Search

Feral boar have relatively recently become established in woodlands in Great Britain, but the long-term effect of their presence, in particular rooting activity, on woodland habitats and biodiversity is unknown. Protocols to investigate boar presence, densities and impacts to inform policy makers and practitioners are being investigated within a collaborative project by Forest Research and The Food and Environment Research Agency, funded by Forestry Commission and Defra. Results are presented from initial studies on plants and invertebrates carried out in a series of woodlands in south east England.

A field trial conducted in the summer of 2011 evaluated three key parameters that might be influential for determining the number of adult male oak processionary moths ( OPM) Thaumetopoea processionea (L.) caught in pheromone traps. Two types of traps (Delta and funnel; Oecos, U.K.) containing one of three different commercially available pheromone lures for OPM were placed out in the lower (3-5 m), mid (5-10 m) and upper (10-15 m) canopy of 72 individual oak trees in Richmond Park, in London, U.K., The traps were placed out for 8 weeks covering the main flight period of OPM, and significantly more male moths were captured in traps positioned in the upper canopy (76.6%) compared with either mid-canopy (18.6%) or lower canopy (4.8%) positions. Funnel traps caught significantly more male OPM than Delta traps, catching almost six times as many moths over the trapping period., Traps containing one of the commercially available pheromone lures did not catch any moths, whereas traps with the other two lures caught similar numbers of moths. Chemical analysis revealed considerable differences between the three pheromone lures used in the trial in terms of the initial starting concentration of the primary component ( Z, Z)-11,13-hexadecadienyl acetate and its dissipation over a 28-day period., The results obtained in the present study indicate some of the main factors that need to be taken into account when using pheromone traps to monitor OPM populations and also contribute to the establishment of a standardized monitoring system for this recently established insect pest. [ABSTRACT FROM AUTHOR]

Adults of the leaf weevil Phyllobius pyri (L.) (Coleoptera: Curculionidae) feed on a wide variety of broadleaved trees and occasionally cause severe defoliation in newly established farm woodlands. There is little information, however, on the relative susceptibility of different tree species to damage or on the habitat associations of adults and larvae of P. pyri, which might indicate the conditions that predispose trees to attack. Captures of adult P. pyri in emergence and flight traps in the current study indicated population densities in grassland of 0.5-6.4 adults per m2 at emergence but higher densities up to 13.5 per m2 in young pine plantations, where there was a mixture of grassy patches and young, naturally regenerating birch trees. The close proximity of larval food resources (grass roots) and a favoured adult host-plant, which also occurs in young farm woodlands, provided ideal conditions for P. pyri and allowed high population densities to develop. Feeding and performance experiments indicated that cherry, birch, oak and hornbeam were most susceptible to P. pyri, whereas field maple, hawthorn, rowan, lime and especially ash were resistant. Adult female P. pyri emerged in May reproductively immature and fed on tree foliage for 15.9±0.9 days before laying their first batch of eggs. Adults lived for 33.3±1.5 days, on average, and females laid a mean of 191.9±34.5 eggs (maximum = 589) during their lifetime. Eggs hatched after 16-20 days. During 2003 and 2004, 11-16% of adult P. pyri were parasitised by Pygostylus falcatus (Hymenoptera: Braconidae) and 19-29% were parasitised by Rondania fasciata (Diptera: Tachinidae). [ABSTRACT FROM AUTHOR]

1 The green spruce aphid,Elatobium abietinum, is an important defoliator of Sitka spruce in the U.K. However, it is usual for years in which highE. abietinumpopulations occur to be followed by a year with low aphid densities. The possibility that the performance ofE. abietinumis reduced on previously infested Sitka spruce, and that this is the cause of year-to-year fluctuations in population density, was investigated by comparing population development and the growth rate of individual aphids on experimentally defoliated trees.2 Separate experiments were performed to determine whether aphid performance was reduced either in the autumn immediately after defoliation in the spring, or was reduced in the spring of the next year. Different rates of initial defoliation on trees used to test aphid performance were created by artificially infesting the trees with aphids in the spring before the experiments, and varying the time of infestation.3 Population development and the mean relative growth rate (MRGR) of individual aphids on previously defoliated and undefoliated Sitka spruce did not differ significantly in the spring of the next year. No differences were observed in the nutrient content of the 1-year-old needles of previously defoliated or undefoliated trees at this time.4 In the autumn and winter immediately after spring defoliation, aphid MRGR was significantly higher on trees that had been heavily defoliated earlier in the season compared with trees that had been lightly defoliated. However, the difference in MRGR decreased over the winter period. Nitrogen, phosphorous and potassium concentrations were 9.4–12.2% higher, at the beginning of the autumn, in the current year needles of heavily defoliated trees than in the current year needles of lightly defoliated trees.5 The experiments indicate that high populations ofE. abietinumin the spring do not induce any defensive mechanisms in Sitka spruce that adversely affect subsequent generations of the aphid. By contrast, the results suggest that high spring densities of the aphid improve the nutritional quality of the current year's foliage for autumn generations. [ABSTRACT FROM AUTHOR]

