Weed In Europe Research Articles

Growth performance of Vallisneria spiralis under oligotrophic conditions supports its potential invasiveness in mid‐elevation freshwaters

SummaryUnder the influence of human‐driven impacts, inland aquatic habitats of intermediate to mid‐high elevations may provide new areas for the establishment of lowland macrophytes that usually act as opportunistic species. Vallisneria spiralis, an obligate lowland macrophyte with an altitudinal range not exceeding 300 m, is a typical component of the plant diversity in meso‐ to eutrophic water habitats. This species is an engineering species in ecosystems, being able to modify the colonised sediments promoting its self‐maintenance under eutrophic conditions. Vallisneria spiralis delivers large amounts of oxygen to roots promoting the loss of nitrogen via denitrification and reducing the internal nutrient load of colonised environments. However, the establishment of the species results in rapid sediment accumulation and the progressive loss of more sensitive macrophytes. Furthermore, V. spiralis is one of the most widespread alien aquatic weeds in Europe. In this study, we evaluated the growth performance of V. spiralis under oligotrophic conditions at the upper limit of its altitudinal distribution using two different techniques: harvesting and leaf‐marking. Vallisneria spiralis proved to be able to grow under oligotrophic conditions, even if at rates lower than those recorded under eutrophic conditions. Accordingly, V. spiralis represents a potential threat for oligotrophic aquatic habitats at moderate elevations. However, the high variability observed in the growth responses highlights the need of further investigation to evaluate the key factors involved in the establishment and survival of the species.

Comparing existing weeds and commonly used insectary plants as floral resources for a parasitoid

The potential consequences of deploying weed and non-weed floral resources in a three trophic-level system were evaluated in the laboratory. Four flowering plants were used: the two common weeds shepherd’s purse Capsella bursa-pastoris (globally widespread) and white rocket Diplotaxis erucoides (a common weed in Europe) and two common flowering plants: buckwheat Fagopyrum esculentum and alyssum Lobularia maritima. Adults of the aphid parasitoid Diaeretiella rapae were exposed to flowering buckwheat and survived 4–5 times longer than those in the control (water only) and 2–3 times longer than when provided with flowering alyssum, or the other two species. All plant species significantly increased parasitoid longevity, egg load and achieved fecundity compared with the control, with buckwheat having the greatest effect. This work illustrates that the functional diversity of ‘weeds’, if appropriately managed, has potential to enhance biological control efficacy without the need for agronomic and other challenges which are involved in adding specific non-crop flowering plants such as buckwheat to agroecosystems. In the field, factors such as the plants’ phenology, agronomy and competitiveness with the crop will need to be evaluated before they can be truly ranked.

Combining a weed traits database with a population dynamics model predicts shifts in weed communities.

A functional approach to predicting shifts in weed floras in response to management or environmental change requires the combination of data on weed traits with analytical frameworks that capture the filtering effect of selection pressures on traits. A weed traits database (WTDB) was designed, populated and analysed, initially using data for 19 common European weeds, to begin to consolidate trait data in a single repository. The initial choice of traits was driven by the requirements of empirical models of weed population dynamics to identify correlations between traits and model parameters. These relationships were used to build a generic model, operating at the level of functional traits, to simulate the impact of increasing herbicide and fertiliser use on virtual weeds along gradients of seed weight and maximum height. The model generated ‘fitness contours’ (defined as population growth rates) within this trait space in different scenarios, onto which two sets of weed species, defined as common or declining in the UK, were mapped. The effect of increasing inputs on the weed flora was successfully simulated; 77% of common species were predicted to have stable or increasing populations under high fertiliser and herbicide use, in contrast with only 29% of the species that have declined. Future development of the WTDB will aim to increase the number of species covered, incorporate a wider range of traits and analyse intraspecific variability under contrasting management and environments.

