Seasonal emergence of weeds in cultivated soil in New Zealand

Patterns of seedling emergence of ten weed species from soil cultivated at intervals of approximately one month are described. All species examined showed clearly defined emergence patterns. Polygonum persicaria L. seedlings emerged in spring and early summer. Seedlings of Chenopodium album agg., Portulaca oleracea L. and Solanum nigrum L. emerged in late spring, summer and early autumn.Plantago major L., Rumex spp. (mostly R. obtusifolius L.) and Trifolium spp. (mostly T. repens L.) emerged mostly in spring and early summer. Coronopus didymus (L.) Sm. and Juncus bufonius L. tended to emerge in both autumn and spring.Veronica persica Poir. emerged in spring, summer and autumn. Close similarity between emergence patterns in New Zealand and northern Europe, despite differences in rainfall and temperature, suggests that annual dormancy:nondormancy cycles of seeds buried in the soil are largely responsible for seedling emergence patterns. In New Zealand, seedling emergence tended to be more spread out than in Europe, although seasonal patterns were still distinct. Further work on dormancy cycles in these species would be useful, as would a comparison of the factors inducing and breaking dormancy of comparable seed populations in northern and southern Europe and New Zealand. When seeds were left buried for several years before being encouraged to germinate, seedling emergence patterns tended to be of smaller amplitude, although the overall patterns were still very similar.     

Outbreaks and Damage by the Field Vole,Microtus agrestis (L.), since World War II in Europe1

The field vole, Microtus agrestis (L.), is a major pest in horticulture and forestry in all Scandinavian countries, and an important forestry pest in certain regions in central Europe. The most common type of damage is girdling trunks of cultivated trees, usually under the snow cover. In horticulture, the apple tree is the commonest subject of injury, while, in forestry, several deciduous and conifer species are attacked. In Finland and Norway, the garden industry has suffered most, while, in Sweden, the problems are predominantly in forestry. In central Europe, M. agrestis is a forestry pest only. Summation of all losses due to the field vole since World War II amounted to somewhere between 50 and 100 million US Populations of M. agrestis normally undergo cyclic fluctuations. However, comparison of the periodicity of outbreaks in different areas reveals variations, 3 to 4-year intervals dominating in the Scandinavian countries, while the interval in central Europe is generally somewhat shorter. No overall synchrony exists over the geographical range of the species. Present knowledge concerning the demography and habitat dynamics of M. agrestis is briefly reviewed. Current possibilities for preventing damage by M. agrestis are much dependent on the individual value of the potential subjects of injury. High value stands, like apple gardens or seed orchards of forest trees, can be protected by means of mechanical guards. However, current means of combating damage in forest plantations are badly limited. Surface spraying with toxaphene and poison baits is practised in central Europe, while, in the Scandinavian countries (except Denmark), no chemical means are used today. Development of new compounds to be used as surface sprays, or specific baits for M. agrestis, is urgently needed. Research on bio-control methods should also be intensified.     

Glue barriers reduce earwig damage on apricots in north-western Italy

The European earwig, Forficula auricularia L. (Dermaptera: Forficulidae), is a well-known species that is cosmopolitan and present throughout Europe. Due to its omnivorous feeding behaviour, this species can act as a generalist predator, preying on several top fruit pests, but also as a pest causing shallow gouges or holes in stone and soft fruits such as apricots, strawberries, raspberries or blackberries. In Piedmont (NW Italy), significant fruit damage has been observed lately in apricot orchards where earwigs fed on ripening fruits and made a considerable part of the produce unmarketable. In this study, we sampled earwig populations in three apricot orchards in Piedmont and tested the effectiveness of glue barriers applied to the tree trunks in reducing both earwig density in the canopy and fruit damage. The arboreal glues Rampastop® and Vebicolla® were tested both in the field and laboratory trials. Glue barriers demonstrated to be effective control measures, significantly reducing earwig abundance in the canopy and fruit damage. Rampastop® gave better results on old trees with a very rough and cracked bark, since in that case Vebicolla® could not perfectly bond with the trunk.     

