Importance Of Weeds Research Articles

The culm and glume anatomical study on Lolium (Poaceae) species in Iran

Lolium (Poaceae) is composed of five species in Iran that are of forage and weed importance. Culm and glume anatomy of grasses is inadequately explored. In the present study culm and glume anatomical structures of 17 population of four Lolium species is considered by use of 16 qualitative and quantitative features to distinguish Lolium species in Iran and to determine their diagnostic value. The culm cross-section showed multilayered hypodermis, ribbed or un-ribbed culm cross-sections, cuticles with different thicknesses, and the cortex with different tissues. Vascular bundles are arranged in two to more rings in the culm anatomy. Glume anatomical observations showed differences in girder attachment to vascular bundles, the outline of the cross-section, and the cortex tissue composition. The multi-variate statistical method based on culm and glume anatomical features showed that L. perenne and L. multiflorum are grouped near each other but there is more mixture between L. persicum and L. rigidum. Our findings are in agreement with the grouping pattern achieved by previous researches on leaf anatomy and lemma and palea micro-morphology of the same species. The molecular study by ISSR also provides support for the present study. The culm and glume anatomy of species studied provides valuable data for taxonomic purposes.

Cruciferous Weeds Do Not Act as Major Reservoirs of Inoculum for Black Rot Outbreaks in New York State.

Cruciferous weeds have been shown to harbor diverse Xanthomonas campestris pathovars, including the agronomically damaging black rot of cabbage pathogen, X. campestris pv. campestris. However, the importance of weeds as inoculum sources for X. campestris pv. campestris outbreaks in New York remains unknown. To determine if cruciferous weeds act as primary reservoirs for X. campestris pv. campestris, fields that were rotating between cabbage or had severe black rot outbreaks were chosen for evaluation. Over a consecutive 3-year period, 148 cruciferous and noncruciferous weed samples were collected at 34 unique sites located across five New York counties. Of the 148 weed samples analyzed, 48 X. campestris isolates were identified, with a subset characterized using multilocus sequence analysis. All X. campestris isolates originated from weeds belonging to the Brassicaceae family, with predominant weed hosts being shepherd's purse (Capsella bursa-pastoris), wild mustard (Sinapis arvensis), yellow rocket (Barbarea vulgaris), and pennycress (Thlaspi arvense). Identifying pathogenic X. campestris weed isolates was rare, with only eight isolates causing brown necrotic leaf spots or typical V-shaped lesions on cabbage. There was no evidence of cabbage-infecting weed isolates persisting in an infected field by overwintering in weed hosts; however, similar cabbage and weed X. campestris haplotypes were identified in the same field during an active black rot outbreak. X. campestris weed isolates are genetically diverse both within and between fields, but our findings indicate that X. campestris weed isolates do not appear to act as primary sources of inoculum for B. oleracea fields in New York.

Alternative hosts of Spongospora subterranea f. sp. subterranea in southern Africa

Spongospora subterranea f. sp. subterranea (Sss) is an obligate parasite that can only multiply within the living tissues of a host plant. Greenhouse experiments were carried out to determine the host status of Sss in some crops and weeds commonly found in southern African fields. These experiments used both qPCR and light microscope examination to study the development of Sss in the roots of weeds and crops grown in inoculated Merz solution. Zoosporangia and sporosori were observed microscopically in weed species Acanthospermum hispidum, Ageratum conyzoides, Bidens pilosa, Cleome monophylla, Datura stramonium, Euphorbia heterophylla, Oxalis latifolia, Physalis angulata, Setaria pumila and Tagetes minuta, whilst Ipomea plebia, Setaria verticillata and Galinsoga parviflora were non-hosts of Sss. Root galls were only observed on D. stramonium roots. The crops Allium cepa, Solanum lycopersicum, Zea mays, Avena sativa and Triticum aestivum were both zoosporangial and sporosorial hosts, whilst Phaseolus vulgaris and Brassica juncea were sporosorial hosts only. This study has added three new families to the hosts of Sss, namely Oxalidaceae, Euphorbiaceae and Cappardaceae. Two zoosporangial hosts were identified, namely Avena strigosa and Glycine max. These crops would be ideal to be included as trap crops in rotations with potatoes. The highest quantity of Sss DNA in weed species was recorded in the roots of P. angulata, N. physalodes and A. conyzoides, whilst in cultivated crops the highest quantity of Sss DNA was recorded in Brassica juncea followed by Avena strigosa. The study has shown the importance of weeds and some crops used in rotation with potatoes as alternative hosts of Sss and their potential to increase Sss inoculum level in the soil.

