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The egg parasitoid Gryon aetherium Talamas (Hymenoptera: Scelionidae) is a promising candidate for biocontrol of Bagrada hilaris Burmeister (Hemiptera: Pentatomidae) in the Southwestern USA. Bagrada hilaris is a worldwide invasive pest of crops in the family Brassicaceae. The present study aims to evaluate the parasitoid's host range in a European context. These tests complement studies underway in California and provide risk information for a potential release of G. aetherium in southern continental Europe where B. hilaris is likely to spread in the future. Of the 11 nontarget species tested, four pentatomids were in the physiological host range of G. aetherium: Carpocoris mediterraneus, Dolycoris baccarum, Graphosoma italicum and Ancyrosoma leucogrammes. Parasitism rates on these four species were lower in choice than in no-choice conditions. Surprisingly, the three Eurydema spp. that belong to the same tribe as B. hilaris (Strachiini) and feed on plants in the family Brassicaceae were not parasitized. No parasitism was observed on the cosmopolitan invasive pentatomids Nezara viridula and Halyomorpha halys, nor on the rhopalid Liorhyssus hyalinus. Parasitoids that developed from non-target species were larger than ones developing on B. hilaris and took more time to complete development. [ABSTRACT FROM AUTHOR]

Simple Summary: The greatest challenge for modern agriculture is the management of the damage caused by insect pests, in alternative to chemical insecticides, which are the most widely used tools for controlling these pest species. Among the sustainable alternatives to chemical insecticides, the Sterile Insect Technique (SIT) can help to control the target population through the release of adults that have been rendered sterile via irradiation in the field. In order to evaluate the applicability of this technique, a great deal of knowledge about the biology of the target species is required. In this study, we investigated the mechanism of sperm competition in a polyandrous stink bug species, Bagrada hilaris. In view of the possible application of the SIT, it is important that irradiated males have the same potential to compete with wild non-irradiated ones, even at the post-copulation stage. The results obtained showed a mechanism of sperm mixing. The stink bug, Bagrada hilaris, is a pest of mainly Brassicaceae crops. It is native to Africa and Asia and was recently reported as invasive in the southwestern part of the USA and in South America. There are no mitigation programs in place that do not involve pesticides. Therefore, much attention has recently been paid to the study of this species in order to identify sustainable and effective control strategies, such as the Sterile Insect Technique (SIT). In order to evaluate the suitability of the SIT on this pest, the mechanism of post-copulatory sperm competition was investigated. This is a polyandrous species, and it is thus important to understand whether irradiated males are able to compete with wild, e.g., non-irradiated, males for sperm competition after matings. Sperm competition was studied by sequentially mating a healthy virgin female first with a non-irradiated male, and then with a γ-irradiated (Co-60) one, and again in the opposite order. Males were irradiated at three different doses: 60, 80, and 100 Gy. The fecundity and fertility of the females, in the two orders of mating, were scored in order to perform an initial assessment of the success of sperm competition with a P2 index. Sperm from the non-irradiated male were utilized at the lowest irradiation doses (60 and 80 Gy), whereas the irradiated sperm were preferentially utilized at the highest dose (100 Gy). Bagrada hilaris exhibited high variability in P2 indexes, indicating a sperm-mixing mechanism. [ABSTRACT FROM AUTHOR]