Virulence of the invasive ash pathogen Hymenoscyphus fraxineus in old and recently established populations

Following its introduction from Asia in the 1990s, the ascomycete Hymenoscyphus fraxineus has caused a severe dieback of Fraxinus excelsior in Europe. In this study, the virulence of 200 H. fraxineus isolates were assessed and compared. These isolates equally represented (i) two geographically distant populations with a different disease history (Switzerland, recently established populations at the epidemic front versus Lithuania, old established populations), and (ii) isolates from two different types of host tissue (necrotic bark lesions as dead‐end tissue versus fallen leaf petioles as primary host tissue). Inoculations conducted on 3‐year‐old F. excelsior seedlings showed that the vast majority of the isolates (98%) were able to induce necrotic bark lesions after 10 months. Although a high variation in virulence was observed among isolates, no significant differences were detected between the older and the epidemic‐front populations. Decline in virulence of populations of invasive organisms is generally assumed with increasing age of epidemics. However, this does not appear to hold true for H. fraxineus. Either the Lithuanian population is still too young (15 to 20 years old) to show a decline in virulence, or the size of the host population may still not be critical for pathogen survival. Given that bark lesions represent an epidemiological dead end and do not benefit the survival of H. fraxineus, a trend towards reduced ‘bark virulence’ of isolates originating from leaf petioles compared to isolates from the bark lesions was expected. However, such a trend was observed neither in old, nor in recently established populations.     

Genetic diversity of the declining arable plant Centaurea cyanus: population fragmentation within an agricultural landscape is not associated with enhanced spatial genetic structure

Agricultural intensification has recently resulted in the decrease in frequency and abundance of arable weed species. This includes the previously widespread Centaurea cyanus, whose populations are now fragmented and infrequent in western Europe. The consequences of habitat modification and fragmentation in terms of genetic diversity of the remaining populations have not yet been addressed. We used ten microsatellite markers to assess the genetic diversity and genetic structure of populations contained in an agricultural landscape in north‐eastern France. The ten microsatellites were all highly polymorphic. Centaurea cyanus appears to be a genetically variable species, with high levels of genetic diversity within each cultivated field. Genetic structure was investigated using a Bayesian method. The partitioning of the genetic variation into three clusters was not associated with sampling locations, and most individuals were admixed. These results suggest that the cornflower populations investigated may have multiple origins in the past and that genetic variation has been reshuffled by human transportation of seeds. Thus, anthropogenic dispersal associated with farming activities is probably a major factor driving the structure of genetic diversity in arable land plants. Despite low levels of genetic differentiation between populations, fine‐scale spatial genetic structure was observed within populations, suggesting limited local dispersal. We conclude that in areas where C. cyanus has become rare, the recent fragmentation of populations may in the future cause a loss of genetic diversity and even extinction.     

A study on seed population dynamics of three weedy species of Eupatorium

The data on seed population dynamics of three weedy species of Eupatorium, viz. E. adenophwrum Spreng., E. riparium Regel and E. odoratum L. have been presented and discussed in the paper. The seed production and seed populations in soil seed bank were estimated, and the fate of buried seeds in soil was followed over a 2-year period. All the three species of Eupatorium produced a large number of seeds. The seed production of E. riparium per unit area was higher than that of the other two species because of its high population density. In all the three species most of the seeds were found to be present in the top 2 cm of the soil. The viable seed population of the three species of Eupatorium declined exponentially alter their burial in soil showing almost similar mortality patterns. A large proportion of seeds of all the Eupatorium spp. remained under enforced dormancy during their burial in soil with only a small fraction exhibiting induced dormancy. The longevity of the buried seeds increased on account of the dormancy imposed on them. The loss of seeds through degeneration and/or decomposition was rather low.     

From biology to management of Savi's pine vole (Microtus savii)

Savi's pine vole (Microtus savii) is a rodent species of the Cricetidae family, inhabiting southern European agroecosystems. It is considered to be the main cause of rodent‐attributed damage in Italy. To achieve an effective management, detailed knowledge of this species is needed. However, the available information about this species is fragmentary and incomplete. In this paper, the existing knowledge of Savi's pine vole taxonomy, reproduction, population dynamics, habitat and food preferences is reviewed in order to organise available information and identify priority areas of future research. Some of the changes in farming practices that have occurred in recent decades may have increased the impact of Savi's pine vole populations in crop fields. To manage this pest species effectively, an integrated strategy is recommended (involving habitat management, trapping and, when appropriate, the use of rodenticides). The apparent lack of cyclical population outbreaks and the relatively small litter size and long gestation and interpartum period of this species suggest that it could be more manageable than other vole species, while its strict herbivorous diet, stable population size in open habitats and wide distribution seem to indicate it as an ideal model species for risk assessment studies. © 2015 Society of Chemical Industry     

