Weeds In Agroecosystems Research Articles

A global perspective of education in weed science

AbstractIn modern agriculture, weed problems are predicted to worsen and become more complicated as a result of increasing invasiveness, herbicide resistance, and emphasis on high-input methods. Weeds cause huge economic yield losses that range from US$100 million to US$26 billion globally. The knowledge of weed science has offered success in the past through effective, reasonably priced, and secure technologies; specifically, synthetic herbicides to effectively control weeds in agroecosystems. Weed science is accepted and adopted by many universities with teaching, research, and/or extension programs in agriculture. Globally, approximately 7% of all the universities offering agricultural education have dedicated weed science departments focusing on weed biology, ecology, and management. Some universities also offer weed science degree programs or at least certain courses in their degrees related to associated disciplines, such as plant protection, agronomy, and ecology. Although substantial advances have been made in weed science, such as a separate weed science discipline, specialized journals, and specific weed science societies and conferences worldwide, many constraints (e.g., lack of trained weed scientists) and barriers to adoption of new weed science technologies remain. Slow modernization in weed science research and low funding has slowed the progress of this discipline. New curricula in the weed science discipline should focus on the role of biochemistry, evolutionary biology, molecular biology, and genetics in weed science research.

Inventory of Agrestals in Telangana, India: Their Impact and Management

Background: Understanding the sociological structure of weeds in crop fields is a pre-requisite for effective management. Identification and quantification of weed species found in different crops are possible to provide strategies for weed control. The exploration studies of weeds in agro-ecosystems are meager in Telangana, so that the present study has initiated to explore the weeds and educate the local farmers about the impact of agrestals and it will be of immense helpful to control the loss of crop productivity first of its kind in the region. Methods: The inventory of agrestals was carried out in 33 districts of Telangana State during 2016-2020 in two growing seasons (kharif, rabi) and it is an overview in agro-ecosystems. Result: The study focuses on the documentation of weed taxa in agricultural fields and recorded ca. 249 plant taxa pertaining to 150 genera and 47 families. Cyperaceae is the predominant family with 38 plant species followed by Poaceae (33 spp.), Asteraceae (20 spp.), Euphorbiaceae (17 spp.), Amaranthaceae (16 spp.). Echinochloa crus-galli is the dominant taxon in paddy crop with its mimic, where Cyperus rotundus is a serious competitor in many cultivated crops. The present study is very climacteric for farmers, agronomists and plant breeders for cognizance, to know the intensity of weeds impact and management skills.

The effects of wheat‐pea mixed intercropping on biocontrol potential of generalist predators in a long‐term experimental trial

AbstractArthropod generalist predators can be effective natural control agents of pests and weeds in agroecosystems. Their activity and contribution to biocontrol may increase in response to more complex agricultural habitats. In this study, we investigated the effects of winter wheat‐pea mixed intercropping on the biocontrol potential of generalist predators compared with the respective mono‐crops. We evaluated not only the effects during the intercropping season but also the pre‐crop values of the mixture for the subsequent barley crop. Furthermore, we evaluated the influence of different long‐term soil organic carbon and fertility management regimes on activity and biocontrol potential of predators. Field work was conducted over two seasons in a field experiment located in Gembloux, Belgium. A set of proxies for ecosystem functions were measured using the Rapid Ecosystem Function Assessment approach. We measured attack and predation rates of sentinel prey and weed seeds artificially placed in the field. Furthermore, we assessed activity density of the main groups of generalist predators during the exposure of the baits. Our results showed that crop type affected activity and biocontrol potential of predators. Predation rates were much lower in wheat than pea and wheat‐pea. The mixture wheat‐pea had a positive effect on predator activity density compared to wheat mono‐crop, while pea supported an intermediate activity of epigeal predators. In the second season of the field work, we found the highest biocontrol potential by predators in barley plots cultivated after pea. Finally, our results failed to find any differences in biocontrol potential of predators between long‐term soil organic carbon and fertilisation management strategies. These results suggest that crop type has a major relevance in influencing the activity of generalist predators, and the mixed intercropping wheat‐pea may represent a valid strategy to enhance biological pest control in comparison to wheat cultivated as mono‐crop. Furthermore, we show that the cultivation of pea as mono‐crop may have an important pre‐crop value within the rotation increasing the provision of ecosystem services such as biocontrol.