The invasive aquatic plant Ludwigia grandiflora affects pollinator visitants to a native plant at high abundances

The presence of an invasive species can either have a negative effect on pollination of natives by competing for pollinators or a positive effect since they may act as ‘magnet’ species facilitating pollinator visits to co-flowering species. We studied the plant-pollinator interactions for Ludwigia grandiflora, a highly invasive aquatic weed in Europe. First, a food web approach was used in one field site and our results showed an integration of L. grandiflora into the native plant-pollinator network with a dominance of L. grandiflora in terms of frequency of pollinator visits. Second, an experiment was designed to identify the pollinator guild of invasive L. grandiflora and native Lythrum salicaria and to measure interspecific pollinator switching. We also estimated the pollinator-mediated effect of high relative abundance of L. grandiflora (% cover of L. grandiflora) on L. salicaria plants. We monitored species composition, abundance and foraging behaviour of pollinators on L. salicaria. In addition, we assessed seed set per fruit of L. salicaria. Competition for pollinator services between invasive L. grandiflora and native L. salicaria seems minor as there was no evidence for decreased pollinator visitation or seed set of L. salicaria. On the contrary, more pollinators were recorded on L. salicaria plants when the cover of L. grandiflora was high compared to the control plants thereby indicating a facilitation effect, however this was not reflected in seed set. Despite the fact that L. grandiflora is well integrated in the native plant-pollinator network and highly attractive to pollinators, there was no evidence of negative impact of L. grandiflora on pollination of a native plant.

A process-based approach to predicting the effect of climate change on the distribution of an invasive allergenic plant in Europe.

Ambrosia artemisiifolia is an invasive weed in Europe with highly allergenic pollen. Populations are currently well established and cause significant health problems in the French Rhône valley, Austria, Hungary and Croatia but transient or casual introduced populations are also found in more Northern and Eastern European countries. A process-based model of weed growth, competition and population dynamics was used to predict the future potential for range expansion of A.artemisiifolia under climate change scenarios. The model predicted a northward shift in the available climatic niche for populations to establish and persist, creating a risk of increased health problems in countries including the UK and Denmark. This was accompanied by an increase in relative pollen production at the northern edge of its range. The southern European limit for A.artemisiifolia was not expected to change; populations continued to be limited by drought stress in Spain and Southern Italy. The process-based approach to modelling the impact of climate change on plant populations has the advantage over correlative species distribution models of being able to capture interactions of climate, land use and plant competition at the local scale. However, for this potential to be fully realised, additional empirical data are required on competitive dynamics of A.artemisiifolia in different crops and ruderal plant communities and its capacity to adapt to local conditions.

Management of roadside populations of invasive Ambrosia artemisiifolia by mowing

SummaryAmbrosia artemisiifolia (common ragweed) is a highly allergenic alien weed in Europe, which spreads rapidly along roadsides. Road verges are subject to frequent mowing, which further increases the spreading of the plants' seeds. Ambrosia artemisiifolia reacts to cutting by producing new shoots, which are able to develop flowers and ultimately new seeds. An effective mowing regime that would decrease the production of seeds and their dispersal is desirable to control the spread of the plant, but an appropriate way of mowing has yet to be found. In this study, we explored how the reproductive traits of A. artemisiifolia plants in seven spontaneous roadside populations reacted to the application of different mowing regimes over 3 years. The mowing regimes that were applied differed in the timing and frequency of cuttings. We found that the cutting regime, if appropriately timed, can strongly influence the production of male inflorescences (i.e. allergenic pollen), of female flowers (i.e. seeds) and had an impact on the phenological development of the plant. Based on our findings, we suggest that the optimal management of the plant along roadsides must be adjusted to its phenological development. The most effective mowing method of control consists of a first cut shortly before male flowering, to limit the quantities of released pollen, followed by subsequent cuts before the onset of new flowers on the resprouting lateral shoots.

