Abstract  Establishment potential is one of the primary components of invasive species risk assessment. Models that predict establishment of potentially invasive ornamental crops often ignore differences among cultivars and the variability in plant response to site-specific factors. The objective of this study was to determine the extent to which differences among cultivars and habitat characteristics affect establishment of 5 cultivars of ornamental cleome. Experiments were conducted to compare germination, survival, and growth of cultivars in cultivated (gardens) and noncultivated (roadsides and prairies) environments and, in prairies, the effects of competition (low, intermediate, and high). In the first experiment, germination, survival, and growth were recorded in gardens, prairies, and roadsides in four locations in Minnesota. In the second experiment, the effects of competition with resident species were studied in five seed lots from three cultivars in three prairie sites. Additionally, a quantitative description of germination and transplantable seedling quality, when grown under greenhouse production standards, was obtained and compared with results from the cultivated and noncultivated outdoor environments. Germination in greenhouse conditions was significantly greater (78%) than in garden, prairies, or roadsides (< 46%). Mortality was greater in noncultivated than in cultivated environments (3% wk(-1) and 1.4% wk(-1), respectively). Survival was affected by competition, which reduced population establishment. Cultivar differences were most pronounced at seedling emergence, whereas habitat characteristics were more influential at later stages of the life cycle. Germination and plant height were similar among noncultivated environments. Variability in seedling emergence, survival, and growth in response to cultivar, habitat, and competition are important determinants of establishment potential. Among the cultivars studied, the native cleome, roughseed clammyweed, has a greater establishment potential than the nonnative cleome, spiderflower.

Abstract  Weeds pose severe threats to agricultural and natural landscapes worldwide. One major reason for the failure to effectively manage weeds at landscape scales is that current Best Management Practice guidelines, and research on how to improve such guidelines, focus too narrowly on property-level management decisions. Insufficiently considered are the aggregate effects of individual actions to determine landscape-scale outcomes, or whether there are collective practices that would improve weed management outcomes. Here, we frame landscape-scale weed management as a social dilemma, where trade-offs occur between individual and collective interests. We apply a transdisciplinary system approach-integrating the perspectives of ecologists, evolutionary biologists and agronomists into a social science theory of social dilemmas-to four landscape-scale weed management challenges: (i) achieving plant biosecurity, (ii) preventing weed seed contamination, (iii) maintaining herbicide susceptibility and (iv) sustainably using biological control. We describe how these four challenges exhibit characteristics of 'public good problems', wherein effective weed management requires the active contributions of multiple actors, while benefits are not restricted to these contributors. Adequate solutions to address these public good challenges often involve a subset of the eight design principles developed by Elinor Ostrom for 'common pool social dilemmas', together with design principles that reflect the public good nature of the problems. This paper is a call to action for scholars and practitioners to broaden our conceptualization and approaches to weed management problems. Such progress begins by evaluating the public good characteristics of specific weed management challenges and applying context-specific design principles to realize successful and sustainable weed management.

Abstract  There is increasing urgency to develop and deploy sustainable sources of energy to reduce our global dependency on finite, high-carbon fossil fuels. Lignocellulosic feedstocks, used in power and liquid fuel generation, are valuable sources of non-food plant biomass. They are cultivated with minimal inputs on marginal or degraded lands to prevent competition with arable agriculture and offer significant potential for sustainable intensification (the improvement of yield without the necessity for additional inputs) through advanced molecular breeding. This article explores progress made in next generation sequencing, advanced genotyping, association genetics, and genetic modification in second generation bioenergy production. Using poplar as an exemplar where most progress has been made, a suite of target traits is also identified giving insight into possible routes for crop improvement and deployment in the immediate future.

Abstract  Plant breeders have played an essential role in improving agricultural crops, and their efforts will be critical to meet the increasing demand for cellulosic bioenergy feedstocks. However, a major concern is the potential development of novel invasive species that result from breeders' efforts to improve agronomic traits in a crop. We use reed canarygrass as a case study to evaluate the potential of plant breeding to give rise to invasive species. Reed canarygrass has been improved by breeders for use as a forage crop, but it is unclear whether breeding efforts have given rise to more vigorous populations of the species. We evaluated cultivars, European wild, and North American invader populations in upland and wetland environments to identify differences in vigor between the groups of populations. While cultivars were among the most vigorous populations in an agricultural environment (upland soils with nitrogen addition), there were no differences in above- or below-ground production between any populations in wetland environments. These results suggest that breeding has only marginally increased vigor in upland environments and that these gains are not maintained in wetland environments. Breeding focuses on selection for improvements of a specific target population of environments, and stability across a wide range of environments has proved elusive for even the most intensively bred crops. We conclude that breeding efforts are not responsible for wetland invasion by reed canarygrass and offer guidelines that will help reduce the possibility of breeding programs releasing cultivars that will become invasive.