Mechanical weed management technology to manage inter- and intra-row weeds in agroecosystems - A review

Traditional manual weed management is one of the tedious and costly operations in the complete cycle of crop production, reasons being high labor costs, time and tedium. The herbicide use contributes to environmental pollution in addition to other disadvantages of concern. The increasing demand for toxicant free food has become a challenge for weed control. Hence, the mechanical weeding is gaining importance. Automation in agriculture has also improved the mechanization input in weed management. The rapid entry of sensors, microcontroller and computing technologies in the field has formed a foundation of agricultural autonomous guidance systems. An automated system is time effective for field operations, avoids huge labor requirement and health drudgery issues to provide an efficient farm operation. Generally manual tools such as khurpi (hand operated small hoe), grubber, spade, wheel hoe, push pull type of weeder are used by farmers for the removal of inter- and intra-row weeds with higher weeding efficiency in the range of 72 to 99% but field capacity is very low in the range of 0.001 to 0.033 ha/h. This review deliberates on the latest work being done on mechanical weed management such as tractor operated finger weeder, torsion weeder, ECO weeder, flame weeder, harrow and sensor-based technologies for management of inter- and intra-row weeds in crops with wider rows.

Mycorrhizal Symbioses Enhance Competitive Weed Growth in Biochar and Nutrient-Amended Soils

Velvetleaf (Abutilon theophrasti) is a highly competitive weed in agroecosystems that is well-studied for its efficient nitrogen (N) acquisition, yet research on its phosphorus (P) uptake is lacking. One pathway may be through symbioses with arbuscular mycorrhizal fungi (AMF) which increase nutrient acquisition. These AMF benefits can be further enhanced by soil amendment with biochar, although effects may vary with different biochar production characteristics. We implemented a fully factorial nutrient and biochar addition experiment in a greenhouse for six months to determine how AMF nutrient uptake impacts plant growth and how these effects vary between two biochar types. We measured total above- and belowground biomass, plant tissue concentration (N and P), AMF colonization and activity rates, and soil media N and P availability. Overall, we observed few statistically significant results, however AMF N uptake may have been more beneficial to velvetleaf than AMF P uptake as evidenced by increased biomass and tissue N concentrations in treatments where N was only accessible by AMF. Additionally, by maintaining root to shoot ratios biochar may have provided plants with N and P (through sorption of nutrients to surfaces or its inherent properties) when nutrients were more difficult to access. We also found variable plant responses across the two biochar types used. Understanding how nutrient and biochar additions can influence weed competition is important for anticipating potential undesirable consequences of novel soil amendments such as biochar.

A COMPARATIVE STUDY ON THE KINDS OF WEEDS OF PALM PLANTATIONS IN TABUK AND AL-QASSIM REGIONS IN SAUDI ARABIA

This study was aimed to investigate weeds kind in palm plantations. Date palm is the most chief economic crop in most countries of the Arabian Peninsula. Many factors, such as the presence of weeds, may cause a huge loss in the production of dates. Despite the severe damage caused by the presence of some weeds in agroecosystems, many weeds have many medicinal and economic uses. A total of 62 species were listed in palm Plantations in Tabuk and Al-Qassim Regions. A total of 51 species were listed in Tabuk Region (The number of unique species in the Tabuk Region reached 32 that not recorded in Al-Qassim Region. Also, 19 species were recorded in both of Tabuk and Al-Qassim Regions). A total of 30 weeds were listed in Al-Qassim Region (The number of unique species in the Al-Qassim Region reached 11 that not recorded in the Tabuk Region. In addition to, 19 species were recorded in both of Tabuk and Al-Qassim Regions). Zygophyllaceae was the most common family, the majority life span was annuals and the most common life form was therophyte in both Tabuk and Al-Qassim Regions. Data management and classification were achieved using PCORD (TWINSPAN and DCA analyses).