Effects of the seed weight and burial depth on the seed behavior of common ragweed (Ambrosia artemisiifolia)

Common ragweed (Ambrosia artemisiifolia L.) is one of the annual plants that were described recently as invasive weeds in Europe. This species is described as an invasive plant that produces seeds that are highly variable. Its production of variably sized seeds is regarded as promoting its spread in different environments. Experiments were carried out to determine the influence of the seed weight and temperature on germination and the influence of the seed weight and burial depth on seedling emergence. The seeds were divided into a number of classes of weight and the seed weight effect on germination was evaluated by Petri dish assays. In another experiment, the seeds were buried at different depths in a clay soil/sand mix to estimate the burial effect on germination and seedling emergence. The germination level of A. artemisiifolia was high overall, between 76.8% and 94.2%. The seed germination was modified by temperature but it was not influenced by the seed weight. The amounts of germination and seedling emergence were greater for the seeds on the soil surface and decreased with an increasing burial depth, from 2 to 8 cm. No germination or emergence was observed for the seeds that were buried at 10 and 12 cm. The lightest seeds were more sensitive to burial. A greater level of seedling emergence for those seeds that were placed near the soil surface could explain the success of this species in open habitats, where the probability of deeper burial is low. After high seed production, the management of A. artemisiifolia in fields could be partly achieved through soil tillage, burying seeds below 10 cm, and not carrying out deep soil tillage the following year.

POST Herbicide Combinations for Velvetleaf (Abutilon theophrasti) Control in Sugarbeet

Velvetleaf is one of the most significant and fastest spreading alien weeds in Europe, and it is a difficult weed to control in conventional sugarbeet. Laboratory experiments were carried out in 2007 and 2008 and field experiments were carried out in 2006, 2007, and 2008 with the aim of finding effective herbicide combinations and optimum timing of control. Herbicides containing the active ingredients phenmedipham, desmedipham, ethofumesate, clopyralid, and triflusulfuron were all tested at different timings. Phenmedipham + desmedipham + ethofumesate gave 87% velvetleaf control in pot experiments when applied at the growth stages of velvetleaf cotyledons and one true leaf, but only 27 to 42% control in field trials. Triflusulfuron gave 76% control in pot experiments and 83 to 88% control in field experiments. The timing of the first and second herbicide applications was very important: the first application of herbicides must be at the cotyledon stage of velvetleaf. A 1-wk delay in first application reduced herbicide efficacy by 8%. A 5-d period between the first and second treatments gave 93% control, while a 10-d period between the first and second treatments gave only 77% control. Sugarbeet yield decreased by 60 to 86% due to competition with velvetleaf when a standard herbicide combination (phenmedipham + desmedipham + ethofumesate) was used, and the velvetleaf produced between 6,700 and 14,800 seeds m−2. Inclusion of triflusulfuron in the herbicide treatment significantly reduced velvetleaf seed production to between 200 and 4,700 seeds m−2. In most cases, inclusion of triflusulfuron increased sugarbeet yield. Better velvetleaf control occurred in years when the sugarbeet canopy developed early and the index of leaf area of sugarbeet was higher.

Impact of climate and land use type on the distribution of Finnish casual arable weeds in Europe

Hyvönen T, Glemnitz M, Radics L & Hoffmann J (2011). Impact of climate and land use type on the distribution of Finnish casual arable weeds in Europe. Weed Research51, 201–208.SummaryThe aim of the study was to explore the impact of climate and land use type on species richness and abundance of arable weeds found as casual aliens in Finland. We used an empirical data set collected along a European climate gradient, from which 163 plants were selected for the analyses. Using generalised linear modelling (GLMM) and redundancy analysis (RDA), we compared species richness and abundance of all species and three functional groups (dicotyledons and grasses, C3 and C4 species, alien and native species to Europe), as well as occurrence of the 13 most common individual species between three land use types (fallow, low‐input and conventionally cultivated) and six regions. In general, fallowing and low‐input cultivation, as well as warmer climate, supported greater weed species richness and abundance. Temperature was found to be a more important factor for weed abundance than land use. The only exception was C4 species richness, which did not respond to either factor. The impact of land use was independent of climate for all variables, except C4 species abundance. Non‐cultivated fallows had more weeds than cultivated fields, in most cases. No difference was found in the species richness and abundance of grasses or in the occurrence of individual species between low‐input and conventionally cultivated fields. It was evident that climate and land use affect the distribution of arable weed species currently found as casual aliens in Finland. This suggests that climate warming will increase the risk of the population establishment of new weed species in northern regions.