Population Structure of Fusarium graminearum Isolated from Different Sources in One Area over the Course of Three Years.

Fusarium head blight (FHB) is an important crop disease worldwide and is mainly caused by members of the Fusarium graminearum species complex. F. graminearum sensu stricto is the most common cosmopolitan and predominant FHB causal agent in Europe. Thus far, the majority of studies have focused on the primary hosts (wheat and barley) of this pathogen, while the relationships between other sources of infection remain unclear. We monitored and sampled test fields over the course of 3 years and acquired 804 F. graminearum isolates from different sources: primary hosts and other plant species included in the crop rotations, weeds from the test fields, decaying plant residue, soil samples, and crop seed. Of these isolates, 73.3% had the 15-acetyldeoxynivalenol genotype and 26.7% had the 3-acetyldeoxynivalenol genotype. F. graminearum isolation rates from weeds (>50%) were much higher than from soil (< 10%) or decaying plant matter (4%). Variable number of tandem repeat markers were used for population analysis. Noticeable genetic differentiation was detected between isolates from living plants and soil biome. In contrast, absence of any noticeable division between primary and alternative plant host communities indicates the importance of weeds and other segetal plants for FHB control and prevention.

Evaluation of Datura stramonium and Nicandra physaloides as reservoirs of tomato severe rugose virus and whiteflies

AbstractTomato severe rugose virus (ToSRV) is the most important begomovirus transmitted and spread by the whitefly Bemisia tabaci in tomato crops in Brazil. Cultural practices are being adopted, along with insecticides, for controlling this virus. However, little is known about the importance of weeds in the pathosystem, which can contribute to the failure of these practices. This work aimed to evaluate the role of Datura stramonium and Nicandra physaloides as alternative hosts of ToSRV and verify the viral influence on the biological performance of Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species. N. physaloides was a better alternative host for ToSRV when combined with MEAM1 whiteflies, while D. stramonium was mostly a good host for whitefly reproduction. Viral infection improved MEAM1 performance on both host plants but affected MED performance negatively. These data suggest that both weeds can be of some importance for the pathosystem, and their control should be included in management programmes.

Weed species within cereal crop rotations can serve as alternative hosts for Fusarium graminearum causing Fusarium head blight of wheat

Abstract Fusarium graminearum is the main causal agent of Fusarium head blight (FHB) of small grain cereals, but the importance of weeds in the FHB disease cycle and the establishment of F. graminearum in agroecosystems are still not fully understood. The objective of this study was to determine the potential role of weeds present within cereal crop rotations as alternative hosts. F. graminearum was isolated from different organs of asymptomatic weeds sampled from six fields with cereal-crop rotations in Lithuania for two consecutive years (2015 and 2016). The fungi were identified using morphological and molecular methods. Out of 57 weed species that were investigated, 41 (71.9%) harboured F. graminearum isolates. Twenty five weed species were identified as new, previously undocumented, hosts. The majority (73.3%) of the isolates of F. graminearum from this study belonged to the 15ADON genotype while a smaller proportion (23.4%) belonged to the 3ADON genotype. All F. graminearum isolates that were assessed induced FHB symptoms on artificially inoculated spring wheat tested in the field.

Smart weed management: A small step towards doubling farmers’ income

Increasing incomes by reducing crop losses due to various pests and improving productivity and input-use efficiency, are some of the major recommendations of the report on Doubling Farmers’ Income by 2022. Weeds are unwanted intruders into agro-ecosystems that compete for limited resources and reduce crop yields and farmers’ income. It was estimated that on an average the weed control costs around INR 6000/ha (USD 92.42/ha) in rainy season crops and around INR 4000/ha (USD 61.61/ha) for winter crops, which accounts for around 33% and 22% of total cost of cultivation, respectively. Thus, efficient weed management can help in increasing the farmers’ income by reducing the losses caused by weeds, decreasing the cost of production, and increasing the productivity through efficient utilization of resources. The present paper deals with the importance of weeds in crop production and farmers’ income, and role of smart weed management practices in reducing cost of production, and improving input-use efficiency and crop productivity.