Improving pest monitoring networks using a simulation-based approach to contribute to pesticide reduction

Conventional pest management mainly relies on the use of pesticides. However, the negative externalities of pesticides are now well known. More sustainable practices, such as Integrated Pest Management, are necessary to limit crop damage from pathogens, pests and weeds in agroecosystems. Reducing pesticide use requires information to determine whether chemical treatments are really needed. Pest monitoring networks (PMNs) are key contributors to this information. However, the effectiveness of a PMN in delivering relevant information about pests depends on its spatial sampling resolution and its memory length. The trade-off between the monitoring efforts and the usefulness of the information provided is highly dependent on pest ecological traits, the damage they can cause (in terms of crop losses), and economic drivers (production costs, agriculture product prices and incentives). Due to the high complexity of optimising PMNs, we have developed a theoretical model that belongs to the family of Dynamic Bayesian Networks in order to compare several PMNs performances. This model links the characteristics of a PMN to treatment decisions and the resulting pest dynamics. Using simulation and inference tools for graphical models, we derived the proportion of impacted fields, the number of pesticide treatments and the overall gross margins for three types of pest with contrasting levels of endocyclism. The term “endocyclic” refers to an organism whose development is mostly restricted to a field and highly depends on the inoculum present in the considered field. The presence of purely endocyclic pests at a given time increases the probability of reoccurrence. Conversely, slightly endocyclic pests have a low persistence. The simulation analysis considered ten scenarios: an expected margin-based strategy with a spatial resolution of four PMNs and two memory lengths (one year or eight years), as well as two extreme crop protection strategies (systematic treatments on all fields and systematic no treatment). For purely and mainly endocyclic pests (e.g. soil-borne pathogens and most weeds, respectively), we found that increasing the spatial resolution of PMNs made it possible to significantly decrease the number of treatments required for pest control. Taking past observations into account was also effective, but to a lesser extent. PMN information had virtually no influence on the control of non-endocyclic pests (such as flying insects or airborne plant pathogens) which may be due to the spatial coverage addressed in our study. The next step is to extend the analysis of PMNs and to integrate the information generated by PMNs into sustainable pest management strategies, both at the field and the landscape level.

Biological management of allelopathic plantPartheniumsp.

AbstractGlobally, weeds have been considered as a major threat and act as a hindrance to crop production, even though the farmers put tremendous efforts to eliminate the weeds to get a better yield. Weeds stayed a steady threat to productivity and manageability of soil and environment, regardless of many years of research and advances in management practices.Parthenium hysterophorusis widely studied all around the world including India as a noxious and an unsafe weed responsible for many health risks in humans and animals. Many experts employed different biological methods using insects, beetle, microorganisms, and certain pathogens, which caused a broad dispersal damage toP. hysterophorus.Biorational weed control is also offered by allelopathy through the production of allelochemicals from the leaf, blossoms, grains, nuts, bud, berry, trunk, and organization of living or decaying plant substance. Allelopathy is the most realistic method to control the weeds as well as different plants. Lately, there has been a proliferation of curiosity to research on plant allelopathy to control weeds in agro-ecosystems. The successful management of this weed can only be achieved by an integrated approach with allelochemicals as a crucial aspect.

Rice allelopathy in weed management – An integrated approach

The intensive use of pesticides with low biodegradability and high persistence in soil, surface and ground waters, represents a considerable environmental risk, especially under high weed pressure conditions. Furthermore, the number of herbicide-resistant weeds is increasing. Against this background, the investigation of alternative weed control strategies has taken on considerable importance. Among these, allelopathy as a negative effect of one plant on another due to the direct or indirect (including microorganisms) release of chemicals in the environment can be a useful tool for the integrated management of weeds in agroecosystems. In particular, the paddies have been considered in this work by reviewing the data both on rice allelopathy and rice weed agronomic control methods developed to improve the crop yield.