Nipping aquatic plant invasions in the bud: weed risk assessment and the trade

The importation and sale of ornamental pond and aquarium plants is the most important pathway for the introduction of potential aquatic weeds into and subsequent spread of these within a country. Most current aquatic weeds were at one time deliberately imported for ornamental use. This article discusses a weed risk assessment approach to evaluating new potential weeds. It assesses the potential invasiveness of an aquatic plant based on its habitat versatility, competitive ability, reproductive output and dispersal mechanisms, range of potential impacts, potential distribution and resistance to management activities. The Aquatic Weed Risk Assessment Model (AWRAM) has been used to evaluate potential aquatic weeds in New Zealand, Australia and the USA. A similar approach could be used to guide the management of aquatic weeds in Europe. Banning the importation of highly ranked species effectively keeps biosecurity risks off-shore. Assessment of aquatic plant trade patterns, especially volumes of high-risk species, along with knowledge of current and potential distribution of those species and ease of management, are all factors to be considered when evaluating candidate plants for prevention of sale and distribution. This is a highly effective way of restricting both long-distance dispersal and density of propagules. A cooperative approach involving researchers, policy and trade representatives has been an effective way to achieve regulation of this risk pathway. European initiatives to prevent the distribution of potential aquatic weeds include the preparation of lists of known invasive aquatic species by the European and Mediterranean Plant Protection Organization (EPPO), with recommendations to member countries to consider measures to prevent their spread (e.g. banning importation of, banning sale and distribution of, and undertaking control programmes against those species). Belgian initiatives include an upcoming Royal Decree concerning the importation, exportation and possession of non-native invasive species, development of codes of conduct with the horticultural sector and prohibiting the sale, purchase and intentional release of these species in the wild. This article reviews these approaches and discusses other species of concern.