Invasive alien plant species (IAPs) are causing significant negative impacts on agricultural production, threatened native species and ecosystems, the services they provide and public health thereby affecting European biodiversity and its economy. IAPs invade all types of natural and managed habitat and their impacts, through increased numbers and area invaded, are growing exponentially. Current control options in Europe are largely limited to manual and chemical control, which is high cost, short‐term in effectiveness and with regards to chemical control declining in public acceptability. Globally, classical biological control (CBC) is widely and successfully used to manage many IAPs. CBC aims to redress the ecological imbalance caused by the IAPs, generally being released without their natural enemies. The steps are to select, risk assess potential specific natural enemy biocontrol agents of the IAP (from the IAP's native range) and follow regulatory approval prior to releasing them to ecologically suppress their abundance. CBC is not widely used in Europe. Only five active programmes exist. In this paper, we apply an existing framework to develop a ranked list of environmental IAPs named in the EU Regulation on Invasive Species for biocontrol. We used a scoring system based on existing knowledge on the IAPs impacts, the amount of effort needed to deliver a CBC programme targeting them and the feasibility and likelihood of success of such programmes. We identify 16 IAPs in Europe for which CBC has relatively high potential and discuss existing knowledge that can underpin any future investments in such activities against each of these IAPs. The top three species being Pontederia crassipes, Pistia startiotes and Acacia saligna. This research should support decision‐making on the instigation of future CBC programmes against environmental IAPs in Europe. We set this analysis in the context of other operational and regulatory constraints on developing CBC programmes against environmental IAPs in Europe. [ABSTRACT FROM AUTHOR]

The USA has been actively involved in classical biological control projects against invasive insect pests and weeds since 1888. Classical (importation) biological control relies upon natural enemies associated through coevolution with their target species at their geographic origin to also provide long-term, self-sustaining management where the pest/weed has become invasive. Biological control agents are a form of genetic resources and fall under the purview of the 1993 Convention on Biological Diversity (CBD) and its Nagoya Protocol (NP), which entered into force in 2014 to address equitable sharing of benefits arising from utilization of genetic resources. Safe and effective classical biological control agents have historically been shared among countries experiencing problems with invasive species. However, a feature of the Nagoya Protocol is that countries are expected to develop processes governing access to their genetic resources to ensure that the benefits are shared equitably—a concept referred to as "access and benefit sharing" (ABS). Although the USA is not party to the CBD nor the NP, US biological control programs are affected by these international agreements. Surveying, collecting, exporting and importing of natural enemies may be covered by new ABS regulatory processes. Challenges of ABS have arisen as various countries enact new regulations (or not) governing access to genetic resources, and the processes for gaining access and sharing the benefits from these resources have become increasingly complex. In the absence of an overarching national US policy, individual government agencies and institutions follow their own internal procedures. Biological control practitioners in the USA have been encouraged in recent years to observe best practices developed by the biological community for insect and weed biological control. [ABSTRACT FROM AUTHOR]

These parasitoid species have been detected in Pakistan using sentinel eggs, an extremely valid biocontrol tactic based on exposing a consistent number of eggs of the target pest species for an amount of time suitable to obtain the egg parasitoid oviposition [[17]]. The overall effect of dose and cross types on the number of eclosed eggs, the number of oviposited eggs, and the proportion of eggs hatched per female are reported. [Extracted from the article]

The phytophagous stinkbug pest Bagrada hilaris (Hemiptera: Pentatomidae) (= bagrada) buries single eggs in the ground, an exception among pentatomids. To investigate potential biological control strategies to mitigate the pest’s damages, an evaluation of the egg parasitoid Gryon gonikopalense (Hymenoptera: Scelionidae) as a biocontrol agent is ongoing. Its ability to detect and parasitize buried bagrada eggs could be a key factor in the short and long-term regulation of bagrada populations in the U.S. However, this foraging ability would be relevant only if bagrada mainly oviposits in the soil and if G. gonikopalense mainly parasitizes buried eggs, which is currently unknown. We assessed the oviposition pattern of bagrada in presence of three host plants (broccoli, white mustard and white rocket) and at three density levels (one, five or fifteen copulae). The prevalent oviposition site of bagrada was in the soil (92% of eggs) with no effect from the host plant neither the bagrada density. Eggs oviposited on mustard were mainly present on the top third, but no distribution pattern was observed on broccoli and white rocket. Gryon gonikopalense preferred parasitizing buried eggs (87% of total parasitism). It was also able to parasitize non-buried eggs whatever their location. Artificially increasing the number of non-buried eggs in the experimental design only resulted in a slight reduction in the parasitism of buried eggs (70%). As a result, this study highlights the relevance of using G. gonikopalense against bagrada as its specific foraging behaviour responds well to the main oviposition behaviour of its host. [ABSTRACT FROM AUTHOR]