Distribution of <Emphasis Type="Italic">Typhula ishikariensis</Emphasis> Biotype A Isolates Belonging to a Predominant Mycelial Compatibility Group

The distribution pattern and frequency of isolates of a snow mold fungus, Typhula ishikariensis biotype A belonging to a predominant MCG (mycelial compatibility group, referred to as super MCG), were surveyed throughout its habitat from northern Honshu to eastern Hokkaido. About 38 and 14% of isolates examined belonged to super MCG in eastern and central Hokkaido, respectively ; however, super MCG was never found in southern Hokkaido or northern Honshu. These findings imply that T. ishikariensis biotype A consists of two populations in Japan, i.e., one that is distributed in Honshu and southern Hokkaido and lacks super MCG isolates, and the other that includes super MCG isolates and exists in central and eastern Hokkaido. The difference in distribution pattern of the two populations is discussed in terms of geological history during the Pleistocene (2 million to 10 thousand years ago). The tendency of global warming, which alleviates freezing damage, was considered to be responsible for the outbreak of this fungus in eastern Hokkaido. Received 6 December 1999/ Accepted in revised form 9 December 1999     

Correlation between the soil seed bank and weed populations in maize fields

Annual weed populations establish every year from persistent seed banks in the soil. This 3 year study investigated the relationship between the number of weed seeds in the soil seed bank and the resultant populations of major broadleaf and grass weeds in 30 maize fields. After planting the crop, 1 m² areas were protected from the pre-emergence herbicide application. Soil samples were collected soon after spraying to a depth of 100 mm and the weed seeds therein were enumerated. The emerged weed seedlings in the field sampling areas were counted over the following 8 weeks. Up to 67 broadleaf species and five grass weeds were identified, although not all were found at every site and some were specific to a region or soil type. For the most abundant weeds in the field plots, on average 2.1–8.2% of the seeds of the broadleaf species and 6.2–11.9% of the seeds of the grass weeds in the soil seed bank emerged in any one year, depending on the species. Overall, the results showed a strong linear relationship between the seed numbers in the soil and the seedling numbers in the field for all the grasses and for most broadleaf weeds. For some species, like Trifolium repens , only a weak relationship was observed. In the case of Chenopodium album , which had the largest seed bank, there was evidence of asymptotic behavior, with seedling emergence leveling off at high seed numbers. An estimate of the soil seed bank combined with knowledge of the germination and behavior of specific weed species would thus have good potential for predicting future weed infestations in maize fields.     

塔里木河下游植被退化区土壤种子库特征

本文在塔里木河下游选择了四个典型荒漠植被退化区,通过土壤种子库萌发实验,对土壤种子库的基本特征以及与地上植被的关系进行了对比研究。结果表明:1)四个植被退化区土壤种子库总共含有10个物种(属),平均密度1633.33粒/m2。2)四个植被退化区种子库密度总和来看,0-5cm层>5-10cm>层10-30cm层,但在各个研究区中种子库密度的垂直分布异质性差异很大,没有一致的规律。3)各个研究区土壤种子库种子的生活型组成,草本物种密度均明显高于灌木。4)土壤种子库与地上植被的相似性系数在四个研究区均很低;随着退化程度的加重,种子库的密度和物种数均呈现明显的下降趋势,但土壤种子库物种组成的稳定性要高于地上植被。     

Fungicide sensitivity of populations of wheat powdery mildew (Erysiphe graminis f.sp. Tritici) in Central Europe in 1993

