Using weeds to reduce pest insect numbers in organic vegetable crops - a desk study (OF0329)

At present, weeds and pest insects are two of the major constraints to the production of high quality organic vegetable crops, primarily because the range of control measures available to UK growers is extremely limited. Several studies have shown that the numbers of pest insects found on crop plants are reduced considerably when the crops are allowed to become weedy. However, if weeds are not removed by a certain stage of crop growth, they start to compete with the crop plants and yield begins to decline. Warwick HRI already has models that are used independently to predict both the onset of weed competition and the timing of pest insect attacks. However, in practice, growers have to manage weeds and pest insects at the same time and hence the decisions they make often involve compromises. Therefore, it would seem a natural progression to combine the existing models to show how reductions in crop yield, from altered weeding practices, could be offset by improvement in crop quality from reduced pest numbers. The aim of this project was to demonstrate how the existing crop protection models could be used to optimise weed and pest control in organically-grown vegetable crops. The strategy could be very useful, as the range of crop protection interventions available to organic growers is strictly limited. Vegetable brassicas were chosen as the experimental crop, because their pest and weed models have been well validated, and because Brassica crops account for approximately 20% of the total organic vegetables grown in the UK. However, the research also demonstrates how the system could be adapted for other crop/pest combinations. The first objective was to quantify the plant ‘architecture’ needed from weed populations to reduce pest insect infestations in cabbage crops. Three non-host weed plants were used in the study; Chenopodium album (fat hen), Stellaria media (common chickweed) and Tripleurospermum inodorum (scentless mayweed). These species were selected because they are common weeds in field vegetable crops, reduce colonisation by the cabbage root fly (Delia radicum) and have contrasting architecture (spread and height). The treatments combined weed species, planting times, plant sizes and plant densities to examine the impact on pest colonisation of cabbage. The different plant sizes and plant densities were achieved using weed plants that were raised in modules and then planted around cabbage plants. The three test insect species were Brevicoryne brassicae (cabbage aphid), Delia radicum (cabbage root fly) and Plutella xylostella. (diamond-back moth). The trial demonstrated that, for D. radicum and B. brassicae, the greatest reductions in crop colonisation were produced by a high density of large weeds. The effects on P. xylostella were less clear-cut. The second objective was to combine weed and pest insect models to quantify the interactions between crop growth, weed growth and pest insect colonisation. The initial analysis of the data obtained in Objective 1 used a log-linear model to relate pest counts to various assessments of crop (cabbage) and weed plant size (weed fresh weight, weed dry weight, weed height, weed diameter, crop height and number of crop leaves). Whilst these regressions suggested a number of relationships, they often accounted for only a small percentage of the variance. In this second objective, further statistical analyses were done to consider relationships between the numbers of pests per plant and various crop and weed parameters. The ratio of weed biomass to crop biomass (dry weight) provided the strongest relationship with pest numbers, and is also a measurement that can be obtained easily in the field. Using this relationship, critical values were calculated for each pest : weed combination. Maintaining the weed : crop dry weight ratio above this critical value should provide protection against pest colonisation. For example, a weed : crop dry weight ratio of 32.7 was required for S. media to “control” D. radicum. The final objective was to determine the impact of different weeding strategies on 1) yield reduction through weed competition and 2) pest colonisation. A field trial was designed to test these strategies using S. media to ‘control’ D. radicum on cabbage in organic growing conditions. Three ‘weed’ strategies were devised using the crop-weed competition model in combination with the D. radicum forecasting model. They were intended to give: 1) a ratio always greater than the ‘critical value’ (the greatest pest protection, but also the greatest weed