Host detection and parasitism by egg parasitoids involve host chemical recognition, spatial overlapping, and the ability to overcome physical barriers. Within the context of importation biological control, we examined the potential of Gryon gonikopalense (Hym.: Scelionidae), against the stinkbug pest, Bagrada hilaris (Hem.: Pentatomidae). Bagrada is invasive in the Americas where it negatively impacts cruciferous cropping systems. Within Pentatomidae, bagrada possesses a unique behavioral trait in that its eggs are oviposited buried. Our study aimed to evaluate the capacity of G. gonikopalense to respond to bagrada ovipositional behavior. We showed that G. gonikopalense exhibits a well-adapted foraging behavior observed by tracking and successfully parasitizing 2 mm-deep buried bagrada eggs, which was further supported by video recordings. Four conditions of egg detectability by parasitoids (free eggs, naturally buried eggs, and manually buried with disturbed or clean sand) and foraging durations were tested in Petri dishes. The parasitism rate of 100% was obtained after 72hours for both free and naturally buried eggs; a rate of 71% was obtained after 2 h with free eggs. There was no significant difference concerning the parasitoid success rate (< 40%) with manually buried eggs. Our data suggested that host egg detection was based on chemical cues since parasitism success was reduced by up to 20% when eggs were manually buried under a clean substrate or a substrate previously used for oviposition but disturbed. Gryon gonikopalense can overcome both the egg detection and physical barrier constituted by the sand to parasitize the pest despite a reduced number of progeny produced. [ABSTRACT FROM AUTHOR]

Plant invasions are rarely homogenous. Processes such as selection, drift, gene flow, and founding events can rapidly shape the genetic diversity and spatial population structure of an invasion. We investigated the diversity, origins and population structure of Verbascum thapsus (common mullein), an introduced plant in North America. Despite this species being facultatively outcrossing, we found the invasion dominated by a single genotype (61% of plants were identical amplified fragment length polymorphism [AFLP] genotypes in the western USA). Fifty percent of the invasion populations were monotypic, and we found 32 genotypes overall in the 431 plants sampled from the invasion. In contrast, populations were much more diverse in the native Eurasian range, with 394 genotypes found in 479 plants. Further, we found an exact genetic match between the common genotype 1 in the USA and plants from Belgium and Germany. The identification of the most common and diverse invasive genotypes of common mullein allows their use in tests of management tools and further studies of mechanisms of this invasion. [ABSTRACT FROM AUTHOR]

Invasive stink bugs (Hemiptera: Pentatomidae) are responsible for high economic losses to agriculture on a global scale. The most important species, dating from recent to old invasions, include Bagrada hilaris (Burmeister), Halyomorpha halys (Stål), Piezodorus guildinii (Westwood), Nezara viridula (L.), and Murgantia histrionica (Hahn). Bagrada hilaris, H. halys, and N. viridula are now almost globally distributed. Biological control of these pests faces a complex set of challenges that must be addressed to maintain pest populations below the economic injury level. Several case studies of classical and conservation biological control of invasive stink bugs are reported here. The most common parasitoids in their geographical area of origin are egg parasitoids (Hymenoptera: Scelionidae, Encyrtidae, and Eupelmidae). Additionally, native parasitoids of adult stink bugs (Diptera: Tachinidae) have in some cases adapted to the novel hosts in the invaded area and native predators are known to prey on the various instars. Improving the efficacy of biocontrol agents is possible through conservation biological control techniques and exploitation of their chemical ecology. Moreover, integration of biological control with other techniques, such as behavioural manipulation of adult stink bugs and plant resistance, may be a sustainable pest control method within organic farming and integrated pest management programs. However, additional field studies are needed to verify the efficacy of these novel methods and transfer them from research to application. [ABSTRACT FROM AUTHOR]