A. John, An enthusiasm for orchids: sex and deception in plant evolution

Spring arrives in western Australia by the end of August and the shrubby vegetation is colorful and richly perfumed. Some native orchids, though, are brownish or dull-maroon in color, the human nose fails to pick up any fragrance. The strange shapes of the flowers give them such common names as warty hammers (Drakaea), flying ducks (Paracaleana), lazy spiders (Caladenia) and elbow orchids (Arthrochilus). While we smell nothing, these orchids release odors irresistible to many species of wasps. The winged males mistake sculptures and patterns on the lip petals for the bodies of virginal and wingless females. As a lovesick insect backs out of the flower, a plug of sticky pollen globs is deposited on his back. If the same wasp visits a second flower of the same species then cross-pollination occurs and seeds are fertilized although the deceived insect fathers no offspring during this process. More than 40 orchid species found in Western Australia fool male wasps. Why is pollination-by-deceit such a common ‘‘theme’’ in this part of the world? Why not ask Professor John Alcock of Arizona State University? He is known for his research in insect behavior and some past work took him to the southwestern corner of Australia. If you have read his past books such as In a Desert Garden and The Kookburra’s Song you know he can turn the study of evolution into an entertaining and enriching trip. The book is beautifully illustrated with close up photos of the deceptive flowers ‘‘at work.’’ Yes, you will see wasps humiliated by plants within one of the world’s most exciting hotspots of biodiversity. For any serious environmentalist, the chapter on conservation is disturbing. Past agricultural practices in western Australia have reduced available sites where rare species once flourished. They have also introduced European weeds, contributed to a saltier water table and spread an epidemic of cinnamon fungus (Phytophora), killing native species in its path. However, the greatest pleasure in Dr. Alcock’s book is his ability to relate his personal orchid rambles to the work of Charles Darwin. Many of us forget that Darwin turned to orchid pollination following the publication of his Origin of Species. He used orchids as ‘‘model systems,’ in two editions of a book he first wrote in 1862, so the general reader could understand how flower organs fused together and evolved adaptations to better exploit the insects that visit them and transfer their pollen. Consequently, Alcock’s book is most convincing as a study on the survival of the reproductively fit. There’s a nice, early chapter on how and why plants move (also indebted to some of Darwin’s studies on carnivorous and Cassia plants). This is particularly useful for readers, as some Australian orchids have jointed and cantilevered lip petals that flip and reposition male wasps before they have the opportunity to recognize the floral fraud. Let me emphasize, though, that this is not a pretty little adventure in nature appreciation. You will be asked to think early and often and this means reading slowly and thoughtfully. Alcock is one feisty author. He wrestles with the papers of Stephen J. Gould and Richard Lewontin that downplayed the role of adaptation in evolution. For his next trick, Alcock takes a healthy crack at the Creationist movement for still insisting that orchids are beautiful examples of plants created by a sudden act of ‘‘intelligent design.’’ Curiously, Alcock’s book convinced me that both reputable scientists, like Gould and Lewontin, presented arguments as flawed as the stuff published by the people who currently hide under the banner of Creationism. The simple, take-home message from this American in Australia is that, if you ignore the results of almost 160 years of published research and do not bother to P. Bernhardt (&) Department of Biology, St. Louis University, St. Louis, MO 63103, USA e-mail: bernhap2@slu.edu

New hosts of Potato virus Y (PVY) among common wild plants in Europe

The infection capacity of Potato virus Y (PVY, genus Potyvirus) for wild-living plants, commonly occurring as arable weeds in Europe and native to or naturalised in other continents, was evaluated. In total, 3,712 and 802 seedlings representing 21 weed species were aphid and sap-inoculated with PVY, respectively. Experimentally-inoculated plants of Erodium cicutarium, Geranium pusillum, Lactuca serriola and Lamium purpureum tested positive by ELISA, but they did not display any disease symptoms. The presence of PVY in selected plants of the four species was confirmed by back-inoculations to Nicotiana tabacum and by immunocapture-reverse transcription-PCR performed on samples taken from weed and/or tobacco plants. Natural PVY infection in plants of the four wild species collected in the potato-growing area was detected by ELISA and confirmed by back-inoculations to tobacco plants. This study is believed to be the first report of PVY infection in E. cicutarium, G. pusillum and L. purpureum. Moreover, our findings reveal for the first time PVY infection in L. serriola in central Europe.

Wirksamkeit von Allergoiden zur subkutanen Applikation – Evidenzbewertung anhand klinischer Studien

Background: Allergoids are chemically modified allergens for specific immunotherapy. The clinical efficacy of commercially available allergoid products is hardly comparable to nonmodified allergens, because of their differing manufacturing methods, allergen compositions, therapy schemes and modifications, To ensure an evidence-based therapy, clinical efficacy of each allergoid should be proven by adequate clinical trials. Objective: To evaluate the clinical efficacy of available allergoid products in Germany for subcutaneous specific immunotherapy on the basis of the recommendations for clinical trials of the World Allergy Organization (WAO). Methods: A systematic literature search was conducted and the clinical efficacy was analysed according to the recommendations of the WAO. Results: 6 of 9 double-blind, placebo-controlled (DBPC) studies were included in the analysis. All trials were conducted with adults. A parallel literature search of German publications resulted in 2 DBPC studies. Clinical efficacy was documented for grass pollen allergoids in 3 studies with 3 products, and for mite allergoids in 2 studies with I product. Additionally, a German publication proved clinical efficacy in a DBPC study with a tree-allergoid preparation. There were no DBPC studies found for allergoid products with central European weeds. Moreover, studies showing long-term effects, prevention, carryover effects and studies in children were missing. Conclusion: Evidence of clinical efficacy, analysed according to the recommendations for clinical trials of the WAO, is limited to a few allergoid products and allergens.

