Is terrestrial plant import from East Asia into countries in the EPPO region a potential pathway for new emerging invasive alien plants?

Pathway analysis represents an effective means of identifying emerging invasive alien species. For plants, a significant number of invasions have been caused by plant species originally voluntary introduced as ornamentals. The pathway analysis for terrestrial ornamental plants imported from East Asia has been undertaken to provide information on the imports and to identify emerging terrestrial invasive alien plants. Data for terrestrial ornamental plants imported from East Asia into Austria, France, Italy, the Netherlands and Turkey was assembled at the genus level. Thousands of species of plants for planting are imported from East Asia in very large volumes. However, despite the fact that the data could only been analyzed at the genus level, it is considered that only a very limited number of taxa would become invasive. The potentially invasive alien species are already widely available in European nurseries and are principally produced within the European Union.     

Is Change in Electrical Potential or pH a Hatching Signal for Heterodera glycines?

ABSTRACT This study explored the possibilities that changes in the egg shell/lipid layer electrical potential or pH communicate external hatching conditions to the Heterodera glycines second-stage juvenile (J2) within the mature egg and that electrophysiology could measure effects of chemicals on emergence. Potentials were measured following application of the emergence inducers (ZnSO(4) and ZnCl(2)), ions that do not affect emergence, or synthetic emergence inhibitors. Results were compared with pH measurements and emergence bioassays. Healthy appearing eggs had negative resting potentials. Application of ZnSO(4) caused a smooth depolarization. However, eggs containing J2 and immature eggs depolarized to a similar degree when ZnSO(4) was added. In addition, ZnSO(4), synthetic emergence inhibitors, and CaCl(2) caused similar depolarization, and some depolarization was measured in dye-permeable eggs and empty shells. Results suggest that change in cation surface charge contributed to depolarization and that Cl penetrated the egg shell/lipid layer without causing potential changes. In bioassays, zinc consistently stimulated emergence to a greater degree than H(2)O, other cations, or buffers, and counteracted emergence inhibitors. Zinc-caused emergence stimulation was independent of pH. In summary, it is concluded that depolarization and pH are not emergence signals and electrophysiology is unlikely to measure effectiveness of emergence stimulators or inhibitors.     

Do aeolian deposits and sand encroachment intensity shape patterns of vegetation diversity and plant functional traits in desert pavements?

The effects of sand encroachment on composition, diversity, and functional patterns of vegetation in drylands are rarely studied, and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation. This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts) in the Sahara Desert of Algeria. Plants were sampled and analyzed in three desert pavements with different levels of sand encroac...     

Soil substrate as a cascade of capillary barriers for conserving water in a desert environment:lessons learned from arid nature

Interaction between soil pedogenesis, subsurface water dynamics, climate, vegetation and human ingenuity in a desert environment has been found to result in a unique ecohydrological system with an essentially three dimensional sedimentation structure in the bed of a recharge dam in Oman. A 3-D array of silt blocks sandwiched by dry sand-filled horizontal and vertical fractures was studied in pot experiments as a model of a natural prototype. Pots are filled with a homogenous sand-silt mixture(control) or artificially structured(smart design, SD) soil substrates. Rhodes grass and ivy(Ipomea, Convolvulaceae) were grown in the pots during the hottest season in Oman. Soil moisture content(SMC) was measured at different depths over a period of 20 days without irrigation. SD preserved the SMC of the root zone for both ivy and grass(SMC of around 25%–30% compared to 10% for control, 3 days after the last irrigation). Even after 20 days, SMC was around 18% in the SD and 7% in the control. This, similar to the case of a natural prototype, is attributed to the higher upward capillary movement of water in control pots and intensive evaporation. The capillary barrier of sand sheaths causes discontinuity in moisture migration from the micro-pores in the silt blocks to sand pores. The blocks serve as capillarity-locked water buffers, which are depleted at a slow rate by transpiration rather than evaporation from the soil surface. This creates a unique ecosystem with a dramatic difference in vegetation between SD-pots and control pots. Consequently, the Noy-Meir edaphic factor, conceptualizing the ecological impact of 1-D vertical heterogeneity of desert soils, should be generalized to incorporate 3-D soil heterogeneity patterns. This agro-engineering control of the soil substrate and soil moisture distribution and dynamics(SMDaD) can be widely used by desert farmers as a cheap technique, with significant savings of irrigation water.     

Is acetyl/butyrylcholine specificity a marker for insecticide‐resistance mutations in insect acetylcholinesterase?