Molecular markers prove to be an invaluable tool in assessing the introduction dynamics, pattern of range expansion, and population genetics of an invasive species. Ventenata dubia (Leers) Coss. (Aveneae; ventenata) is a diploid, primarily self-pollinating, annual grass native to Eurasia and Northern Africa. The grass has a detailed herbarium collection history in the western United States since its discovery in eastern Washington in 1952. Genetic analysis of 51 invasive populations (1636 individuals) of V. dubia, coupled with historical records, suggests moderate propagule pressure from multiple introductions, followed by local or regional range expansion. Allozyme analysis detected nine multilocus genotypes (MLGs) across eight western US states. A single MLG, referred to as the most common genotype, was detected in 37 of 51 (72.5%) invasive populations across all states. The other eight MLGs were generally found in fewer populations, with limited geographic distributions. Despite multiple introductions, invasive populations exhibit low levels of genetic admixture, low levels of genetic diversity within populations (A = 1.03, %P = 2.94, Hexp = 0.007) and high genetic differentiation among populations (GST= 0.864). The apparent reduced evolutionary potential of most V. dubia populations did not preclude the initial establishment and rapid spread of this species across its new range in the western US. [ABSTRACT FROM AUTHOR]

In weed biocontrol, there is a need for pre-release efficacy assessments for potential agents. Genista monspessulana ((L.) L. A. S. Johnson (Fabaceae), French broom) is an invasive perennial shrub in the western U.S. The galling weevil Lepidapion argentatum Gerstaecker is a potential biocontrol agent. The impact of increasing weevil density on galling damage, plant height, width, leaf damage, and relative growth rate (RGR) was assessed in greenhouse experiments on two to three-month-old seedlings infested with either one or three weevils. Infestation by three female weevils caused 48% more galls producing 27% more larvae than did infestation with one female while causing only 1% leaf damage and no difference in total leaf area. Infestation with multiple weevils caused a 55% and 29% decrease in plant height and canopy width respectively, while single-weevil infestation decreased height by 32% and width to the same degree as for multiple weevils. The RGR of seedlings infested with three weevils was three times slower than the controls, while growth was reduced 2-fold by single-weevil infestation. Reductions in plant size and growth rate induced by weevil galling could reduce plant competitive survival to reproduction and also plant population dispersal as seedlings. Our results suggest that L. argentatum has the potential to cause impact to French broom seedlings if released in the invasive range. [ABSTRACT FROM AUTHOR]

Biological control of weeds is a globally recognised approach to the management of some of the most troublesome invasive plants in the world. Accidental introductions of agents accounted for all weed biological control agent establishments in the European Union until 2010, but these examples include some current or emerging control successes both large and small, from the redistribution of the weevil Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae) for the control of small outbreaks of Azolla filiculoides Lam. (Azollaceae), to the large scale control provided by the cochineal insect Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae), used against some problematic prickly pears (Opuntia spp. (Cactaceae)), and the ragweed beetle Ophraella communa LeSage (Coleoptera: Chrysomelidae), against common ragweed, Ambrosia artemisiifolia L. (Asteraceae), which are providing benefits to an increasing number of Member States of the European Union. Recent programmes involving the intentional introduction of biological control agents against target weeds including Fallopia japonica (Hout.) Ronse Decr. (Polygonaceae), Impatiens glandulifera Royle (Balsaminaceae) and Acacia longifolia (Andrews) Willd (Fabaceae) show a shift from luck to judgement in the European Union. The inclusion of new weed targets on the European Invasive Species Regulation should lead to a growth in the profile and use of biological control which would be assisted by the publication of any successes from the few intentional introductions covered in this paper. [ABSTRACT FROM AUTHOR]