Plant biology and other issues that relate to the management of water hyacinth: a global perspective with focus on Europe1

Water hyacinth reproduces vegetatively and sexually and seeds are numerous and long‐lived. Rates of vegetative growth are high (weight and numbers can double in less than 1 week in optimal conditions) and governed by temperature and available nutrients. The period from germination to setting seed can be less than 12 weeks. Dispersal of propagules is by flow, man and machines. Biomass of living material is high 90 to > 800 tonnes/ha and comprises around 95% water, and the weed often grows in inaccessible areas. Consequently, social, economic and environmental impacts of water hyacinth are often large and management of the problem becomes very important. However, management of water hyacinth is difficult, and utilization of this weed should not be mistaken as a control measure. Containment and eradication from a catchment may only be accomplished if the invasion is very young, small, isolated and accessible, and if the short‐term resource commitment is high. Most infestations are non‐eradicable because once noticed reaction time is too long. However, in Europe, as the weed invades new areas on the edges of its ecological range, eradication of new infestations could (should) be attempted as this is the most cost effective way to deal with the weed. In addition, pathway shut‐down and awareness campaigns should seek to reduce further new introductions, which, for spread to new regions, are mostly anthropogenic. For established populations the removal of accessible floating biomass can be accomplished using herbicides (if permitted) and by mechanical means. Both are expensive because re‐growth ensures repeated action is necessary. Biological control is a useful tool in warmer climates, less so in cooler climates. It may be more useful in cooler areas if integrated with other management techniques. Additional biological control agents are being studied to improve and broaden the value of biological control. The lack of policies to permit the use of biological control for weeds in Europe limits the ability to manage this weed.

Does invasion involve alternation of germination requirements? A comparative study between native and introduced strains of an annual Brassicaceae, Cardamine hirsuta

AbstractCardamine hirsuta is a European annual weed that has been naturalized in Japan. Although the species is a widespread weed in Europe, its introduction to the Japanese Islands occurred recently. We hypothesized that the introduction of Cardamine hirsuta required adaptation that has delayed its spread in Japan. The aim of this study is to determine whether there is a difference in temperature requirements for seed germination between Japanese and European strains of Cardamine hirsuta. We compared temperature requirements for seed germination, because it is known to be a critical determinant of phenology and thus is expected to be important in the success of introduction into different climates. Seeds of six and five strains from Japan and Europe, respectively, were used in seed germination experiments under five different temperature regimes. Japanese strains generally showed stronger initial seed dormancy and were characterized by suppressed germination in higher temperature regimes. European strains showed variable patterns of temperature‐dependent seed germination. It turned out that these temperature‐dependent dormancies are mediated by abscisic acid (ABA), because dormant seeds germinated under the presence of an inhibitor of ABA synthesis. Seed germination characteristics shared by Japanese strains presumably enhance long transport and autumn germination, while these characteristics are not necessarily common among European strains. The results are supportive for the idea that adaptation has altered germination characteristics of Cardamine hirsuta through the introduction process into Japan.