Substrate specificity has been widely studied in vertebrate cholinesterases and it has been shown that two phenylalanines in the acyl pocket of acetylcholinesterase govern the acceptance of the acetyl/butyryl moiety of the choline esters. As an insecticide‐resistance mutation has been evidenced in the acyl pocket of Drosophila melanogaster and Musca domestica acetylcholinesterase we investigated the possibility of linking changes in acetyl/butyrylthiocholine specificity with mutations in insect acetylcholinesterase. We thus analyzed the effect of 28 mutations in Drosophila enzyme on acetyl/butyrylthiocholine, N‐methyl/N‐propyl‐carbamates and ethyl/methyl‐paraoxon preference. It appeared that the highest changes on acetyl/butyrylthiocholine and N‐propyl/N‐methyl‐carbamates preference were due to mutations in the acyl pocket. Nevertheless, other insecticide‐resistance mutations, not located in the acyl pocket, also modified these substrate preferences. Moreover, the effect of mutations in the acyl pocket was hidden when some other insecticide‐resistance mutations were combined in the enzyme. Consequently, acetyl/butyrylthiocholine preference alteration cannot be used as a marker to localize a mutation in the insect AChE. © 2000 Society of Chemical Industry     

Is the temporary grazing exclusion a good management alternative for arid peatlands?

Highland peatlands are one of the most fragile ecosystems in the world. These ecosystems have vital nutritional importance for livestock, however previous research has indicated that intensive grazing could negatively affect these communities, requiring the application of temporary grazing exclusion to restore the health of the peatland. The objective of our study was to evaluate the effect of grazing exclusion on plant allocation strategy and carrying capacity of Oxychloe andina Phil. The plant traits of O. andina were quantified through measurements of specific leaf area (SLA) and leaf dry matter content (LDMC). We estimated the carrying capacity through livestock censuses and vegetational transects. SLA was found to be greater in grazed conditions than in ungrazed conditions (p?=?0.0194) at five months after the application of treatments. Additionally, greater productivity associated with greater LDMC in March was observed under conditions of grazing exclusion (p?=?0.0306). Production estimates of O. andina reached 4816?kg of dry matter (DM) distributed over an area of 9.84?ha, which was equivalent to 489?kg DM of O. andina DM ha^?1. Using DM production as a proxy of the peatland and considering the average vegetation cover of 70%, the peatland produces an estimated of 1370?kg DM year^?1. The temporary grazing exclusion enhanced the productivity of O. andina. However, depending on DM production in relation to grazing demand, there is a possibility of exceeding the animal load for this plant species.     

Powdery mildew of Arabidopsis thaliana: a pathosystem for exploring the role of silicon in plant–microbe interactions

Silicon (Si) has been used in agriculture to protect plants against disease for hundreds of years and its prophylactic effects in monocots and dicots are well documented. The mechanisms by which Si exerts its protective effects in planta, however, are uncertain and presently the subject of debate. In this study, we sought to determine if Arabidopsis thaliana could be used to clarify the role of Si in plant–pathogen interactions. Accordingly, X-ray microanalysis mapping, light microscopy, scanning and transmission electron microscope techniques were used to examine the leaves of Si− fed A. thaliana plants inoculated with the powdery mildew fungus, Erysiphe cichoracearum. The results of this study demonstrate for the first time, that A. thaliana is a species that absorbs Si and that the incidence of powdery mildew disease for Si− fed plants is significantly lower compared to control plants. In particular, treatment with Si appeared to induce the production of an electron-dense, fungitoxic substance that accumulated within and around the collapsed fungal haustoria of infected epidermal cells within the leaves of disease-resistant plants. These results with Arabidopsis corroborate recent observations in other non-related species and support the emerging theory that the mechanisms by which Si imparts resistance to plants are complex and are not entirely explained by the traditionally proposed role of Si as a reinforcer of mechanical resistance. Collectively, the findings of the present study have established the Arabidopsis thaliana-Erysiphe cichoracearum pathosystem as a valid model to investigate the role of Si in plant–microbe interactions.     

Is there evidence for post-epidemic attenuation in the Dutch elm disease pathogen Ophiostoma novo-ulmi?