Ethno-medicinal survey on weed plants in agro-ecosystems: a case study in Jahrom, Iran

Most useful plant-derived drugs have been discovered by follow-up of ethno-medicinal information. Weeds, unwanted and uncultivated plants in agro-ecosystems, generally tend to have high content of bioactive secondary compounds. The main objectives of present research were to gather, analyze, and evaluate the ethno-medicinal information on weed species used by the native people of Jahrom, Iran. All kinds of weeds were repeatedly collected from various agricultural areas through different seasons of 2015. Ethno-medicinal information about these weeds was obtained through direct interviews and open discussions with local informants. Based on the results, 36 weed species belonging to 18 families and 31 genera had traditional medicinal uses. Asteraceae was the most dominant family having highest number of weed species followed by Fabaceae, Brassicaceae, and Polygonaceae. Most of weeds with therapeutic uses had annual life cycle. Leaf was the most widely consumed part of the weeds followed by seed and fruit. The weeds were traditionally used for curing various health problems such as gastrointestinal disorders, body pain, and metabolic disorders. It can be concluded that certain weeds could play a major role in curing the diseases and health improvements in the local people, especially in developing countries. Undervaluation and ongoing destruction of the endemic medicinal weeds in agro-ecosystems may have a negative impact on availability of the unwritten local knowledge about such valuable weeds in the future.

Soil weed seedbank dynamic and allelopathic potential of <i>Tithonia diversifolia</i> (Hemsl)

The phenomenon of allelopathy is receiving increased attention as a possible alternative weed control method that is environment-friendly when compared with the use of herbicides with a wide range of toxic side effects which pose potential hazards to the environment. This study was designed to estimate the distribution of weed seeds in Tithonia diversifolia dominated fields and to evaluate the effect of leaf, stem and root extracts of T. diversifolia on the emergence of weed seeds in a southern Guinea savanna agro-ecology of Nigeria. To achieve the stated objectives, soil samples were taken from T. diversifolia dominated field and enumerated using direct seedling germination method. The phytosociological survey and growth parameters of T. diversifolia were assessed with the aid of permanently fixed quadrats measuring 0.5 m x 0.5 m placed at 1 m interval between quadrats during the rainy seasons (May– November, 2014 and 2015). The aqueous extracts of the leaf, stem, root and whole plant of T. diversifolia were prepared and applied to soil samples taken from different arable fields. The results of the study shows that 23 weed species belonging to 19 genera and 12 families were enumerated in the seedbank and 65 % of emerged weed seedlings were found between 0-10 cm soil depth. Digitaria gayana contributed (21.90 - 24.45 %), Brachiaria lata (17.07 – 19.24 %) while T. diversifolia (8.53 – 11.58 %). The similarity between the composition of the seedbank and that of the established vegetation was 24.42. The aqueous extract of the whole plant of T. diversifolia was found to have suppressed the emergence of 80.29 % weed seedlings, stems extract 79.57 %, leaves extract 74.35 % while the root extract suppresses 55.95 %. This study indicates that T. diversifolia has the potential to interrupt emergence of most weed species. It can further be used as a tool to formulate new eco-friendly bio-herbicides to control weeds in agro-ecosystems. Keywords: Allelopathy, Aqueous extracts, Seedbank, Tithonia diversifolia , Weed emergence

The effect of weeds on soil arbuscular mycorrhizal fungi and agronomic traits in spring wheat (Triticum aestivumL.) under organic management in Canada