QUALITY OF CHAMOMILE TEAS - ESSENTIAL OIL CONTENT AND ITS COMPOSITION

Chamomile, a medicinal plant, with a history going back to the time of Egyptian pharaohs, is used in phytotherapy today and, unequivocally, will be used in the future. In the world market, the dry plant flowers, Chamomillae flos, are an important medicinal plant trade item. The annual consumption of chamomile flowers is several thousands of tons. GC analyses of the dry chamomile flowers of different origin, obtained from the commercially available teas, has demonstrated considerable variance in medically effective components. In addition, the constituents of chamomile essential oil differ from those of chamomile teas. Quality is important in the use of the flowers for tea production and for the pharmaceutical and cosmetic products, as shown by dissimilar pharmacodynamic effects. INTRODUCTION In the story of Peter Rabbit, a young rabbit named Peter develops a classic case of indigestion after eating his way through Mr. MacGregor's garden and barely surviving a frightening chase by the farmer before finding his way safely home. To cure the indigestion, his wise mother treats Peter with a cup of chamomile tea and puts him straight to bed. The chamomile tea referred to in this tale is brewed from the flowers of the chamomile (Matricaria recutita L.) plant (syn. camomile). This, the chamomile flower, was sacred to the ancient Egyptians and Romans and indeed, revered so much by the Egyptians that they consecrated the flower to their gods and dedicated the blossom to the Sun - the highest of all honors within their culture. Although generally considered a weed in Europe, the curative power was known historically used in traditional medicinal practices of various countries for many years. The popularity of chamomile grew throughout the Middle Ages, a time when people turned to chamomile as a remedy for numerous medicinal complaints, including nausea, nervousness, child ailments, skin diseases, and other similar afflictions. Recent and on- going research identifying specific anti-inflammatory, antibacterial, antiallergenic, and sedative properties of chamomile have validated the long held reputation of the plant and appear to be contributing to the popularity of this herb. Common on many family tables throughout Europe, chamomile tea offers a delicate flavor with a fruity aroma reminiscent of apples. Of course, the flavor of chamomile tea depends mainly upon elusive aromas of the flowers that are dependent on the characteristic quantity and composition of the essential oil. Today, most health stores, pharmacies and groceries offer a wide variety of chamomile teas produced by various tea companies. The raw chamomile used for processing of these teas originates from a number of different localities and sources (Salamon and Danielovic, 1998) and raises a question about the quality of the teas and remedies listed in the European Pharmacopoeia (Schilcher, 2005). The present research investigated qualitative-quantitative characteristics encountered in chamomile raw material used for herbal tea production and commonly sold in the market stores or chains in Slovakia.

Is Puccinia xanthii a suitable biological control agent of Ambrosia artemisiifolia?

Common ragweed, Ambrosia artemisiifolia, is a highly allergenic North American plant that has become invasive in some parts of Europe, Asia and Australia following its introduction to many places in the world. Some earlier works suggested that a microcyclic autoecious rust fungus, Puccinia xanthii, known to infect A. artemisiifolia in the USA only, can be considered as a potential classical biocontrol agent (BCA) of this noxious weed in Europe and elsewhere. However, an extensive field survey did not reveal the presence of either P. xanthii or any other rusts on common ragweed in 14 US states and two Canadian provinces in 2002 and 2003. Moreover, P. xanthii infecting A. artemisiifolia has never been recorded in Canada, although it is known to occur on A. trifida and Xanthium spp. there. Nevertheless, herbarium specimens collected between 1855 and 1963 in five states of the USA confirmed the presence of P. xanthii on A. artemisiifolia. It is concluded that currently P. xanthii cannot be regarded as a promising BCA of A. artemisiifolia, although it did occur on common ragweed at least a few decades ago in the USA and some forms of this rust species have already been evaluated as effective BCAs of Xanthium in Australia.

Managing Herbicide-resistant Blackgrass (Alopecurus Myosuroides): Theory and Practice