Green spruce aphid (Elatobium abietinum) is the main defoliator of Sitka spruce in the UK, but there is a lack of quantitative data on its effects on tree growth which can be used to predict its impact on current and future timber yields. Consequently. in 1992, the UK Forestry Commission set up a long-term field experiment in Hafren Forest, Wales, to determine the effects of E. abietinum, and root aphids ( Pachypappa and Pachypappella spp.) on the growth of young Sitka spruce plantations. The experiment included four treatments in which natural populations of E. abietinum and root aphids were maintained or were excluded by insecticides, and a fifth treatment in which E. abietinum densities were raised artificially. Natural aphid populations were low during 1992--1995, precluding analysis of the impact of root aphids, but E. abietinum in the enhanced population treatment reached, in June 1994, densities equivalent to a moderate-severe natural outbreak (35--90 aphids - 100 needles-1 on upper shoots). Needle fall was strongly correlated with E. abietinum density and the heavily infested trees lost, on average, 38.5% of their older (1991--1993) needles. This was associated with a 22--23% reduction in leader length in 1994 and a 11--13% reduction in tree height. Aphids and defoliation were concentrated at the tops of the trees and decreased toward thebases, and a similar pattern was observed in relative reductions in shoot growth. This suggested a local influence of aphids or defoliation on shoot growth within the canopy, but such effects could not be distinguished from a response of the trees to the overall rate of damage. Change, in needle size following infestation were not correlated with shoot growth and indicated a differential effect of aphid infestation on shoot and needle development. Continued monitoring of the experiment over the next 2--3 yr should reveal whether further, longer-term changes in shoot and needle production contribute to the restorat [ABSTRACT FROM AUTHOR]

Epidemiological studies have consistently linked exposure to PM 2.5 with adverse health effects. The oxidative potential (OP) of aerosol particles has been widely suggested as a measure of their potential toxicity. Several acellular chemical assays are now readily employed to measure OP; however, uncertainty remains regarding the atmospheric conditions and specific chemical components of PM 2.5 that drive OP. A limited number of studies have simultaneously utilised multiple OP assays with a wide range of concurrent measurements and investigated the seasonality of PM 2.5 OP. In this work, filter samples were collected in winter 2016 and summer 2017 during the atmospheric pollution and human health in a Chinese megacity campaign (APHH-Beijing), and PM 2.5 OP was analysed using four acellular methods: ascorbic acid (AA), dithiothreitol (DTT), 2,7-dichlorofluorescin/hydrogen peroxidase (DCFH) and electron paramagnetic resonance spectroscopy (EPR). Each assay reflects different oxidising properties of PM 2.5 , including particle-bound reactive oxygen species (DCFH), superoxide radical production (EPR) and catalytic redox chemistry (DTT/AA), and a combination of these four assays provided a detailed overall picture of the oxidising properties of PM 2.5 at a central site in Beijing. Positive correlations of OP (normalised per volume of air) of all four assays with overall PM 2.5 mass were observed, with stronger correlations in winter compared to summer. In contrast, when OP assay values were normalised for particle mass, days with higher PM 2.5 mass concentrations (μgm -3 ) were found to have lower mass-normalised OP values as measured by AA and DTT. This finding supports that total PM 2.5 mass concentrations alone may not always be the best indicator for particle toxicity. Univariate analysis of OP values and an extensive range of additional measurements, 107 in total, including PM 2.5 composition, gas-phase composition and meteorological data, provided detailed insight into the chemical components and atmospheric processes that determine PM 2.5 OP variability. Multivariate statistical analyses highlighted associations of OP assay responses with varying chemical components in PM 2.5 for both mass- and volume-normalised data. AA and DTT assays were well predicted by a small set of measurements in multiple linear regression (MLR) models and indicated fossil fuel combustion, vehicle emissions and biogenic secondary organic aerosol (SOA) as influential particle sources in the assay response. Mass MLR models of OP associated with compositional source profiles predicted OP almost as well as volume MLR models, illustrating the influence of mass composition on both particle-level OP and total volume OP. Univariate and multivariate analysis showed that different assays cover different chemical spaces, and through comparison of mass- and volume-normalised data we demonstrate that mass-normalised OP provides a more nuanced picture of compositional drivers and sources of OP compared to volume-normalised analysis. This study constitutes one of the most extensive and comprehensive composition datasets currently available and provides a unique opportunity to explore chemical variations in PM 2.5 and how they affect both PM 2.5 OP and the concentrations of particle-bound reactive oxygen species., Competing Interests: Competing interests. The authors declare that they have no conflict of interest.

A survey of 801 poplar trees in central east England in 1999 demonstrated a correlation between crown dieback and infestation by hornet clearwing moth (Sesia apiformis), induced by a period of drought in 1995-1996. To determine whether trees colonised by S. apiformis would subsequently deteriorate and die or whether they could recover despite infestation and damage to the stem, all trees in the original survey were re-assessed in 2001, 2003 and 2005. The repeat surveys showed that trees with 70% or less crown dieback in 1999 replaced their canopy and generally improved by 2005, irrespective of the numbers of S. apiformis in the stem, whereas trees that had 75% or more crown dieback in 1999 either died or declined further. The presence of S. apiformis did not prevent tree recovery, and there was little evidence that infestation slowed the rate of recovery. Populations of S. apiformis, measured in terms of the numbers of adult emergence holes visible in the base of the trees, decreased between 2001 and 2005 at the same time as the amount of dieback visible in the canopy of the poplars markedly decreased. However, the fall in numbers of emergence holes at this time reflected a decline in larval establishment 2-3 years earlier, and indicated that the moth population had responded to a more rapid restoration in the internal state of the trees, which was not reflected immediately by the gradual replacement of dead branches and reduction in dieback symptoms.