competition), 2) a ratio close to the ‘critical value’ (good pest protection, but less crop yield loss than Treatment 1 due to weed competition), and 3) a ratio always below the ‘critical value’ (the least pest protection, but also the least yield loss due to weed competition). Different weed : crop ratios were achieved by transplanting module-raised S. media of different ages into the cabbage plots. The strategies were timed to coincide with periods of either low or high pest incidence in the field, predicted using the D. radicum forecast, and the weeds were removed 4 weeks after transplanting, when the cabbage plants should have been sufficiently wellestablished to withstand a certain amount of root damage. Unfortunately, the growth patterns of some of the weed treatments deviated from predictions made by the crop-weed competition model, so that the ‘strategies’ did not achieve the precise range of weed : crop ratios that had been intended. Despite these deviations, the percentage reduction in cabbage weight at harvest, due to the presence of weeds, was not dissimilar to that predicted by the model. Damage by D. radicum was relatively low. None of the cabbage plants wilted or died, although all suffered larval feeding damage to their roots. However, where the critical ratio was achieved, weed presence had a distinct effect on root damage and the highest density of weeds reduced root damage by the greatest amount when compared with the weed-free control treatment. At harvest, cabbage fresh weight was negatively correlated with the weed : crop ratio, due to competition from the greater biomass of weeds. Thus despite practical difficulties in achieving the intended weed : crop ratios using transplanted weeds, the trial confirmed the value of a ‘green background’ in reducing colonisation by D. radicum. It also confirmed the negative effect of weed competition on crop yield and demonstrated the ‘trade-off’ between reductions in pest damage and yield. Although the weeds were removed after the first 4 weeks of cabbage growth, the high density of weeds required over this period caused a significant reduction in crop yield. Scientific conclusions 1. The current crop-weed competition model is driven purely by radiation interception and this study has highlighted some possible model limitations, in particular, the need to take account of crop and weed growth in nutrient deficient soils and in response to moisture stress. The model also need to be able to cope with multi-species populations of natural weed flora (i.e. parameters need to be obtained for a wider range of species). 2. The crop-weed competition model provides an adequate prediction of competition based on average plant density. Modification of the model to account for the spatial proximity of the plants and their growth plasticity would enable more realistic and practical strategies to be evaluated (e.g. only having weeds within a small radius of the crop plant) 3. Pest models currently provide a robust prediction of the timing of pest infestations, but predictions of pest abundance and subsequent damage would be needed to fully evaluate the trade-off between yield loss through plant competition and the reduction in pest damage. Practical conclusions 1. The trade-off between crop yield and pest control is clearly illustrated by the study. Yield loss (up to 30%) due to competition may be tolerable as an alternative to severe pest damage, in situations where infestation levels are high. Variety choice may have compensatory benefits, however, the impact of varietal choice on competition needs to be explored. 2. The study has shown that the strategy of allowing weed presence for a limited period whilst maintaining a weed : crop ratio (total dry weighs per unit area) above a threshold can provide some protection against pest damage. The threshold is dependent on the pest and weed species involved. 3. In practice, planting into a background of natural flora is probably the most practical way of achieving this protection. However, the weeds would need to be well established before the cabbage was transplanted to achieve the required weed : crop ratio. Further information is needed on the development of natural floras, and on the effect of different weed species compositions. 4. Weeds in close proximity to the crop do reduce pest colonisation, as seen in other studies. Hence a lower total number of weeds could potentially achieve the same protective effect, providing they are close to the crop plant. Further information is needed on the spatial characteristics of plant competition to enable more realistic and practical strategies to be evaluated

