cycles in the host and to produce a new cohort of IJs was demonstrated. Bioassays indicateda concentration-dependent susceptibility of P. ficus to H. zealandica, S. yirgalemense and commerciallyproduced H. bacteriophora, with LC50 and LC90 values of 19, 82; 13, 80; and 36, 555 respectively. Both H.zealandica and S. yirgalemense were able to move 15 cm vertically downward and infect P. ficus with arespective mortality of 82% and 95%. This study showed P. ficus to be a suitable host for H. zealandicaand S. yirgalemense, with both nematode species showing considerable potential for future use in the fieldcontrol of P. ficus

Prospects for Using Entomopathogenic Nematodes to Control the Vine Mealybug, Planococcus ficus, in South African Vineyards

In South Africa, the most common method of mealybug control has been the use of chemical insecticides.Entomopathogenic nematodes (EPNs) of the of the families Heterorhabditidae and Steinernematidaepotentially can be used within an integrated pest management scheme to control Planococcus ficus, the vinemealybug, which occurs on all parts of grapevine, including the roots. When Steinernema yirgalemensewas applied to the soil of two vineyards with P. ficus, contained in pierced Eppendorf tubes, buried ata depth of 15 cm in the soil, mortalities of up to 50% were obtained after 48 h. The persistence of S.yirgalemense, measured using codling moth larval mortality was found to be zero in one vineyard, whilein the other it was 70%, 12 weeks after application. Tests were conducted to establish the production ofscavenger deterrent factors by H. zealandica and S. yirgalemense. Of the cadavers that were presentedsix days after nematode infection, 49% of the H. zealandica- and 60% of the S. yirgalemense-infectedcadavers were left intact. Olfactometry tests indicated a significant difference concerning the number ofS. yirgalemense infective juveniles (IJs) that were attracted to damaged Vitis vinifera roots and P. ficus,indicating active movement of the IJs and the attractive ability of organic compounds produced by theroots. This study shows that EPNs, and specifically S. yirgalemense, have promising potential as biologicalcontrol agents for the control of P. ficus soil populations, and investigates some influential factors affectingEPNs as biocontrol agents in the agro-ecosystem

Retention of radiotranslucent foreign bodies in the oesophagus as a cause of stridor

Two infants who presented with stridor were found to have radiotranslucent plastic objects impacted in the oesophagus at the level of the cricoid cartilage. From these 2 cases the lessons to be learnt are that oesophageal foreign bodies retained for even a short period may be a cause of stridor and that when these foreign bodies are not radiographically visible investigation must include the swallowing of contrast medium in which the foreign body should be visible as a translucency.S. Afr. Med. J., 48, 831 (1974)

Factors controlling gully development : comparing continuous and discontinuous gullies

Gully erosion is a degradation process affecting soils in many parts of theWorld. Despite the complexity of a series of collective factors across different spatial scales, previous research has not yet explicitly quantified factor dominance between different sized gullies. This factorial analysis quantifies the differences in factor dominance between continuous gullies (cgs) and discontinuous gullies (dgs). First, gullies (totaling 5273 ha) visible from SPOT 5 imagery were mapped for a catchment (nearly 5000 km2) located in the Eastern Cape Province of South Africa. Eleven important factors were integrated into a geographical information system including topographical variables, parent material-soil associations and land use–cover interactions. These were utilized in a zonal approach in order to determine the extent factors differ between cgs and dgs. Factors leading to the development of cgs are gentle footslopes in zones of saturation along drainage paths with a large contributing area, erodible duplex soils derived from mudstones and poor vegetation cover due to overgrazing. Compared to cgs conditions, more dgs occur on rolling slopes where the surface becomes less frequently saturated with a smaller contributing area, soils are more stable and shallow. Factorial analysis further illustrates that differences in factor dominance between the two groups of gullies is most apparent for soil factors. A combination of overgrazing and susceptible mudstones proves to be key factors that consistently determine the development of cgs and dgs.The ARC-ISCW, as well as Mr. D. J. Pretorius and his colleagues at the Department of Agriculture Forestry and Fisheries (DAFF), Directorate Land Use and Soil Management.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145X