Kubota, H., Quideau, S. A., Hucl, P. J. and Spaner, D. M. 2015. The effect of weeds on soil arbuscular mycorrhizal fungi and agronomic traits in spring wheat (Triticum aestivum L.) under organic management in Canada. Can. J. Plant Sci. 95: 615–627. Understanding the influence of weeds in agroecosystems may aid in developing efficient and sustainable organic wheat production systems. We examined the effect of weeds on soil microbial communities and the performance of spring wheat (Triticum aestivum L.) under organic management in Edmonton, AB, Canada. We grew 13 Canadian spring wheat cultivars in organically managed hand-weeded less-weedy and weedy treatments in 2010 and 2011. The less-weedy treatment exhibited greater grain yield and tillers per square meter, while kernel weight, test weight, days to maturity, plant height, grain P and protein content were not altered by weed treatment. Canada Western Red Spring (CWRS) wheat cultivars CDC Go and CDC Kernen were the most yield-stable because they minimized fertile tiller reduction in response to weed pressure (10 and 13% reduction, respectively, compared with the average reduction of 20%). Other cultivars exhibited yield stability through increased kernel weight. The contribution of arbuscular mycorrhizal fungi (AMF) to the total phospholipid fatty acid increased in both treatments; however, the rate of this increase was greater in the weedy treatment than the less-weedy treatment (from 2.9 to 3.9%, from 2.8 to 3.1%, respectively). Weed dry biomass was positively correlated with AMF% in the less-weedy treatment only. Organic systems tend to be weedier than conventional systems. We found that weeds are important determinants of AMF proliferation in soil. In addition, choosing wheat cultivars that maintain important yield components under severe weed stress is one strategy to maximize yields in organic systems.

Interactions between Sonchus oleraceus L. and some weeds in agroecosystems in Egypt

Interference of Sonchus oleraceus was studied by evaluating its competitive and allelopathic potential on three weed species: Brassica nigra, Chenopodium murale and Melilotus indicus. The allelopathic potential of S. oleraceus was assessed using the S. oleraceus-infested soil collected from its dominating communities and its root exudates trapped using living S. oleraceus, while its competitive ability was assessed in greenhouse in an additive design with ratio 1:1 at different densities. The rhizosphere soil of S. oleraceus inhibited germination and growth of B. nigra and M. indicus. Chlorophyll content of the target weeds was not affected in this test. Soils containing living S. oleraceus inhibited germination and growth of all weeds except germination of C. murale. Interspecific competition reduced germination of C. murale and M. indicus, and increased mortality of the former at all densities. HPLC analyses for soil samples indicated the presence of several phenolic compounds among which caffeic acid and catechol were abundant in the S. oleraceus-infested soil while caffeic and ferulic acids were abundant in its root exudates. The data suggest that both allelopathic and competitive potential of S. oleraceus function, and its interference plays at least a partial role in the community organization of weeds in agroecosystem.

Environmental Implications of Herbicide Resistance: Soil Biology and Ecology

Soil microbial community structure and activity are linked to plant communities. Weeds may alter their soil environment, selecting for specific rhizosphere microbial communities. Rhizosphere modification occurs for many crop and horticultural plants. However, impacts of weeds in agroecosystems on soil biology and ecology have received less attention because effective weed management practices were developed to minimize their impacts on crop production. The recent development of herbicide resistance (HR) in several economically important weeds leading to widespread infestations in crop fields treated with a single herbicide has prompted a re-evaluation of the effects of weed growth on soil biology and ecology. The objective of this article is to review the potential impacts of herbicide-resistant weeds on soil biological and ecological properties based on reports for crops, weeds, and invasive plants. Persistent weed infestations likely establish extensive root systems and release various plant metabolites through root exudation. Many exudates are selective for specific soil microbial groups mediating biochemical and nutrient acquisition processes. Exudates may stimulate development of microbial groups beneficial to weed but detrimental to crop growth or beneficial to both. Changes in symbiotic and associative microbial interactions occur, especially for arbuscular mycorrhizal fungi (AMF) that are important in plant uptake of nutrients and water, and protecting from phytopathogens. Mechanisms used by weeds to disrupt symbioses in crops are not clearly described. Many herbicide-resistant weeds includingAmaranthusandChenopodiumdo not support AMF symbioses, potentially reducing AMF propagule density and establishment with crop plants. Herbicides applied to control HR weeds may compound effects of weeds on soil microorganisms. Systemic herbicides released through weed roots may select microbial groups that mediate detrimental processes such as nutrient immobilization or serve as opportunistic pathogens. Understanding complex interactions of weeds with soil microorganisms under extensive infestations is important in developing effective management of herbicide-resistant weeds.