In 1993 we observed the sensitivity of wheat powdery mildew populations (Erysiphe graminis DC f.sp. tritici Marchal) from the Czech Republic, Austria, Hungary and Slovakia to the fungicides triadimenol, tebuconazole, propiconazole, flutriafol and fenpropimorph. The highest resistance value was shown to triadimenol, which attained a mean resistance factor (MRF) of 29 (expressing how many times the population is more resistant than are standard sensitive isolates) in the mildew population from the Czech Republic. The mildew populations from eastern Slovakia and eastern Hungary, populations geographically isolated from the other populations, showed very high sensitivity to all fungicides tested. There was most sensitivity to fenpropimorph (smallest MRF values) compared with the other fungicides. Cross-resistance was established among all triazoles used, but not between triazoles and fenpropimorph. Sensitivity of wheat powdery mildew populations from Central Europe to these fungicides is considered adequate, and the development of resistance has shown a decreasing tendency in recent years.     

我国西南稻区白背飞虱,褐稻虱的迁飞和发生特点

由于西南稻区的地理位置、地势、地形、气候和水稻种植制度等因素的影响,白背飞虱和褐稻虱的迁飞和发生情况与我国东部稻区相比较,有其不同的特点: 迁飞特点有:贵州东南部迁入期较早,全区迁入虫量大,白背飞虱为春季迁入的优势种;云南境内,从南向北地势逐步抬升,迁入期和主要为害时期亦逐渐推迟,虫种由褐稻虱较多而变成白背飞虱为优势虫种;四川盆地迁入始期和主要迁入期由东向西推进;主害代的迁入虫源路径多;夏季短、中距离的迁飞频繁,有的年分在中稻上常造成两次主害时期等。发生特点有:常年三省的东、南部地区发生程度重,三省的西、北部地区发生程度轻;近期迁入虫量是中稻或晚稻上主害代的主要虫源;虫量相应集中,加重为害程度;另方面天敌种类多,数量较大,对飞虱种群数量有一定的抑制作用。上述迁飞和发生特点可作为拟定西南稻区对两种稻飞虱预测预报和防治策略的理论依据。     

How can research on pathogen population biology suggest disease management strategies? The example of barley scald (Rhynchosporium commune)

Barley scald fungus, Rhynchosporium commune, belongs to a host‐specialized species complex infecting grasses. Coalescent analyses of several genes indicate that R. commune originated c. 2500 years ago, after the domestication of barley. Phylogeographical analyses identified a diversity hotspot in Scandinavia, indicating an origin in northern Europe. After its emergence, R. commune became distributed globally on infected seeds, eventually invading the Fertile Crescent and infecting wild barley progenitors. Analyses of gene flow identified historical routes of migration out of Scandinavia and indicate a high degree of modern gene flow among South Africa, Australia and New Zealand. About 76% of global species diversity is found within barley fields, with all field populations showing a genetic structure consistent with sexual recombination. High levels of regional gene flow suggest wind‐dispersed ascospores and movement of infected seed. Quantitative traits, including pathogen aggressiveness, thermal sensitivity and fungicide resistance, showed high heritability and high levels of diversity within nine globally representative populations. Field experiments provided evidence for a fitness cost associated with complex virulence and a trade‐off between pathogenic and saprophytic fitness. All findings indicate that global R. commune populations have significant potential to evolve rapidly in response to environmental changes, including deployment of resistant cultivars, fungicide applications and global warming. Specific recommendations to improve management of barley scald include: (i) focus resistance breeding efforts in northern Europe, which offers the best location to screen germplasm and may provide useful sources of scald resistance; (ii) improve seed treatment, certification and quarantine programmes to limit long distance pathogen movement; (iii) manage barley stubble to decrease pathogen population size, limit production of sexual inoculum and reduce the pathogen's evolutionary potential.     

Common vole (Microtus arvalis) ecology and management: implications for risk assessment of plant protection products