Abstract  In response to agricultural concerns, US legislatures in the late 19th and early 20th centuries enacted laws to regulate invasive plant species whose presence negatively affected crop yields. More recently, these laws regulating noxious weeds have expanded their focus to protect the environment and ecosystem functions. Concurrently, federal mandates have incentivized the commercialization of high-yielding and, in some cases, potentially invasive bioenergy feedstocks. This chapter considers the invasion potential of novel bioenergy crops within the context of conflicting regulatory provisions designed to prevent invasion and promote development of novel feedstocks. The fragmented nature of environmental regulations across multiple jurisdictions (local, state, national) necessitates increased attention by stakeholders to ensure cultivation of bioenergy crops do not result in a largescale invasion. To mitigate such an eventuality, it is recommended that pre-market invasion risk assessments and post-introduction negligence liability actions be codified into new and revised bioenergy laws at all levels of government.

Abstract  BACKGROUND: Accurate pesticide use data are essential when studying the environmental and public health impacts of pesticide use. Since the mid-1990s, significant changes have occurred in when and how glyphosate herbicides are applied, and there has been a dramatic increase in the total volume applied.

METHODS: Data on glyphosate applications were collected from multiple sources and integrated into a dataset spanning agricultural, non-agricultural, and total glyphosate use from 1974-2014 in the United States, and from 1994-2014 globally.

RESULTS: Since 1974 in the U.S., over 1.6 billion kilograms of glyphosate active ingredient have been applied, or 19 % of estimated global use of glyphosate (8.6 billion kilograms). Globally, glyphosate use has risen almost 15-fold since so-called "Roundup Ready," genetically engineered glyphosate-tolerant crops were introduced in 1996. Two-thirds of the total volume of glyphosate applied in the U.S. from 1974 to 2014 has been sprayed in just the last 10 years. The corresponding share globally is 72 %. In 2014, farmers sprayed enough glyphosate to apply ~1.0 kg/ha (0.8 pound/acre) on every hectare of U.S.-cultivated cropland and nearly 0.53 kg/ha (0.47 pounds/acre) on all cropland worldwide.

CONCLUSIONS: Genetically engineered herbicide-tolerant crops now account for about 56 % of global glyphosate use. In the U.S., no pesticide has come remotely close to such intensive and widespread use. This is likely the case globally, but published global pesticide use data are sparse. Glyphosate will likely remain the most widely applied pesticide worldwide for years to come, and interest will grow in quantifying ecological and human health impacts. Accurate, accessible time-series data on glyphosate use will accelerate research progress.

Abstract  Many species prioritized for bioenergy crop development possess traits associated with invasiveness, necessitating a priori efforts by ecologists to identify species or cultivars with minimal invasive potential. The grass Miscanthusxgiganteus Greef et Deu ex Hodkinson et Renvoize is a candidate for biomass production in the northern US maize belt, with both sterile and fertile varieties commercially available in the near future. Prior to widespread deployment, the invasive potential of both varieties must be quantified. Using M.xgiganteus demographic and seed dispersal data, we parameterized an age-/stage-structured integrodifference equation model to estimate potential spread rates of sterile and fertile M.xgiganteus. We identified thresholds for reproductive parameters, above which population numbers and space occupied are likely to increase. Our simulations considered lateral spread of M.xgiganteus but not dispersal of rhizome fragments. When clonal recruitment is absent, population growth rate for sterile M.xgiganteus is projected to be slightly <1 (=0 center dot 979), indicating gradual population decline over the long term. A sterile M.xgiganteus population may increase in numbers and space under certain conditions: annually rhizome sprouting must be >20% and rhizome production must be 1 per plant. The relatively slow spread rates (00 center dot 09myear1) estimated for sterile M.xgiganteus would not apply in scenarios where rhizomes were dispersed long distance. For a fertile M.xgiganteus genotype, even low rates of seed viability and survival, seedling survival and seed germination support rapidly expanding populations. Synthesis and applications. Spatial demographic models offer a powerful tool for quantifying risk of invasive spread by bioenergy crops. Our results suggest that sterile and fertile cultivars of M.xgiganteus have markedly different invasive potential and therefore should be considered separately in management and policy decisions. Feral populations of sterile M.xgiganteus would need to experience frequent and severe disturbance to pose a significant invasion risk, indicating that they should be grown well away from riparian areas prone to streambank scouring. In contrast, cultivars of M.xgiganteus bearing fertile seed may be very difficult, if not impossible, to contain.

