Monooxygenase mediated pyrethroid detoxification in sea lice (Lepeophtheirus salmonis)

The role of monooxygenases in detoxification of the pyrethroids cypermethrin and deltamethrin was examined. Four strains of sea lice (Lepeophtheirus salmonis Krøyer) with normal or moderately reduced sensitivity towards the pyrethroids were tested in bioassays by exposure to the pyrethroid alone and in combination with an oxygenase inhibitor, piperonyl butoxide (PBO). The normal (baseline) sensitivity was considered as the sensitivity range for the two most sensitive strains. Pre‐treatment with PBO elevated the sensitivity (P < 0.01) compared with groups exposed to the pyrethroid only. A positive, but not statistically significant, correlation between the activity of haem peroxidases and the pyrethroid concentration immobilizing 50% of the parasites was demonstrated (ρ = 0.500 for deltamethrin and ρ = 0.310 for cypermethrin). The results indicate that cytochrome P450 monooxygenases are involved in detoxification of pyrethroids in sea lice. ¹⁴C‐Deltamethrin was absorbed in a lesser amount in a group of sea lice exposed to a mixture of the compound and PBO than in a group exposed to ¹⁴C‐deltamethrin alone. A significant difference could be demonstrated both immediately after exposure (P < 0.01) and 24 h after exposure (P < 0.05). No significant differences were found between groups pre‐treated with PBO and groups exposed to ¹⁴C‐deltamethrin only. ¹⁴C‐Deltamethrin was taken up mainly through the cuticle, especially the cuticle on the extremities of the ventral surface, and subsequently distributed throughout the body of the parasite. Copyright © 2005 Society of Chemical Industry     

Strategies for non-chemical weed control on public paved areas in Denmark

To be proactive in minimizing pesticide use, the public authorities in Denmark agreed in 1998 to phase out the use of pesticides on publicly owned areas by the end of 2002. A part of the agreement was an increasing focus on research into and development of new methods and implements for non-chemical weed control on paved areas. Due to a large increase in the costs of non-chemical weed control, the park authorities have to put the different types and locations of paved areas in order of priority to optimize the weed control effort. The present authors divided the paved areas into five weed control levels, dependent on placement, quality and use. For the 3 years 1999-2001, experiments with different non-chemical weed control methods were conducted on pavements at six locations in Denmark. The aim was to test the reaction of the weeds to different treatments and strategies. The efficacies of the methods were evaluated by analysis of digital images to estimate the fraction of the paved area covered with green vegetation (weed coverage). The weed coverage was used as the dependent variable in the subsequent statistical analysis. The independent variables in the model were incoming radiation, wear, area of joints in the pavement, the dying process of the weeds and the number of runs/applied energy of the mechanical or thermal weed control methods, respectively. The estimated parameters from the statistical model were used to build a simulation model, which was used to optimise five weed control strategies to fulfil the suggested weed control levels. In the suggested strategy for maximum weed control, 12 thermal weeding applications at 2-week intervals are suggested. The 'clean-up' strategy is based on one weed-brushing in late spring or early autumn.     

Plant availability of catch crop sulfur following spring incorporation

Catch crops might reduce sulfate leaching and thereby increase the overall sulfur (S)‐use efficiency in crop rotations. At two experimental sites in Denmark (a sandy loam and a coarse sand), S uptake of catch‐crop species was measured. Furthermore, net release of S following incorporation of this material (S contents 0.13%–1.03%, C:S ratios of 40–329, and lignin contents of 1%–10.8%) was investigated in a pot experiment with spring barley in sandy soil. The catch crops showed huge differences in their ability to sequester S. The best catch crops (legumes on sandy loam), sequestered 10–12 kg S ha^–1, and the poorest catch crops (ryegrass and sorrel on coarse sand) sequestered less than 3 kg S ha^–1. The S‐mineralization rates were highest for crucifers (57%–85% of total S added) and lowest for legumes (up to 46% of total S added). Differences can partly be explained by the C:S ratio, whereas no significant relationship was found with the lignin content of the incorporated catch crops. Catch crops may help to avoid S deficiency and increase synchrony between plant demand and available soil S in a crop rotation. However, the release of S will not fulfil the need of S‐demanding crops and even for cereals, the mineralization will most often only make a contribution. In the case of legume catch crops, it is advisable to use a supplemental S source.     