The first pandemic of Dutch elm disease (DED) in Europe and North America caused by the introduced Ophiostoma ulmi began in the early 1900s but declined unexpectedly in Europe from the 1930s onwards after killing 30–40% of the elms. Later a second pandemic caused by the much more aggressive Ophiostoma novo-ulmi spread across the same areas and by 1990 most of Britain's c. 30 million mature elms had died. During the second pandemic, O. novo-ulmi acquired debilitating viruses and changed from being largely clonal to highly heterogeneous through horizontal transfer of novel, sometimes deleterious, genes from O. ulmi. In the post-epidemic period a new disease dynamic has emerged, with millions of small recruitment elms repeatedly attacked by sequential cycles of disease. This study investigated the possibility of pathogenic attenuation in O. novo-ulmi as the epidemic has progressed. Isolates collected from the three original outbreak areas in Britain in 1982–3 (early post-epidemic period) and 2011 (advanced post-epidemic) were compared for two fitness components: pathogenic aggressiveness and in vitro growth rate. Mean aggressiveness of the 2011 isolates to clonal English elm (Ulmus procera) proved not to differ significantly from that of the 1982 isolates, either overall or within each outbreak area. Similarly, the mean growth rates of the 1982 and 2011 samples showed no differences. The implications of these findings are discussed in relation to the future of the current DED pandemic in Europe, the decline of the first pandemic, and the difficulty of drawing parallels between different tree–pathogen systems.     

Is a helper factor necessary for infection of cowpea protoplasts with blackeye cowpea mosaic virus?

Samenvatting Bij inoculatie van mesofyl protoplasten van cowpea met een zeer infectieuze, gezuiverde suspensie van blackeye cowpea mosaic virus (BlCMV), een potyvirus, kon een infectie niet worden geconstateerd. Wanneer echter de bovenstaande vloeistof, verkregen na centrifugering bij laag toerental van sap van BlCMV-geînfecteerde planten, als inoculum werd gebruikt, dan kon vermeerdering van het virus in de protoplasten worden vastgesteld door middel van infectiositeitsproeven, immunofluorescentie en elektronenmicroscopie. Werd deze bovenstaande vloeistof, ontdaan van zijn infectiositeit, hetzij door bestraling met UV-licht, hetzij door centrifugering bij hoog toerental, en vervolgens gemengd met gezuiverd virus, dan trad er geen infectie van de protoplasten op.     

Bt-transgenic crops: just another pretty insecticide or a chance for a new start in resistance management?

Transgenic insect-resistant crops carrying genes from Bacillus thuringiensis were grown commercially for the first time in 1996 amid considerable public controversy about resistance management. Several resistance management strategies have been proposed for Bt-transgenic crops. The most promising with currently available technology is the use of refuges of non-transgenic crops, augmented where possible with high toxin expression in the plant and avoiding mosaics of different toxins and pesticides. One problem is that the refuge sizes that are seen as commercially and practically acceptable are generally too small to provide a comfortable margin for the delay of resistance. A promising long-term strategy for delaying resistance, and one which is more forgiving on refuge size, is the pyramiding of two or more insecticidal genes in the same plant. The critical limiting factor to resistance management for transgenic crops will be implementation, which will require cooperation among companies. ©1997 SCI     

Is there need for leaf-galling grape phylloxera control? Presence and distribution of Dactulosphaira vitifoliae in Swiss vineyards

Grape phylloxera (Dactulosphaira vitifoliae, FITCH) was a major pest in Vitis vinifera grape production in the late 19th and early 20th century in Europe. Roots of V. vinifera varieties are susceptible to D. vitifoliae attack whereas the leaves are not affected. The pest has been controlled by using American grapevine varieties as rootstocks. However, in recent years, grape producers have reported higher incidences of leaf galls induced by D. vitifoliae on V. vinifera leaves. Research on the occurrence of D. vitifoliae on grapevine leaves and roots has shown that D. vitifoliae is present in all wine-growing regions of Switzerland. In more than 80% of vineyards claiming to be infested, D. vitifoliae was found on leaves of varieties with interspecific crosses in their parentage. Three locations with leaf-galling individuals on V. vinifera were detected. D. vitifoliae individuals were found emerging from soil potentially associated with the commonly used rootstock varieties, which are assumed to be phylloxera tolerant. As climate change may necessitate the relocation of some viticultural areas to new wine-growing regions, there will be a greater need to control D. vitifoliae on leaves of interspecific crosses and the inspected planting material to limit further spread of the pest.     

The β-tubulin Gene is a Useful Target for PCR-based Detection of an Albino Ophiostoma piliferum Used in Biological Control of Sapstain

The potential of Cartapip, an albino Ophiostoma piliferum, as a biocontrol agent against sapstain in logs has been tested in Germany. To detect the albino strain in field-tested wood, the usefulness of the -tubulin gene as a target region for developing PCR-based assays was evaluated with 102 strains of O. piliferum and 31 strains of other wood-inhabiting species. A partial -tubulin gene sequence of O. piliferum strains from different geographic origins was amplified by PCR and analyzed by restriction enzyme digestions and DNA sequencing. Variation in size and nucleotide sequences was found in intron regions indicating that intraspecific variation is present in the -tubulin gene. Consequently, -tubulin gene-derived PCR methods using PCR–RFLP patterns generated by HinfI and SpeI and sequence-specific primers Cat1 and Cat2, were developed and their specificity for Cartapip was accessed with field-tested logs and lumber. The -tubulin gene-based PCR methods were found to be valuable tools for rapid and reliable identification of Cartapip in field-tested logs and lumber in Germany. Specificity tests against other wood-inhabiting species and wild type O. piliferum strains from diverse nations showed that the Cat1 and Cat2 primers have potential to be used in other European countries, New Zealand, Alberta and British Columbia.     