Determining the most likely source of an invasive pest species might help to improve their management by establishing efficient quarantine measures and heading the search of efficient biological control agents. Planococcus ficus is an invasive mealybug pest of vineyards in Argentina, California, Mexico, Peru and South Africa. This mealybug pest had a previously known geographic distribution spanning southern Europe, the Middle East, and parts of northern Africa. In North America, Pl. ficus was first discovered in the early 1990s and soon thereafter in Mexico. To determine the origin of invasive populations in North America, Pl. ficus from California and Mexico were compared with material throughout its presumptive native range in the Mediterranean region, as well as material collected from an older invasion in South Africa and recently invaded Argentina. From each sample location, genomic DNA was sequenced for the nuclear internal transcribed spacer one (ITS1) and the mitochondrial cytochrome c. oxidase one (CO1). Phylogenetic analyses of CO1, ITS1 and concatenated CO1 and ITS1 data-sets using Bayesian and neighbor-joining analysis support two major divisions: a European grouping (Europe, Tunisia, Turkey) and a Middle Eastern grouping (Israel and Egypt). The invasive populations in Argentina and South Africa align with the European group and the invasive populations in North America align with the Middle Eastern group, with one Israel sample aligning closely with the North American clade, suggesting that Israel was the origin of those populations. [ABSTRACT FROM AUTHOR]

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Investigating the origins of invasive populations provides insight into the evolutionary and anthropogenic factors underlying invasions, and can inform management decisions. Invasive species introduced for horticultural purposes often have complex origins typified by multiple introductions of species, cultivars, and genotypes, and interspecific and intraspecific hybridizations in introduced ranges. Such complex introduction histories may result in complex genetic signatures in the invaded range, making inferences about origins difficult, particularly when all putative sources cannot be sampled. In this study, we inferred the origins of the invasive French broom complex in California using 12 nuclear microsatellite markers. We characterized the genetic diversity and population structure of invasive and horticultural brooms in their invaded range in California and of Genista monspessulana in its native Mediterranean range. Overall, no significant differences in allelic richness, observed heterozygosity, inbreeding, or genetic structure were observed between the invaded and native ranges, but differences existed among populations within ranges. Bayesian STRUCTURE analysis revealed three genetic clusters in the French broom complex. Nearly all native G. monspessulana assigned highly to a single cluster. Many invasives assigned to a second cluster that contained Genista canariensis, Genista stenopetala, and ornamental sweet broom, and the remaining invasives assigned to a third cluster that also contained some G. monspessulana individuals from Sardinia and Corsica. Admixture between the second and third clusters was detected. Approximate Bayesian Computation analysis of six alternative scenarios supported the hypothesis that some invasive French broom is derived from an unsampled population branching from ornamental sweet broom. A combination of factors, including multiple introductions, escapes from cultivation, and inter-taxon hybridization, likely contribute to the invasive success of French broom in California and may have important implications for management, in particular biological control. [ABSTRACT FROM AUTHOR]

A systematic review focused by plant on non-target impacts from agents deliberately introduced for the biological control of weeds found significant non-target impacts to be rare. The magnitude of direct impact of 43 biocontrol agents on 140 non-target plants was retrospectively categorized using a risk management framework for ecological impacts of invasive species (minimal, minor, moderate, major, massive). The vast majority of agents introduced for classical biological control of weeds (>99% of 512 agents released) have had no known significant adverse effects on non-target plants thus far; major effects suppressing non-target plant populations could be expected to be detectable. Most direct non-target impacts on plants (91.6%) were categorized as minimal or minor in magnitude with no known adverse long-term impact on non-target plant populations, but a few cacti and thistles are affected at moderate (n = 3), major (n = 7) to massive (n = 1) scale. The largest direct impacts are from two agents (Cactoblastis cactorum on native cacti and Rhinocyllus conicus on native thistles), but these introductions would not be permitted today as more balanced attitudes exist to plant biodiversity, driven by both society and the scientific community. Our analysis shows (as far as is known), weed biological control agents have a biosafety track record of >99% of cases avoiding significant non-target impacts on plant populations. Some impacts could have been overlooked, but this seems unlikely to change the basic distribution of very limited adverse effects. Fewer non-target impacts can be expected in future because of improved science and incorporation of wider values. Failure to use biological control represents a significant opportunity cost from the certainty of ongoing adverse impacts from invasive weeds. It is recommended that a simple five-step scale be used to better communicate the risk of consequences from both action (classical biological control) and no action (ongoing impacts from invasive weeds). [ABSTRACT FROM AUTHOR]

