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IntroductionFall armyworm continues to disrupt smallholder farming systems across sub-Saharan Africa, with sporadic outbreaks and chronic cereal crop losses. Smallholders have been adapting to the pest by increasing crop surveillance for targeted control measures and developing low-cost solutions. For example, some report placing soil or ash in maize whorls where the mechanism of pest control may be suffocation, abrasion leading to desiccation, or through the introduction of soil-borne entomopathogens.MethodsTo verify the efficacy of this approach we evaluated different soil types on maize infested with fall armyworm to assess their efficacy. We also evaluated the efficacy of pesticidal plant species, powdered and placed in leaf whorls to control fall armyworm. Results and discussionDifferent United States Department of Agriculture-characterised soil types (sand, loam, clay) and wood ash were effective in reducing the number of larvae and maize leaf damage by approximately 50%. Maize yield with the synthetic control (chlorpyriphos) was 13,700 kg/ha, which was 42% higher than the untreated control (7,900 kg/ha). Soil and ash treatments yields between 10,400 to 12,400 kg/ha were 24-36% higher than the untreated control. Dry soil applied after watering was most effective regardless of soil type. However, wet soil treatments applied before watering were also highly effective in reducing the number of fall armyworm larvae and reducing insect damage to maize leaves. Botanical powders from Azadirachta indica, Nicotiana tabacum, Cymbopogon citratus and Lippia javanica were also effective when applied to maize leaf whorls. Plant powder treatments and water extracts were significantly effective in reducing the number of larvae and leaf damage. The highest yield obtained with botanicals was observed with A. indica powder (5,600 kg/ha), C. citratus extract (5,800 kg/ha) and N. tabacum extract (5,800 kg/ha), where the synthetic treatment yield was 6,900 kg/ha and the untreated yield was 1,700 kg/ha. We conclude that smallholder farmer innovations in managing fall armyworm are effective low-cost options. Scientific validation of soil treatments and botanicals should help increase the confidence of policy makers and allow knowledge extension services to recommend their use to smallholder farmers, which in turn may reduce reliance on imported synthetic pesticides and improve farmer resilience, circular economies and human and environmental health.

The azimuthal dynamics of ions along the inner pole of a Hall thruster with a centrally mounted cathode and a magnetic shielding topography are experimentally investigated. A time-averaged laser-induced fluorescence diagnostic is implemented to characterize the azimuthal ion velocity distribution, and its moments are computed numerically to infer bulk rotation speed and ion temperature. It is found that the time-averaged ion swirl velocity grows to 2 km/s in the near-pole region, and the cathode ions exhibit ion temperatures in the azimuthal direction approaching 8 eV. Both of these quantities exceed the speeds and temperatures anticipated from classical acceleration and heating. Time-resolved laser-induced fluorescence is then employed to investigate the role of plasma fluctuations in driving the time-averaged ion properties. Semicoherent fluctuations at 90 kHz are observed in the ion velocity distribution and its associated moments. These oscillations are correlated with the gradient-driven anti-drift wave, which propagates azimuthally in the near-field cathode plume. Quasilinear theory is used to construct a 1D model for acceleration and heating of the ion population as a result of the anti-drift mode. This approach demonstrates qualitative agreement with the time-averaged ion velocity and temperature, suggesting that the anti-drift mode may be a dominant driver of azimuthal ion acceleration and heating in front of the cathode keeper and the inner half of the inner front pole cover. These results are discussed in terms of their relevance to the erosion of thruster surfaces in the near-field cathode plume. [ABSTRACT FROM AUTHOR]

A first-principles model of the anomalous momentum-transfer collision frequency for electrons ( v e a ) in E × B ion accelerators, also known as Hall-effect thrusters, is presented. The theory on which the model is based adopts a two-stage evolution of unstable waves. First, short-wavelength ( k ⊥ ρ e > 1), high-frequency ( ω ∼ ω c e ) modes that are driven by the cross-field drift υ E = E × B / B 2 grow and saturate at a level of turbulence too low to explain the observed measurements. Then, the wave energy is dominated by modes of longer wavelength ( k ⊥ ρ e < 1) and in the range of the lower-hybrid frequency ω L H = ω p i / 1 + ω p e 2 / ω c e 2 ½ . The lower-hybrid modes combine wave growth in the azimuthal direction that is driven by the diamagnetic drift υ D e = ∇ p e × B / e n B 2 , with growth parallel to B due to a higher effective mass of electrons. The latter has been typically identified as the modified two-stream instability. The diamagnetic-driven modes are found to be important in regions of the channel where ions begin to accelerate since υ E ∼ υ D e there. The theoretical model compares extremely well with a large set of empirical profiles of v e a derived from laser-induced fluorescence measurements. Our model validation comparisons spanned thrusters with >10× range in discharge power, various sizes and operating conditions, in unshielded and shielded magnetic field topologies. The kinetic version of our closed-form expression yields the scaling v e a ∼ ω c e υ T i e τ ¯ / (υ E + υ D e) , where τ ¯ ∼ ω L H / v i , v i is the sum of the ionization and charge-exchange frequencies and υ T i is the ion thermal speed. The latter must be determined by the appropriate integration of the ion velocity distribution function and include not only random changes of the drift velocity but also ion production. [ABSTRACT FROM AUTHOR]