Avaliação do banco de sementes de uma área em processo de recuperação em cerrado campestre

Os estudos que tratam da interferência de plantas daninhas em agroecossistemas têm produzido resultados de pesquisa abundantes para campos de produção de grãos e pastagens; contudo, poucos trabalhos relatam o efeito da presença desse grupo de plantas em áreas degradadas isoladas para recuperação. Diante disso, este trabalho teve como objetivo avaliar a influência do banco de sementes no solo no processo de restauração ambiental de uma área representativa de cerrado campestre pela presença de plantas daninhas gramíneas. Para avaliação do banco de sementes, foram selecionados três ambientes: dois degradados e um ambiente-referência (conservado) de cerrado campestre. O procedimento de coleta das amostras de solo ocorreu em duas estações (seca e chuvosa), e as amostras foram avaliadas em 300 dias. Foram verificadas, durante a avaliação, apenas seis espécies nativas, e somente duas com hábito de vida arbóreo. A maior parte das sementes germinadas para os ambientes degradados, em ambas as coletas, foram identificadas como invasoras na área de estudo. Nesse sentido, o banco de sementes do solo local não é suficiente para que haja recuperação por meio da sucessão ecológica dessas áreas, sendo recomendado o uso de técnicas visando acelerar a restauração desses ambientes.

Reproductive strategies of Datura ferox, an abundant invasive weed in agro-ecosystems from central Argentina

Crop weeds develop in highly modified environments and are one of the most severe threats to agriculture worldwide, because their invasive nature determines competition for resources with crops and at the same time they can be hosts for pests and diseases. The information provided in this work is relevant both in scientific and technical terms, contributing to the design of effective strategies for the control of Datura ferox (Solanaceae). The aims of this work were to: (a) evaluate the reproductive strategies of D. ferox relative to fruit and seed production, (b) analyze the relationship between reproductive traits and persistence of these populations in agro-ecosystems of central Argentina, and (c) discuss different strategies to control crop weeds based on the knowledge of their reproductive ecology. D. ferox presented a great reproductive capacity that would not be constrained by limited pollen availability or pollinators in the populations studied. Flowers were pollinated by sphingids, coleopterans and Apis mellifera. The populations were self-compatible and autogamous; however, they exhibited higher fruiting percentages by natural pollination. Fruits produced by autogamy and geitonogamy had larger size and lower seed number and mass than those derived from natural pollination and xenogamy. D. ferox has combinations of traits (i.e., two flowering peaks, interactions with different pollinators, seed production after autogamy or xenogamy) that provide ecological advantages for establishment and survival processes in agro-ecosystems, hindering the species’ control. Control strategies might be improved if D. ferox abundance would be reduced before flowering to avoid fruit and seed production. This management strategy should be consistent over several years because the soil seed bank would allow population recovery in subsequent years.