The debate on a loss of biodiversity: can we derive evidence from the monitoring of major plant pests and diseases in major crops?

Journal of Plant Diseases and Protection - The European commission directive EC 128/2009 calls for monitoring pests and pathogens of major crops. The monitoring data may be analysed for trends over...     

Is the current state of the art of weed monitoring suitable for site‐specific weed management in arable crops?

Weed monitoring is the first step in any site‐specific weed management programme. A relatively large variety of platforms, cameras, sensors and image analysis procedures are available to detect and map weed presence/abundance at various times and spatial scales. Remote sensing from satellites or aircraft can provide accurate weed maps when the images are obtained at late weed phenological stages. Cameras located on unmanned aerial vehicles (UAVs) have been shown to be adequate for early‐season weed detection in a variety of wide‐row crops, providing images with relatively high spatial resolutions. Alternatively, weed detection/mapping systems from ground‐based platforms can achieve even higher resolutions using a variety of non‐imaging and imaging technologies. These ground systems are suited, in some cases, for real‐time site‐specific weed management. Despite this rich arsenal of technologies, their commercial adoption is, apparently, low. In this study, we describe the state of the art of remotely sensed and ground‐based weed monitoring in arable crops and the current level of adoption of these technologies, exploring major constraints for adoption and trying to identify research gaps and bottlenecks.     

The EFSA assessment of Trichilogaster acaciaelongifoliae as biocontrol agent of the invasive alien plant Acacia longifolia: a new area of activity for the EFSA Plant Health Panel?

This paper summarizes the first assessment by the European Food Safety Authority (EFSA) Plant Health (PLH) Panel of a biological control agent (BCA) of an invasive plant. This followed a request by the European Union (EU) Commission to assess the risk to plant health in the EU of an intentional release of the bud‐galling wasp Trichilogaster acaciaelongifoliae for the control of Acacia longifolia. The EFSA PLH Panel also published a statement on the process of assessing the risk of the intentional releases of BCAs of invasive alien plants. Trichilogaster acaciaelongifoliae feeds on A. longifolia and Acacia floribunda. Acacia longifolia is an invasive alien plant species that has a negative effect on biodiversity and ecosystems in Portugal, whereas A. floribunda is not invasive in the EU. Both species are cultivated as ornamental plants in some EU countries. Climatic conditions in the EU are suitable for establishment of T. acaciaelongifoliae where host species are present. This BCA is moderately likely to spread in the EU by natural means, but could be intentionally moved to control A. longifolia in other locations. Its potential effects on invasive A. longifolia and on the cultivated ornamentals were assessed. The EFSA PLH Panel has shown with this work how such advice could be provided in the European Union.     

Banning of methyl bromide for seed treatment: could Ditylenchus dipsaci again become a major threat to alfalfa production in Europe?

In Europe, the stem and bulb nematode Ditylenchus dipsaci has been listed as a quarantine pest by EPPO: without any control, it may cause complete failure of alfalfa crops. Movement of nematodes associated with seeds is considered to be the highest‐risk pathway for the spread of this pest. Since the 2010 official withdrawal of methyl bromide in Europe, and in the absence of any alternative chemical, fumigation of contaminated seed batches is no longer possible, which makes the production of nematode‐free alfalfa seeds difficult to achieve and leads to unmarketable seed batches. Thermotherapy is being considered as a realistic alternative strategy, but its efficiency still remains to be validated. The combination of the currently available methods (i.e. use of resistant cultivars, seed production according to a certification scheme, mechanical sieving, seed batch inspection) could significantly reduce the likelihood of seed contamination. However, it does not guarantee a total eradication of the nematode. Although it is already widely distributed all over Europe, reclassification of D. dipsaci as a regulated non‐quarantine pest to reduce the possibility of further introductions and the rate of spread of this pest appears to be a risky strategy because of the lack of up‐to‐date documented data to evaluate damage thresholds and determine acceptable tolerance levels. [[ArtCopyrightmsg]]