Trichothecene production by Trichoderma brevicompactum

Trichoderma brevicompactum, T. viride, T. harzianum, T. atroviride, T. longibrachiatum, T. erinaceum, T. citrinoviride, and Hypocrea lutea were screened for production of trichothecenes after growth on one or several solid and liquid media. Trichothecenes were detected by liquid chromatography combined with online UV/vis spectroscopy and electrospray high-resolution mass spectrometry. T. brevicompactum produced trichodermin and/or harzianum A on all media investigated, with liquid media yielding the largest amounts. Detection of octa-2Z,4E,6E-trienedioic acid in the harzianum-A-producing strains indicated that harzianum A was synthesized directly by esterification of trichodermol with octa-2Z,4E,6E-trienedioic acid. Both the T. viride strain from which trichodermin was originally isolated and the T. harzianum strain from which harzianum A was originally isolated were shown to belong to T. brevicompactum based on four independent criteria: metabolite profiles, micromorphology, macromorphology on yeast extract sucrose agar and potato dextrose agar, and DNA sequences of the ITS1/ITS2 regions of the nuclear ribosomal DNA.     

Regional differences in harvesting levels and wood-based employment in Norway

In this paper, a statistical framework based upon shift-share analysis is employed to analyse regional differences in Norway regarding changes in harvesting levels and number of full-time equivalent employees in wood processing. Changes in harvesting levels and employment differ between regions. A tendency found is that there has been a moderate centralisation in the period 1990–2000 with respect to harvesting levels. The analysis indicates that remote municipalities harvest relatively more in periods with a high harvesting intensity, while the harvesting level is more evenly distributed among the regions in other periods. There is, however, no clear picture whether there has been a centralisation or decentralisation regarding woodbased employment. Differences between regions may therefore be explained by structural factors, for example the degree to which firms in a particular region concentrate on production of bulky commodities or more customeroriented niche production.     

Can fishing communities escape marginalisation? Comparing overfishing,environmental pressures and adaptation in Thailand and the Philippines

In this article, we compare four fishing‐based areas in Thailand and the Philippines to examine if and how small‐scale fishing communities are able to escape marginalisation. Three questions guide our inquiry: (i) How have fishing communities been affected by overfishing, climate change and other pressures? (ii) What adaptive strategies have these communities employed to mitigate socio‐economic and environmental challenges? (iii) What has been the impact of these strategies on (escaping) marginalisation? Through a survey of 393 fishing‐based households and semi‐structured interviews with 59 key informants we find an uneven mixture of drivers, strategies and impacts. Respondents varyingly attribute declining fish catch to illegal fishing, overfishing, population increase, climate change and pollution. The case studies illustrate various degrees of adaptive successes that result from integration of top‐down and bottom‐up initiatives, and availability and access to livelihood strategies. However, the impact of adaptive strategies on overcoming marginalisation remains meagre and constrained by, among others, the power of illegal and commercial fishing and the absence of integrated spatial planning. We call for policy interventions and further research that takes into account the integration of top‐down and bottom‐up institutions, and the multiple dimensions and spaces of the drivers that shape fisherfolk marginalisation.     

Secondary metabolite and mycotoxin production by the Rhizopus microsporus group

Fast-growing Zygomycetes, most notably Rhizopus oligosporus, are traditionally used in many food fermentations, for example, for soybean tempeh production. R. oligosporus is considered to belong to the Rhizopus microsporus group. Certain R. microsporus strains have been reported to produce either the pharmaceutically active rhizoxins or the highly toxic rhizonins A and B. In this study was investigated the formation of secondary metabolites by R. microsporus, R. oligosporus, and Rhizopus chinensis grown on a wide range of different semisynthetic and natural substrates. Liquid chromatography, combined with photodiode array detection and high-resolution mass spectrometric techniques, was used to identify secondary metabolites. Growth on maize, brown rice, and Pharma agar gave both the highest amounts and the maximum diversity of rhizoxins and rhizonins. Rhizoxins were produced by all four R. microsporus strains, whereas only one strain produced rhizonins. The six R. oligosporus and four R. chinensis strains investigated did not produce any of these two classes of metabolites.