Aim Canada thistle ( Cirsium arvense- Cardueae, Asteraceae) is one of the worst invasive plants world-wide. Native to Eurasia, its unintentional introduction into North America now threatens the native flora and is responsible for enormous agricultural losses. The goals of this study are to: (1) reconstruct the evolutionary history of C. arvense and estimate how often it may have colonized North America, (2) compare the genetic diversity between European and North American populations to detect signs of demographic bottlenecks and/or patterns of population admixture, and (3) conduct bioclimatic comparisons to infer eventual niche shifts following this species' introduction into North America. Location Europe and North America. Methods A total of 1522 individuals from 58 populations were investigated with six microsatellite markers. Estimates of heterozygosity ( HE) and allelic richness ( RS) were quantified for each population, and population structure was inferred via analyses of molecular variance (AMOVAs), principal components analyses (PCAs), Mantel tests and Bayesian clustering analyses. Climatic niche spaces were based on 19 bioclimatic variables extracted from approximately 32,000 locations covering the entire range, and compared using PCA and hierarchical cluster analysis. Results Although there is evidence of multiple introductions from divergent European lineages, North American populations of C. arvense exhibited significantly lower levels of genetic diversity than their putative ancestors. Bioclimatic comparisons pointed to a high degree of niche conservatism during invasion, but indicated that genotypes from the former USSR and Central European mountain chains were probably best adapted to invade North America upon entry into the continent. Main conclusions Genetic and historical data suggest that C. arvense first entered North America from Western Europe with the first European settlers, and was later introduced from Eastern Europe into the prairie states during the agricultural boom. The species went through a significant bottleneck following its introduction into the New World, but the level of genetic diversity remained high owing to admixture between genetically differentiated lineages and to a highly efficient outcrossing breeding system. [ABSTRACT FROM AUTHOR]

A simple molecular tool was developed and tested to identify seven mealybug species found in North American vineyards: Pseudococcus maritimus Ehrhorn, Pseudococcus viburni (Signoret), Pseudococcus longispinus (Targioni-Tozzeti), Pseudococcus calceolariae (Maskell), Planococcus ficus (Signoret), Planococcus citri (Risso), and Ferrisia gilli Gullan. The developed multiplex PCR is based on the mitochondrial cytochrome c oxidase subunit one gene. In tests, this single-step multiplex PCR correctly identified 95 of 95 mealybug samples, representing all seven species and collected from diverse geographic regions. To test the sensitivity, single specimen samples with different Pl. ficus developmental stages (egg to adult female and adult male) were processed PCR and the resulting output provided consistent positive identification. To test the utility of this protocol for adult males caught in sex baited pheromone traps, Pl. ficus adult males were placed in pheromone traps, aged at a constant temperature of 26 ± 2°C, and processed with the multiplex each day thereafter for 8 d. Results showed consistent positive identification for up to 6 d (range, 6-8 d). Results are discussed with respect to the usefulness of this molecular tool for the identification of mealybugs in pest management programs and biosecurity of invasive mealybugs. [ABSTRACT FROM AUTHOR]

The alien invasive vines Vincetoxicum rossicum and Vincetoxicum nigrum (swallow-wort) are of major concern in eastern North America, where both species invade forested landscapes and threaten faunal and plant diversity. Among the few native natural enemies reported in Eurasia, the specialist chrysomelid, Chrysochus ( Eumolpus) asclepiadeus (Coleoptera; Chrysomelidae), feeds on Vincetoxicum both above ground (as adults) and below ground (as larvae). The goal of our study was to assess the potential for using this beetle to manage invasive Vincetoxicum spp. in North America by quantifying the impact of herbivory by C. asclepiadeus on Vincetoxicum and determining whether this effect was influenced by plant density ('Allee effect'). Experimental work was carried out using a split plot design in the field in southern France. Pots of V. nigrum and V. hirundinaria, a substitute for V. rossicum, were planted at high (255 plants/m), medium (127 plants/m), and low (32 plants/m) plant densities, and received treatments of 0 (control), 2 or 4 C. asclepiadeus adult beetles/pot. Leaf damage, root and shoot biomass, and quantity of seeds were measured after 4 weeks of adult feeding. Densities of 2 and 4 beetles/pot caused similar damage, with significant reductions in plant biomass at low plant density. While V. hirundinaria increased allocation of resources to roots in response to herbivory, V. nigrum did not. Seed production was greatest for both species grown at low plant densities, but only V. nigrum produced fewer seeds in response to herbivory. Our results, based on the effects of herbivory by C. asclepiadeus adults, suggest that if this beetle were to be introduced into North America for the management of Vincetoxicum spp. such as V. rossicum, reductions in plant biomass and spread would be greatest if beetles were released on edges or in newly-established satellite populations at low plant densities. In the case of V. nigrum, beetles could be released irrespective of plant density as reproductive output and seed dispersal would be reduced similarly. [ABSTRACT FROM AUTHOR]