Against a background of continuing loss of biodiversity, it is argued that for the successful conservation of threatened plant species we need to ensure the more effective integration of the various conservation actions employed, clarify the wording of the CBD targets and provide clearer operational guidance as to how they are to be implemented and their implementation monitored. The role and effectiveness of protected areas in conserving biodiversity and in particular plant species in situ are discussed as are recent proposals for a massive increase of their extent. The need for much greater effort and investment in the conservation or protection of threatened species outside protected areas where most plant diversity occurs is highlighted. The difficulties involved in implementing effective in situ conservation of plant diversity both at an area- and species/population-based level are discussed. The widespread neglect of species recovery for plants is noted and the desirability of making a clearer distinction between species recovery and reintroduction is emphasized. Key messages from a global overview of species recovery are outlined and recommendations made, including the desirability of each country preparing a national species recovery strategy. The projected impacts of global change on protected areas and on species conservation and recovery, and ways of addressing them are discussed. Keywords: Plant conservation, CBD targets, Protected areas, Species recovery, Conservation approaches

Plasma oscillations below 100 kHz in a high-power, magnetically shielded Hall-effect thruster are characterized experimentally. A time-resolved laser-induced fluorescence diagnostic was used to measure the evolution of the axial ion velocity distribution along the discharge channel centerline. A method was developed to correct for artificial broadening of the distribution due to finite spatial resolution, enabling accurate ion temperature measurements in the acceleration region. Time-dependent ion heating behavior is revealed, which varies with axial location. Electrostatic, collisionless particle-pushing calculations were employed to simulate the effects of a shifting acceleration front on ion motion. It is found that ions exchange energy with these oscillations, which accounts for a portion of the ion velocity fluctuations observed in the thruster plume. Phasing relationships between ion dynamics and discharge current oscillations are discussed in the context of prior Hall thruster experiments. [ABSTRACT FROM AUTHOR]

As an introduction to the Special Issue on the restoration of threatened plant species and their habitats, this editorial shows how the various papers in the issue address the range of in situ interventions involved in species population management and restoration of their habitat, together with examples of case studies implementing these actions. It stresses the need for integrating these various interventions. It highlights the importance of protected areas in providing a degree of protection for threatened species but also the need to complement this with actions at the species level to ensure the effective conservation and long term persistence of these species. It emphasizes that ecological restoration is a complement to, not a substitute for conservation, and that the balance of effort and allocation of resources between them is a key issue. Keywords: Threatened species management, Habitat restoration, In situ conservation, Protected areas

Despite the massive efforts that have been made to conserve plant diversity across the world during the past few decades, it is becoming increasingly evident that our current strategies are not sufficiently effective to prevent the continuing decline in biodiversity. As a recent report by the CBD indicates, current progress and commitments are insufficient to achieve the Aichi Biodiversity Targets by 2020. Threatened species lists continue to grow while the world's governments fail to meet biodiversity conservation goals. Clearly, we are failing in our attempts to conserve biodiversity on a sufficient scale. The reasons for this situation are complex, including scientific, technical, sociological, economic and political factors. The conservation community is divided about how to respond. Some believe that saving all existing biodiversity is still an achievable goal. On the other hand, there are those who believe that we need to accept that biodiversity will inevitably continue to be lost, despite all our conservation actions and that we must focus on what to save, why and where. It has also been suggested that we need a new approach to conservation in the face of the challenges posed by the Anthropocene biosphere which we now inhabit. Whatever view one holds on the above issues, it is clear that we need to review the effectiveness of our current conservation strategies, identify the limiting factors that are preventing the Aichi goals being met and at the same time take whatever steps are necessary to make our conservation protocols more explicit, operational and efficient so as to achieve the maximum conservation effect. This paper addresses the key issues that underlie our failure to meet agreed targets and discusses the necessary changes to our conservation approaches. While we can justifiably be proud of our many achievements and successes in plant conservation in the past 30 years, which have helped slow the rate of loss, unless we devise a more coherent, consistent and integrated global strategy in which both the effectiveness and limitations of our current policies, action plans and procedures are recognized, and reflect this in national strategies, and then embark on a much bolder and ambitious set of actions, progress will be limited and plant diversity will continue to decline. Keywords: Plant conservation, Anthropocene, Aichi targets, Biodiversity governance, Protected areas

We revisit the estimation of the power deposited by the electron cloud (EC) in the arc dipoles of the LHC by means of simulations. We adopt, as simulation input, a set of electron-related parameters closely resembling those used in recent simulations at CERN [1]. We explore values for the bunch population Nb in the range 0.4 x 10^11 2 and Nb > 1.5 x 10^11 taken in combination. The rediffused component of the secondary electron emission spectrum plays a significant role: if we artificially suppress this component while keeping delta max fixed, dPbar/dz is roughly cut in half for most values of Nb explored here, and in this case we find good agreement with the results in Ref. 1, as expected. We provide a fairly detailed explanation of the mechanism responsible for such a relatively large effect. We assess the sensitivity of our results to numerical simulation parameters, and to physical parameters such as the photoelectric yield, bunch train length, etc. Owing to the lack of detailed knowledge of the electron emission spectrum, the sensitivity of dPbar/dz to the rediffused component appears to be the most significant source of uncertainty in our results. Nevertheless, taking our results as a whole, the condition delta max