The importance of weeds as melliferous flora in central Chile

The importance of weeds as melliferous flora in central Chile

Ethnopharmacological values of weeds in Eastern Uttar Pradesh, India

Weeds may be potential source of useful drugs if they are evaluated through proper identification, characterization, and biochemical screening. The main goal of this study was to know the importance of weeds in the modern medicine sector and addresses their implications for public health. The ethnomedical data of weeds were collected through semi-structured interviews of fifty four healers, group discussion, and field observation. According to the results, weeds have been an exemplary source of medicine in human health care system. The present paper reviews 24 weeds of medicinal importance that have been mostly used by tribal people for the treatment of several diseases like respiratory, stomach, kidney disorders, diabetes, wounds healings, etc. The most commonly used drugs of modern medicine such as atropine, berberine, vinblastine and vincristine (anti-cancers), digitalis, etc., have been originated from weeds. Therefore, weeds are one of the best choices in establishing a new way for drugs development in herbal medicine sector. Key words: Weeds, medicinal plants, phytopharmacological study, chemical composition, drugs, traditional value.

Ervas daninhas como hospedeiras alternativas de patógenos causadores do colapso do meloeiro

The vine collapse is an important melon (Cucumis melo) disease in Brazil and worldwide. Little is known about the importance of weeds as alternative host of melon collapse pathogens. During this research, the prevalent weeds were collected in four fields of melon production in the Brazilian Northeast during the period between two consecutive growing seasons and the fungi associated with the root systems were isolated in pure culture. The weeds collected belonged to 16 species and 11 botanical families. Among the fungi causing melon vine collapse, from weed roots were isolated Macrophomina phaseolina and Rhizoctonia solani. The first fungi was observed in all fields and isolated from 13 weed species, any previously registered as fungi host, while the second was detected only in a single botanical species and one field. Therefore, weed control in between melon growing seasons is essential for success in the management of the vine collapse of the melon when M. phaseolina predominates among the possible root pathogens.

First Report of the Root-Knot Nematode Meloidogyne arenaria on Cheeseweed Mallow (Malva parviflora) in the United States

During a 2010 field trial for examining alternatives to methyl bromide soil fumigation for the production of field-grown cut flowers, weeds were collected for identification and evaluated for their potential as hosts for plant pathogenic nematodes. In one cut flower field located in Martin County, FL, six cheeseweed mallow (Malva parviflora L.) plants were collected that had root-galling typical of infection by a root-knot nematode (Meloidogyne spp.). Field collected plants were used for species identification of the weed and maintained in the greenhouse for seed production. Several gravid female nematodes were extracted from field collected mallow roots and individually identified as Meloidogyne arenaria based on their esterase phenotype (PhastSystem, GE Healthcare) (1). A single egg mass was then extracted from the field collected mallow roots and inoculated onto a tomato plant (Solanum lycopersicum, 'Rutgers') grown in steamed builders sand in the greenhouse. The single egg mass culture was increased for 8 weeks, until galling was sufficient to produce adequate nematode inoculum to complete Koch's postulates on the original mallow host. Ten mallow plants were inoculated with single egg masses originally isolated from mallow and increased on tomato. Ten additional plants were maintained in the greenhouse as uninoculated controls. Inoculated and control mallow plants were grown in the greenhouse for 8 weeks, after which the roots were evaluated for galling, and root-knot nematode J2 were extracted from roots and soil and counted. All inoculated plants produced galled roots and control plants did not. Gravid females were extracted from mallow roots and identified as M. arenaria based on esterase phenotype as previously described. Ten gravid females for each DNA extraction were collected from mallow roots and DNA was isolated with the PowerSoil DNA Isolation Kit (MO BIO Laboratories, Inc., Carlsbad, CA). Identification of M. arenaria was confirmed by using species-specific primers F5'-TCGAGGGCATCTAATAAAGG-3' and R5'-GGGCTGAATAATCAAAGGAA-3' (2) and F5'-TCGGCGATAGAGGTAAATGAC-3' and R5'-TCGGCGATAGACACTACAACT-3' (4), which produced single amplicon bands of the expected size of 420 and 950 bp, respectively. This weed species has been reported as a host for M. javanica in Algeria and as an experimental host in Egypt (3), but this report, to our knowledge, constitutes the first documentation of Malva parviflora as a natural host of M. arenaria. The importance of weeds as hosts for plant parasitic nematodes cannot be over emphasized. As growers, particularly in Florida and California, continue to lose tools for broad-spectrum pest control, the ability of nematodes to reproduce on uncontrolled weeds will become increasingly important.