Common voles (Microtus arvalis) are common small mammals in some European landscapes. They can be a major rodent pest in European agriculture and they are also a representative generic focal small herbivorous mammal species used in risk assessment for plant protection products. In this paper, common vole population dynamics, habitat and food preferences, pest potential and use of the common vole as a model small wild mammal species in the risk assessment process are reviewed. Common voles are a component of agroecosystems in many parts of Europe, inhabiting agricultural areas (secondary habitats) when the carrying capacity of primary grassland habitats is exceeded. Colonisation of secondary habitats occurs during multiannual outbreaks, when population sizes can exceed 1000 individuals ha^?1. In such cases, in‐crop common vole population control management has been practised to avoid significant crop damage. The species' status as a crop pest, high fecundity, resilience to disturbance and intermittent colonisation of crop habitats are important characteristics that should be reflected in risk assessment. Based on the information provided in the scientific literature, it seems justified to modify elements of the current risk assessment scheme for plant protection products, including the use of realistic food intake rates, reduced assessment factors or the use of alternativee focal rodent species in particular European regions. Some of these adjustments are already being applied in some EU member states. Therefore, it seems reasonable consistently to apply such pragmatic and realistic approaches in risk assessments for plant protection products across the EU. © 2013 Society of Chemical Industry     

Genetic diversity of Dothistroma septosporum in Estonia, Finland and Czech Republic

Dothistroma needle blight is one of the most damaging foliage diseases in pine plantations worldwide. Recently it has become more aggressive in native pine stands in northern America and has been found frequently on Scots pine stands in northern Europe. In Estonia and Finland it was noticed for the first time in 2006 and 2008, respectively and in Central Europe in the late 1990s. We show considerable diversity in allele patterns of several microsatellite loci in populations of these countries which does not support the hypothesis of a recent introduction. We investigated 104 isolates by using eight microsatellite loci. Estonian and Finnish isolates originated from P. sylvestris and those from the Czech Republic from six species of Pinus spp. and Pseudotsuga menziesii. The genetic diversity was considerable in all three populations, and did not differ significantly between populations. The results suggest slight migration from south to north, even if no similar haplotypes were found between any of the populations. Both, the pairwise genetic differentiation and Nei’s genetic distance reflected geographic distances between the populations. Differentiation between the studied populations of D. septosporum was low but statistically significant. Only 6 % of the genetic variation was due to differences between populations. The high haplotypic diversity, low number of identical haplotypes, and low degree of genetic disequilibrium in all investigated populations suggested occurrence of sexual proliferation in this area, although the sexual state of the fungus has not been recorded in Estonia and Finland. The high diversity may suggest a long presence of D. septosporum in northern Europe, or alternatively, its recent introduction as a massive inoculum from an unknown direction.     

Potential distribution ranges in Europe for Ips hauseri, Ips subelongatus and Scolytus morawitzi, a CLIMEX analysis

Introduced bark and ambrosia beetles have become a worldwide problem for the forest industry as well as for recreational parks and nature reserves by directly damaging wood material and killing trees or by vectoring lethal tree diseases. In this study we used the climatic modeling program CLIMEX to simulate potential distribution ranges for three different Asian bark beetles, Ips hauseri (Reitter), Ips subelongatus (Motschulsky) and Scolytus morawitzi (Semenov) on the basis of their current distribution. The program calculates an ecoclimatic index based on the life cycle requirements of a species and thus represents the probability of a viable population existing at a certain location. Simulations show that all of the studied species have a potential distribution according to climatic factors. Also, potential hosts for these species grow in much of Europe, making the potential establishment of these species possible. Simulation with the Intergovernmental Panel on Climate Change (IPCC) climate change scenario A1B resulted in changes of 200 to 900 km at the northern and southern edges of the distribution ranges for the studied species.     

Plum pox situation in Europe

The EPPO Conference on plum pox organized at Bordeaux (FR) in 1993–10 included a round-table session at which scientists from research and plant protection services of EPPO Member Governments reviewed the current national status of the disease. These reports have been summarized and compared here. They show that plum pox is the most serious disease of stone fruit in Europe and that nearly all countries which produce stone fruits are affected to a greater or lesser extent. Broadly, Europe can be divided into three zones: (1) the central and eastern countries in which plum pox spread relatively early and levels are generally high; (2) the northern and western countries in which plum pox levels are very heterogeneous (sometimes fairly widespread as in Germany, sometimes very restricted as in France, sometimes absent as in Netherlands); (3) Mediterranean countries in which spread is relatively recent and there is high risk of further spread.     