Water erosion risk assessment in South Africa : a proposed methodological framework

With the increase in human impacts on the environment, especially in terms of agricultural intensification and climate change, erosion processes need to be assessed and continually monitored. In many countries, but particularly in developing countries such as South Africa, standardized methodological frameworks that deliver comparable results across large areas as a baseline for regional scale monitoring are absent. Due to limitations of scale at which techniques can be applied and erosion processes assessed, this study describes a multi-process and multiscale approach for soil erosion risk assessment under South African conditions. The framework includes assessment of sheet-rill erosion at a national scale based on the principles and components defined in the Universal Soil Loss Equation; gully erosion in a large catchment located in the Eastern Cape Province by integrating 11 important factors into a GIS; and sediment migration for a research catchment near Wartburg in KwaZulu-Natal by means of the Soil andWater Assessment Tool. Three hierarchical levels are presented in the framework, illustrating the most feasible erosion assessment techniques and input datasets that are required for application at a regional scale with proper incorporation of the most important erosion contributing factors. The methodological framework is not interpreted as a single assessment technique but rather as an approach that guides the selection of appropriate techniques and datasets according to scale dependency and modelled complexity of the erosion processes.National Research Foundationhttp://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1468-0459hb201

Modeled Insulin Sensitivity and Interstitial Insulin Action from a Pilot Study of Dynamic Insulin Sensitivity Tests

An accurate test for insulin resistance can delay or prevent the development of Type 2 diabetes and its complications. The current gold standard test, CLAMP, is too labor intensive to be used in general practice. A recently developed dynamic insulin sensitivity test, DIST, uses a glucose-insulin-C-peptide model to calculate model-based insulin sensitivity, SI. Preliminary results show good correlation to CLAMP. However both CLAMP and DIST ignore saturation in insulin-mediated glucose removal. This study uses the data from 17 patients who underwent multiple DISTs to investigate interstitial insulin action and its influence on modeled insulin sensitivity. The critical parameters influencing interstitial insulin action are saturation in insulin receptor binding, αG, and plasma-interstitial difiusion rate, nI . Very low values of αG and very low values of nI produced the most intra-patient variability in SI. Repeatability in SI is enhanced with modeled insulin receptor saturation. Future parameter study on subjects with varying degree of insulin resistance may provide a better understanding of different contributing factors of insulin resistance

Measurement of the binding energy of ultracold 87Rb133Cs molecules using an offset-free optical frequency comb

We report the binding energy of Rb87Cs133 molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly bound Feshbach state to the rovibrational ground state with a resolution of ∼5 kHz over an energy-level difference of more than 114THz; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach-state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of h×114268135.24(4)(3)MHz. To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule

Enhancement of the Two-channel Kondo Effect in Single-Electron boxes

The charging of a quantum box, coupled to a lead by tunneling through a single resonant level, is studied near the degeneracy points of the Coulomb blockade. Combining Wilson's numerical renormalization-group method with perturbative scaling approaches, the corresponding low-energy Hamiltonian is solved for arbitrary temperatures, gate voltages, tunneling rates, and energies of the impurity level. Similar to the case of a weak tunnel barrier, the shape of the charge step is governed at low temperatures by the non-Fermi-liquid fixed point of the two-channel Kondo effect. However, the associated Kondo temperature TK is strongly modified. Most notably, TK is proportional to the width of the level if the transmission through the impurity is close to unity at the Fermi energy, and is no longer exponentially small in one over the tunneling matrix element. Focusing on a particle-hole symmetric level, the two-channel Kondo effect is found to be robust against the inclusion of an on-site repulsion on the level. For a large on-site repulsion and a large asymmetry in the tunneling rates to box and to the lead, there is a sequence of Kondo effects: first the local magnetic moment that forms on the level undergoes single-channel screening, followed by two-channel overscreening of the charge fluctuations inside the box.Comment: 21 pages, 19 figure