Abstract  Bamboo species have been promoted for utility in both biomass and pulp production because of their high productivity. However, some bamboo species are known to be problematic invaders. Our goal was to use a weed risk assessment (WRA) tool to evaluate and compare invasion risk of non-native running and clumping bamboo species, many of which are under consideration as paper pulp and bioenergy crops in the continental United States. WRAs were conducted for 18 running and 29 clumping bamboo species using a version of the Australian WRA modified for the U.S. We tested for differences in scores and the number of questions answered for clumping and running species, the relationship between the WRA score and the number of questions answered, and the questions that differentiated low and high-risk species. Overall, we found that running bamboo species present a significantly higher invasion risk than clumping species. Only one running bamboo species (Chimonobambusa tumidissinoda) was identified as low risk and one clumping species (Bambusa bambos) was high risk for invasion. History of invasiveness elsewhere, the ability to form dense thickets, and unintentional dispersal of viable rhizome pieces were associated with significantly greater predicted risk. Commercial applications of bamboo should focus on the use of low invasion risk clumping bamboo species to reduce the risk of escape and colonization of nearby natural areas. Further, bamboo-specific best management practices (BMPs) should be implemented to reduce the probability of invasion for species used in commercial production.

Abstract  Elephantgrass (Pennisetum purpureum Schum.) has demonstrated potential for use as a biomass crop, but in Florida, some naturalized types are invasive weeds in sugarcane (Saccharum sp.) fields, along roadsides, and in natural areas. It is not known whether elephantgrass introductions and breeding lines developed for biomass production (i.e., "selected"clones) differ from naturalized populations sufficiently that risk assessment and regulatory decisions should be made at the level of the clone instead of the species. The objective was to compare morphological and physiological traits of elephantgrass-naturalized populations and selected clones. Ten naturalized populations and six selected clones were evaluated in replicated trials at two field locations during 2 years. Selected clones were 8-14 % taller and had leaf blade length that was 48-87 % longer, and leaf blade width that was 61-89 % wider than naturalized clones. Selected types averaged 5.7 to 7.2 fewer tillers per plant than naturalized types, but tiller mass of selected types was 70 % greater than naturalized types. Leaf N concentration was 43 % greater for selected types and was associated with greater light-saturated leaf photosynthesis, stomatal conductance, leaf transpiration rate, and leaf dark respiration than naturalized types. Photosynthetic parameters indicated a greater maximum photosynthetic rate, leaf dark respiration, and light compensation point for selected versus naturalized clones. Clones selected for use as biomass crops differ widely in morphology and physiological response from naturalized populations, supporting a conclusion that risk assessment of elephantgrass should occur at the level of the clone rather than the species.

Abstract  Biofuel crops are being selected to require minimal inputs, tolerate marginal growing conditions, and exhibit rapid growth rates—agronomically desirable traits that also characterize many of our worst invasive species. Many of the candidate biofuel crops are known invasive or noxious species in portions of their non-native range. Most invasive species were intentionally introduced and cause tremendous environmental and economic harm globally. Necessary elements for the sustainable production of bioenergy include assessment and subsequent mitigation of the invasive potential of biofuel crops prior to large-scale adoption, as the economic benefits of bio-based energy may be offset by environmental damage and management costs. We outline a proposed invasiveness risk evaluation to be conducted on each crop, and subsequent mitigating practices along each step of the biofuel pathway.

Abstract  Many invasive plants originate as cultivated species. The growing demand for renewable energy has stimulated agricultural production of native and non-native perennial grasses, but little is known about their potential to become invasive outside cultivation, particularly at the early establishment phase. We evaluated effects of propagule pressure and establishment limitations for early establishment of four potential bioenergy grasses in agricultural field margins and forest understory across a 6.3 degrees latitudinal gradient (Ontario, Canada; Illinois and Virginia, USA). We used multiple seed introductions in different years and followed their fate for up to three growing seasons. High interannual variability in establishment indicates that the frequency of propagule introduction is important for invasion outside cultivation. Establishment limitations were stronger in forest than fieldmargins; of 328,800 seeds added, only 1 of 505 persisting seedlings occurred in forest. Removal of competing vegetation had small and variable effects on establishment among sites and species. Unlike previous short-term experiments, our results indicate the potential for the persistence of these bioenergy grasses in both vegetation and seed bank, and highlight the importance of long-term experiments in evaluating invasion risk.

Abstract  Resistance to insecticides and herbicides has cost billions of U.S. dollars in the agricultural sector and could result in millions of lives lost to insect-vectored diseases. We mostly continue to use pesticides as if resistance is a temporary issue that will be addressed by commercialization of new pesticides with novel modes of action. However, current evidence suggests that insect and weed evolution may outstrip our ability to replace outmoded chemicals and other control mechanisms. To avoid this outcome, we must address the mix of ecological, genetic, economic, and sociopolitical factors that prevent implementation of sustainable pest management practices. We offer an ambitious proposition.