Prognose von Wühlmaussch?den in Forstkulturen

Zusammenfassung  In den Jahren 1980–1990 wurden auf insgesamt 100 Probefl?chen Wühlmausf?nge für die Schadensprognose in Forstkulturen durchgeführt. Die gefangenen Tiere wurden im Labor eingehender untersucht und verschiedene Parameter mit der Dichteentwicklung der Schadnager verglichen. Für einen beschr?nkten Zeitraum von etwa 3 Monaten war die ?u?erlich me?bare L?nge der m?nnlichen Gonaden mit der Populationsentwicklung korreliert. Bei einer mittleren L?nge der Testes über 3,5 mm wurde eine Zunahme der Populationsdichte beobachtet (Gradation). Bei einer geringeren Gonadenl?nge war die Populations-entwicklung rückl?ufig (Retrogradation). Dieser Zusammenhang kann für eine Schadensprognose bedeutsam sein.

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Predicting damages of voles in forest cultivations

Voles like the Field VoleMicrotus agrestis, the Common VoleM. arvalis, the Bank VoleClethrionomys glareolus and the Water VoleArvicola terrestris can cause severe damages in forest cultivations by gnawing the trunks and the roots of the young trees. Damages occur during winter time when the population density of these species is high and food resources are limited. The forecast of the development of vole populations is needed to prepare countermeasures against vole damages. The increase or decrease of a vole population can be predicted, if the fertility of the caught specimens is observed. The gonadal size of the males was a suitable predictor for the trend of the development of a vole population. The change of population density of the Bank Vole in a time interval of 3 month (September–December) was highly correlated (r=0.86) with the gonadal index of males. The percentage of pregnant or lactating femals was also a good indicator, but less suitable for practical use. It is assumed, that the hormones of the hypophysis like FSH, LH and Prolactin rule the growth of the gonads, the fertility and the reproduction in a vole population. Testis size is an indicator for the activity of these fertility hormones and for the reproductive process. It can be used to predict the development of vole populations for a limited time interval.

     

基于MaxEnt模型预测叉角厉蝽在全球的潜在地理分布

为明确草地贪夜蛾Spodoptera frugiperda的捕食性天敌——叉角厉蝽Eocanthecona furcellata在全球的潜在地理分布,基于叉角厉蝽在全球已有的历史分布记录,结合环境数据,采用MaxEnt生态位模型结合GIS技术对其在全球范围的适生区进行分析。结果显示,最暖季降水和最冷季平均温度是影响叉角厉蝽分布的主要环境因素。预测的叉角厉蝽在各个洲均可能发生,适生区集中分布在亚洲东部、东南亚大部、印度半岛东部、非洲南部东西沿海岸地区、南美洲中部地区及澳洲北部沿海岸地区。表明叉角厉蝽适生性较强,可以充分利用其捕食性释放到田间用于生物防治。     

Phytophthora acerina sp. nov., a new species causing bleeding cankers and dieback of Acer pseudoplatanus trees in planted forests in northern Italy

A severe dieback of Acer pseudoplatanus trees was noticed in planted forest stands in northern Italy in 2010. Affected trees showed collar rot and aerial bleeding cankers along the stems, leading to crown dieback and eventually death. An unknown Phytophthora species was consistently isolated from necrotic bark and xylem tissue and from rhizosphere soil. Based on its unique combination of morphological and physiological characters and phylogenetic analysis, this new taxon is here described as Phytophthora acerina sp. nov. Phylogenetic analysis of ITS, cox1 and β‐tubulin gene regions demonstrated that P. acerina is unique and forms a separate cluster within the ‘P. citricola complex’, closely related to P. plurivora. Phytophthora acerina is homothallic with smooth‐walled oogonia, thick‐walled, mostly aplerotic oospores with a high abortion rate, paragynous antheridia, and persistent, morphologically variable semipapillate sporangia. Four to 5‐week‐old cultures produced globose to subglobose, appressoria‐like and coralloid hyphal swellings and characteristic stromata‐like hyphal aggregations. Optimum and maximum temperatures for growth are 25°C and 32°C, respectively. Genetic uniformity of all 15 studied isolates and the apparent absence of this species in the extensive surveys of nurseries, forests and seminatural ecosystems conducted in the previous two decades across Europe indicate a recent clonal introduction to northern Italy. Under‐bark inoculation tests demonstrated high aggressiveness of P. acerina to A. pseudoplatanus indicating that this pathogen might be a serious risk to maple plantations and forests in Europe.