Imperfect Balance: Landscape Transformations in the Precolumbian Americas (review)

Reviewed by: Imperfect Balance: Landscape Transformations in the Precolumbian Americas William E. Doolittle Imperfect Balance: Landscape Transformations in the Precolumbian Americas. David L. Lentz, (ed.) New York: Columbia University Press, 2000. 547 pp., maps, photographs, diagrams, charts, tables, references, and index. Paper $44 (ISBN: 0-231-11157-6). We all occasionally miss something that we shouldn't. I say "we" trusting that I am not the only one who has experienced the chagrin of discovering an important publication that slipped under his or her proverbial radar. Indeed this is exactly what happened in the case of this Imperfect Balance, a book that came to my attention more than 10 years after its publication. I could take responsibility for this oversight and admit to being remiss. I won't, however, because I continue to be baffled by the number of scholars I meet who should know of a book I published in 2000, but do not. Accordingly, I lay full responsibility for my not knowing about this book square on the shoulders of the marketing department of the publisher. Those folks clearly did not do a good job of advertising and promoting their product. Shame on them! This is a magnificent volume. It consists of 15 chapters that provide uniform and total coverage of the Americas. A few of these are topically and regionally broad, emphasizing biophysical environments with limited acknowledgment of human presence. Chapters 3 and 11, for example, barely mention people as either agents or victims of change. The former by Andrew M. Greller, and the latter by James L. Luteyn and Steven P. Churchill, deal with vegetation in North and Central America, and the Andes, respectively. David A. Hodell, Mark Brenner, and Jason H. Curtis authored Chapter 2 which discusses climate change in the northern American tropics and subtropics since the last ice age. It devotes only three pages to the human element and part of this explores future implications. [End Page 250] Six chapters are of a local or regional nature and deal with one of my favorite topics—agricultural landscapes. A finer set of authors, each a distinguished scholar in her or his own right, could not have been found. Progressing from South to North are contributions by Clark Erickson on the Titicaca Basin, Charles Spencer on Venezuela, Nicholas Dunning and Timothy Beach on the Yucatan, Emily McClug de Tapia on the Basin of Mexico, Suzanne K. Fish on the Sonoran Desert, and Gayle J. Fritz on the Mississippi River Valley. Three chapters on South America are particularly interesting individually and in concert. Terence N. D'Altroy portrays land use in the Andes using a standard classification system, but also deals with the exchange of products between sub-regions, and ends with some insightful comments on cultural ecology and cultural ideology. Lowland tropical vegetation is discussed with some interesting twists. Its coauthors, Douglas C. Daly and John D. Mitchell, include sections on folk classifications, structures, inclusions, and transitions. Finally, Anna C. Roosevelt's contribution, Chapter 15, will need some revision given the abundance of recent research on terra preta, or dark earth, but I like her argument that the lower Amazon is a dynamic human habitat. Saving the best for last, or nearly so, my two favorite chapters (4 and 8) deal with anthropocentric food webs, and silviculture and forest management, respectively. In the former, David L. Lentz provides an abundance of data, much of them in tabular form, for what I have dubbed the husbandry of wild plants. Some of these were the ancestors of domesticated crops, some of them were not. With an emphasis on the importance of weeds and pioneers, this chapter surely would meet with the approval of the late Jack Harlan, one of my domestication heroes. The enrichment of useful species, the management of forests and fallowed plots, and home gardens are topics that comprise Chapter 8 by Charles M. Peters. As with any edited volume, this collection of specially-authored works begins with a chapter outlining concepts and providing definitions, and ends with a summary and conclusions. Although only one chapter was written by geographers (Dunning and Beach), Imperfect Balance bears a geographical imprimatur, in the form of a Foreword...