Undiagnosed Depression in the Elderly and Healthcare Education

This descriptive study examined undiagnosed depression in the elderly and how it affects the elderly from retaining healthcare education. It is estimated by 2029, 20% of the United States population will be age 65 and older (Colby & Ortman, 2014). Depression in the elderly who have chronic diseases, is estimated to be undiagnosed up to 40% (Chaoyang et al., 2009). A hallmark symptom of depression is the inability to concentrate. It is unknown if undiagnosed depression will affect the older adult from retaining pertinent healthcare education. The 30 point Geriatric Depression Scale (GDS) was administered to a class of elderly individuals, aged 65 years and older. A nutrition class was subsequently taught to the participants. Following the nutrition class, a quiz on the class material was administered to measure retention of the nutritional information. The aim of the study was to determine if higher scores on the GDS, or a positive screening for the risk of depression, would result in lower scores on the nutrition quiz. The scores analyzed as a two tailed Person\u27s correlation, were discovered to be statistically significant at the 0.01 level. The sigma of depression in the setting site contributed to a small sample size. This project has shown the need for increased screening for the risk of depression in the elderly as the elderly cannot retain healthcare education if they are depressed

Ejecta Transfer in the Pluto System

The small satellites of the Pluto system (Styx, Nix, Kerberos, and Hydra) have very low surface escape velocities, and impacts should therefore eject a large amount of material from their surfaces. We show that most of this material then escapes from the Pluto system, though a significant fraction collects on the surfaces of Pluto and Charon. The velocity at which the dust is ejected from the surfaces of the small satellites strongly determines which object it is likely to hit, and where on the surfaces of Pluto and Charon it is most likely to impact. We also show that the presence of an atmosphere around Pluto eliminates most particle size effects and increases the number of dust impacts on Pluto. In total, Pluto and Charon may have accumulated several centimeters of small-satellite dust on their surfaces, which could be observed by the New Horizons spacecraft.Comment: 28 pages, 6 figures, accepted for publication in Icaru

Purinergic receptor mediated calcium signalling in urothelial cells

Non-neuronal ATP released from the urothelium in response to bladder stretch is a key modulator of bladder mechanosensation. Whilst non-neuronal ATP acts on the underlying bladder afferent nerves to facilitate sensation, there is also the potential for ATP to act in an autocrine manner, modulating urothelial cell function. The aim of this study was to systematically characterise the functional response of primary mouse urothelial cells (PMUCs) to ATP. PMUCs isolated from male mice (14-16 weeks) were used for live-cell fluorescent calcium imaging and qRT-PCR to determine the expression profile of P2X and P2Y receptors. The majority of PMUCs (74-92%) responded to ATP (1 μM-1 mM), as indicted by an increase in intracellular calcium (iCa2+). PMUCs exhibited dose-dependent responses to ATP (10 nM-1 mM) in both calcium containing (2 mM, EC50 = 3.49 ± 0.77 μM) or calcium free (0 mM, EC50 = 9.5 ± 1.5 μM) buffers. However, maximum iCa2+ responses to ATP were significantly attenuated upon repetitive applications in calcium containing but not in calcium free buffer. qRT-PCR revealed expression of P2X1-6, and P2Y1-2, P2Y4, P2Y6, P2Y11-14, but not P2X7 in PMUCs. These findings suggest the major component of ATP induced increases in iCa2+ are mediated via the liberation of calcium from intracellular stores, implicating functional P2Y receptors that are ubiquitously expressed on PMUCs.Russell Chess-Williams, Donna J. Sellers, Stuart M. Brierley, David Grundy, Luke Grund

Health inequalities in the older population: the role of personal capital, social resources and socio-economic circumstances.

Older people now constitute the majority of those with health problems in developed countries so an understanding of health variations in later life is increasingly important. In this paper, we use data from three rounds of the Health Survey for England, a large nationally representative sample, to analyse variations in the health of adults aged 65-84 by indicators of attributes acquired in childhood and young adulthood, termed personal capital; and by current social resources and current socio-economic circumstances, while controlling for smoking behaviour and age. We used six indicators of health status in the analysis, four based on self-reports and two based on nurse collected data, which we hypothesised would identify different dimensions of health. Results showed that socio-economic indicators, particularly receipt of income support (a marker of poverty) were most consistently associated with raised odds of poor health outcomes. Associations between marital status and health were in some cases not in the expected direction. This may reflect bias arising from exclusion of the institutional population (although among those under 85 the proportion in institutions is very low) but merits further investigation, especially as the marital status composition of the older population is changing. Analysis of deviance showed that social resources (marital status and social support) had the greatest effect on the indicator of psychological health (GHQ) and also contributed significantly to variation in self-rated health, but among women not to variation in taking three or more medicines and among men not to self-reported long-standing illnesses. Smoking, in contrast, was much more strongly associated with these indicators than with self-rated health. These results are consistent with the view that self-rated health may provide a holistic indicator of health in the sense of well-being, whereas measures such as taking prescribed medications may be more indicative of specific morbidities. The results emphasise again the need to consider both socio-economic and socio-psychological influences on later life health

German crowd-investing platforms: Literature review and survey

This article presents a comprehensive overview of the current German crowd-investing market drawing on a data-set of 31 crowd-investing platforms including the analysis of 265 completed projects. While crowd-investing market still only represents a niche in the German venture capital market, there is potential for an increase in both market volume and in average project investment. The market share is distributed among a few crowd-investing platforms with high entry barriers for new platforms although platforms that specialise in certain sectors have managed to successfully enter the market. German crowd-investing platforms are found to promote mainly internet-based enterprises (36%) followed by projects in real estate (24%) and green projects (19%), with the median money raised 100,000 euro