Blackgrass is the most important herbicide-resistant weed in Europe, occurring in 10 countries. Enhanced metabolism is the most common mechanism, conferring partial resistance to a wide range of herbicides, but acetyl-CoA carboxylase (ACCase) target-site resistance also occurs widely. Recently, acetolactate synthase (ALS) target-site resistance conferred by a Pro197 mutation was identified in blackgrass in England and is of concern because of increasing use of sulfonylurea herbicides such as mesosulfuron iodosulfuron. Resistance management strategies encourage (1) greater use of cultural control measures such as plowing, crop rotation, and delayed drilling; (2) reduced reliance on high-risk herbicides (ACCase, ALS); and (3) use of mixtures and sequences of herbicides with different modes of action. A key message is that, as weeds are relatively immobile, preventing and managing herbicide resistance is largely within the individual farmer's own control. In practice, financial and environmental pressures limit the scope for more cultural control, and the European Community Pesticide Review will result in fewer alternative herbicides being available. Consultants often feel unable to recommend lower risk but weaker herbicide strategies to farmers because the amount of blackgrass remaining might be unacceptable. This dilemma is exemplified by the recent introduction of a formulated mixture of mesosulfuron iodosulfuron, which has given outstanding control of blackgrass. Farmers expect new herbicides to become available, but this optimistic view appears misplaced. A primary aim is to continue to encourage farmers to integrate cultural and chemical control in a long-term strategy.Nomenclature: Iodosulfuron-methyl-sodium (proposed), [methyl 4-iodo-2-[3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-ureidosulfonyl]benzoate, sodium salt]; mesosulfuron-methyl (proposed), [methyl 2-[3-(4,6-dimethoxypyrimidin-2-yl)ureidosulfonyl]-4-methanesulfonamidomethylbenzoate]; blackgrass, Alopecurus myosuroides Huds. ALOMY.

The European Biological Control Laboratory: an existing infrastructure for biological control of weeds in Europe

The Agricultural Research Service of the United States Department of Agriculture has maintained a continuous European effort in classical biological control of exotic pests in the USA. The European Parasite Laboratory was established in France in 1919, while the European Weed Laboratory began operations in Rome in 1958. The two laboratories were merged in Montpellier in 1991 as the European Biological Control Laboratory (EBCL), becoming the primary overseas biocontrol laboratory of the USDA. The management of weeds, insect pests, and pathogens is an important feature of agricultural research programmes worldwide. These invasive species can lead to vast financial losses for countries engaged in agriculture. The overall goal of research at EBCL is to develop biological control technologies to be used to suppress invading weeds and insect pests. This is done through expeditions to find natural enemies (insects, mites and pathogens), or phytophagous, parasitoid or predator species. These are characterized in careful experimentation in quarantine facilities and eventually developed as biological control agents. Current weed projects include studies on the Centaurea spp., Arundo donax, Vincetoxicum spp., Isatis tinctoria, Taeniatherum sp. and Dipsacus sp. Insect projects research Lygus bugs, the olive fruit fly, the vine mealybug, and the Asian long‐horned beetle. The EBCL team is international and interdisciplinary. Entomology, plant and insect pathology, molecular biology and ecology are the main approaches of our biocontrol research. The team cooperates with universities and agencies worldwide.

Temperature and host-plant effects on development and population growth of Mecinus janthinus (Coleoptera: Curculionidae), a biological control agent for invasive Linaria spp.

Mecinus janthinus Germar is a European stem-mining weevil that has been established in North America as a biological control agent against the invasive European weeds Linaria vulgaris P. Mill. and Linaria dalmatica (L.) P. Mill. (Scrophulariaceae). Establishment success and impact of the weevil have varied widely among sites. We investigated the hypothesis that some of this variation may be due to a lack of sufficient time for M. janthinus to develop to the adult (overwintering) stage in less favorable climates. Development time of M. janthinus was measured in L. vulgaris and L. dalmatica at four constant temperatures, and logistic regression was used to derive a model for the effect of temperature on development. Development rates were simulated using historic climate data for a site in central Alberta (where establishment was marginal on L. vulgaris) and one in southern British Columbia (where outbreaks occurred, resulting in heavy damage to L. dalmatica). The model showed that, on average, the British Columbia site had 50 more days available for the weevil to lay eggs that could reach the adult stage in time for overwintering than did the Alberta site. This may explain the more rapid population buildup at the British Columbia site. This model could be used to predict the climatic suitability of other areas for establishment of M. janthinus. An unexplained result was the very low survival rate of eggs laid in L. dalmatica under the same experimental conditions.