Knowing the origin of invasive taxa, whether multiple introductions have occurred, and levels of genetic variation relative to the native range, is vital to conducting rigorous tests of hypotheses to explain biological invasions. We explore phylogeographical relationships of two Eurasian knapweed taxa that are invasive in North America, Centaurea diffusa and C. stoebe micranthos (Asteraceae), using chloroplast DNA intron sequences. We also gathered data from C. stoebe stoebe, hybrids between C. diffusa and C. stoebe stoebe ( C. x psammogena), and three other species in the genus. We sequenced 213 individuals from Eurasia and North America, and found 22 haplotypes. Centaurea diffusa has lower haplotype diversity and allelic richness in the introduced range relative to the native range. Even with reduced variation, the data suggest at least two introductions of C. diffusa. There is a trend towards reduced variation in C. stoebe micranthos, but it is not significant. One of the haplotypes found in North American C. stoebe micranthos matches a haplotype from a taxon other than C. stoebe micranthos in Europe. This suggests introgression of the chloroplast between taxa, or possibly the invasion of another Centaurea taxon into North America. Additionally, C. diffusa, C. stoebe micranthos, and C. stoebe stoebe share several haplotypes, including their most common haplotype. This suggests ongoing hybridization between the species or incomplete segregation. These data can guide further exploration for the origins of these species, and point out locations within the introduced range with unique and diverse genetic makeup. [ABSTRACT FROM AUTHOR]

The annual grass Taeniatherum caput-medusae (L.) Nevski (medusahead) is highly invasive on rangelands of the western United States. It originates from the Mediterranean basin and was introduced accidentally into North America in the late 1800s. To increase our knowledge of the soil factors that may contribute to its invasiveness, we conducted a reciprocal transplant experiment. Seed sources used were from an invasive population in northeastern California, USA and from a native population in southern France. Four soils were used: two from northeastern California, invaded (USI) and non-invaded (USN) by T. caput-medusae; two from southern France, with T. caput-medusae occupied (FR+) and a similar soil presently unoccupied (FR−) by T. caput-medusae. Treatments were control and autoclaved. Seeds were sown in containers (six replicates) for each soil and treatment combination of the reciprocal planting matrix and allowed to grow for 60 days. Following harvest, above-ground and below-ground tissue was dried and weight recorded separately. Above-ground tissue was analyzed for nutrient concentrations and various soil nutrient pools were quantified. Above-ground mass of T. caput-medusae was greatest in the USN soil and least in the FR- soil. Growth was affected by significant seed source × soil and treatment × soil interactions. French seed produced larger plants than did US seed when grown in the USN soil. For the USI soil, plant growth was significantly greater in the autoclaved soil than control. Availability of soil Fe, Mn, and ortho-P were significant predictors of plant growth as shown by stepwise regression. Moreover, the positive effect on growth of T. caput-medusae, due to autoclaving of USI soil, may be partially a consequence of elevated nutrient availability. Our data also suggests that US seed may have evolved a greater ability to uptake Mn from soil than French seed. Elevated soil nutrient availability in our western United States study area is a potential factor explaining the invasiveness of T. caput-medusae. [ABSTRACT FROM AUTHOR]