Weeds in agricultural landscapes. A review

There is currently an increasing societal and political shift towards more sustainable agricultural systems to provide both food production and ecological biodiversity levels. This shift has recently modified scientific questioning and brought up new research challenges for agro-ecological research. This is the case in particular for weed management, where issues have so far largely focused on the conflict between weeds and crop productivity. Here, we review recent findings that have led to a changing perception on weeds in agro-ecosystems and upcoming areas in terms of weed management options. Our main findings are that weeds have numerous interactions with other organisms and, in turn, some of these interactions can have direct, either negative or positive, effects on the functioning of the agro-ecosystem. Many interactions are species-specific, and therefore assessing the role of weed communities in the agro-ecosystem would benefit from further development in the functional grouping of weed species. In terms of weed management our review shows that alternative cropping systems can deliver both good levels of crop productivity and of weed management at the field level. Weeds respond to landscape attributes and there is a need to fully assess the scope for utilizing the spatio-temporal organization of cropping systems and uncultivated habitats as a tool for minimizing weed infestations. Weeds are also submitted to biological regulation through the predation of their seeds and further research is required to assess the effect of cropping systems and landscape on levels of weed natural enemies, and therefore on the potential contribution of biological regulation in the management of weeds.

Spatial and temporal patterns of carabid activity-density in cereals do not explain levels of predation on weed seeds

Seed predation is an important component of seed mortality of weeds in agro-ecosystems, but the agronomic use and management of this natural weed suppression is hampered by a lack of insight in the underlying ecological processes. In this paper, we investigate whether and how spatial and temporal variation in activity-density of granivorous ground beetles (Coleoptera: Carabidae) results in a corresponding pattern of seed predation. Activity-density of carabids was measured by using pitfall traps in two organic winter wheat fields from March to July 2004. Predation of seeds (Capsella bursa-pastoris, Lamium amplexicaule, Poa annua and Stellaria media) was assessed using seed cards at the same sites and times. As measured by pitfall traps, carabids were the dominant group of insects that had access to the seed cards. In the field, predation of the four different species of seed was in the order: C. bursa-pastoris>P. annua>S. media>L. amplexicaule; and this order of preference was confirmed in the laboratory using the dominant species of carabid. On average, seed predation was higher in the field interior compared to the edge, whereas catches of carabids were highest near the edge. Weeks with elevated seed predation did not concur with high activity-density of carabids. Thus, patterns of spatial and temporal variation in seed predation were not matched by similar patterns in the abundance of granivorous carabid beetles. The lack of correspondence is ascribed to effects of confounding factors, such as weather, the background density of seeds, the composition of the carabid community, and the phenology and physiological state of the beetles. Our results show that differences in seed loss among weed species may be predicted from laboratory trials on preference. However, predator activity-density, as measured in pitfall traps, is an insufficient predictor of seed predation over time and space within a field.

Phenological and demographic behaviour of an exotic invasive weed in agroecosystems

Phenological and demographic behaviour of an exotic invasive weed in agroecosystems

Adaptability of plants invading North American cropland

Invasive species have received considerable attention in recent years, but research has primarily focused on invasive species of natural habitats. Furthermore, cropland weeds have often been viewed as possessing a “general-purpose genotype” and therefore exhibiting relatively static genetics. However, a more current view is that weeds are capable of rapid genetic change, thereby making analysis of their evolutionary ecology a potentially valuable component for the development of sustainable weed management systems. In particular, further analysis of ongoing evolutionary change in cropland weeds is important because (1) most cropland weed species exhibit considerable adaptability, (2) cropland agriculture is continuously changing, and (3) further research on weed adaptability is needed to design cropping systems to address evolutionary change. In this review, we examine the potential of cropland weeds to evolve so as to affect their invasiveness. There is abundant evidence of genetic variation within and among weed populations in traits relevant to invasiveness, including seed germination patterns, life history traits, physiological adaptability and adaptation to disturbance and resource fluctuations. Approximately half of cropland weed species are primarily selfing, and species with a high degree of selfing tend to exhibit homogeneity within populations but divergence among populations. We identified four critical areas for future research: conflicting selection pressures on weeds in agroecosystems, feed-back driven dynamics of human-weed co-evolution, co-evolutionary mechanisms of weed adaptation in conjunction with other weed species or organisms, and the role of weed evolution in the restoration of agroecosystems.