Simple Summary: French broom is a leguminous shrub that is an internationally significant invasive alien weed in California and nearby US states that competes with native vegetation and increases the risk of wildfires. French broom originates from the Mediterranean region and is the target for classical biological control. Exploration for prospective biological control agents in the native region of Western Europe resulted in the collection of the weevil Lepidapion argentatum. We conducted preliminary field studies showing that this weevil can impact seed production in the native habitat. We also measured the specificity of this candidate biocontrol agent in laboratory conditions on 36 plant species growing in California and Australia. Our data showed that, in no-choice tests, seven species were directly negatively impacted by gall formation induced on plant stems by the weevil, but at different levels, including two lupine species commonly distributed in California. Further experiments are needed to ascertain the safety of this candidate biocontrol agent prior to release. French broom (Genista monspessulana) (Fabaceae) is a perennial species native to the Mediterranean basin. Introduced in the 19th century as an ornamental plant, it is currently invasive in California and Australia. The current research is focused on biocontrol with the use of the phytophagous weevil Lepidapion argentatum (Brentidae). Its capacity to develop both in the stem galls and pods of French broom makes it a promising candidate. The impact on the reproduction of French broom was studied in Southern France and revealed that it could effectively reduce the number of viable seeds by 18.8%, but also increased the number of aborted seeds by 10% within the attacked pods. To evaluate the specificity of L. argentatum, choice and no-choice tests were performed in 2012 and 2015 on a total of 36 non-target closely related species. Results revealed the presence of galls and larvae in the stems of seven species, including two endemic Californian lupines; i.e., Lupinus arboreus blue and Lupinus chamissonis. In the future, new tests will be conducted to determine if L. argentatum is able to complete its entire development lifecycle on the non-target species where galls have previously been observed. [ABSTRACT FROM AUTHOR]

Simple Summary: Tree of heaven is a tree native from Asia, considered a serious weed where ever it occurs outside of its native range. Among the herbivores which attack it is a tiny mite, Aculus mosoniensis, which causes serious malformations of the growing tips. In order to determine whether this species is safe to use as a biological control agent in Europe, where the mite has already been recorded, and elsewhere within the invasive range of tree of heaven, host range testing is required. After testing several tree species related to tree of heaven, it was found that this mite was unable to reproduce on any other species except tree of heaven, and importantly there was no damage or sign of feeding on any of the test species. Thus we conclude that this is a safe biological control agent and will help to control this highly invasive tree. Tree of heaven (Ailanthus altissima) is a fast-growing deciduous tree native to China, considered a serious invasive species worldwide, with several socio-economic and ecological impacts attributed to it. Chemical and mechanical methods have limited efficacy in its management, and biological controls may offer a suitable and sustainable option. Aculus mosoniensis (Ripka) is an eriophyid mite that has been recorded to attack tree of heaven in 13 European countries. This study aims to explore the host range of this mite by exposing 13 plant species, selected either for their phylogenetic and ecological similarity to the target weed or their economic importance. Shortly after inoculation with the mite, we recorded a quick decrease in mite number on all nontarget species and no sign of mite reproduction. Whereas, after just one month, the population of mites on tree of heaven numbered in the thousands, irrespective of the starting population, and included both adults and juveniles. Significantly, we observed evidence of damage due to the mite only on target plants. Due to the specificity, strong impact on the target, and the ability to increase its population to high levels in a relatively short amount of time, we find A. mosoniensis to be a very promising candidate for the biological control of tree of heaven. [ABSTRACT FROM AUTHOR]

Centaurea stoebe (subspecies C. s. stoebe and C. s. micranthos[S. G. Gmelin ex Gugler) Hayek] and Centaurea diffusa are Eurasian plant species that have invaded much of North America. We isolated seven microsatellite loci from C. stoebe and two loci from C. diffusa. All loci described here amplify in both species and have between six and 25 alleles each. These markers will be useful in examining population structure and addressing questions regarding these invasions. [ABSTRACT FROM AUTHOR]