Weed Hosts of Root-Knot Nematodes Common to Florida

ENY-060, a 7-page illustrated fact sheet by Jim Rich, Janete Brito, Jay Ferrell, and Ramandeep Kaur, discusses the importance of weeds as nematode hosts, and how knowledge of symptomatic weed hosts can monitor fields for nematodes. Includes a table of selected Florida weeds occurring as hosts of root-knot nematodes. Published by the UF Department of Entomology and Nematology, April 2010.

The importance of weeds in ethnopharmacology

Tropical primary forest is often considered to be the most important habitat for traditional peoples to gather medicinal plants. However, the role of weeds, commonly found in disturbed areas, in traditional medicinal floras has been overlooked. Data are presented showing the significant representation of weeds in the medicinal floras of the Highland Maya in Chiapas, Mexico and in the medicinal flora of Native North Americans as a whole. The frequency with which weeds appear in these pharmacopoeias is significantly larger ( P<0.0001) than what would be predicted by the frequency of weed species in general. Explanations based on human ecology and biochemical ecology are presented.

The Status of Biological Control of Weeds with Fungal Pathogens

Weeds continue to cause major problems in agriculture throughout the world, reducing yield and quality of crops by competing for the water, nutrients, and sunlight essential for vigorous crop growth. The importance of weeds is reflected by the rapid growth of the use of chemical herbicides in agriculture throughout the world. The effectiveness of herbicides has dramatically in­ creased yields in many cases and, in turn, stimulated development of new chemical herbicides. However, despite massive efforts, weeds continue to cause significant losses. These losses result from the selection and emergence of species that are not controlled by currently available herbicides, the inability of a herbicide to selectively control certain weedy species without injury to crop species, or the development of resistant strains. Plant pathogens have been suggested as one of several possible means of controlling the weeds that remain problematic in otherwise successful weed control programs in intensive agriculture or even as an alternative to chemical herbicides. Plant pathogens, along with insects, are also being considered as a potential cost­ effective means of reducing weed populations in crops, forests, or rangelands where low profit margins preclude large herbicide expenditures. Biological control of weeds with plant pathogens has been the subject of numerous reviews and several books, and the reader is referred to these for additional information (13, 15, 73, 78). This review concentrates on selected

Nature and importance of weeds in sorghum in the Yemen Arab Republic

Abstract Grain sorghum (Sorghum bicolor (L.) Moench) is the dominant crop in North Yemen agriculture, covering about 70–80% of the arable land. Weed control is still carried out mainly by hand. Many of the weeds are used as fodder for animals. A total of 137 weeds was collected in sorghum. Most frequent were Cynodon dactylon (L.) Pers. and Cyperus mtundus (L): their importance decreased, however, under a well‐established sorghum crop providing good shade cover and under conditions of increased crop fertilization with mineral nitrogen. Under these conditions, for example, Commelina spp. and Flaveria trinerva (Spreng.) Mohr became commoner. Thus increased use of nitrogen altered the nature and hierarchy of the weed flora. Relationships between the indicator figures of the weeds and the habitat, as defined by Ellenberg, were confirmed. Traditional methods of weed control have so far worked well, as witness an average cover of 60% sorghum and 20% weeds. In future, however, rising costs and labour shortages wi...

Seeding year alfalfa population development as influenced by weed competition and density of establishment

The research in intraspecific competition within an alfalfa stand and interspecific competition between alfalfa and weeds was begun on the Michigan State University farm in East Lansing in 1972. Alfalfa seeding densities of 50, 400 and 800 seeds/m2 were used to determine intraspecific competition. Interspecific competition between alfalfa and weeds occurred mainly in noncontrolled alfalfa stands at various levels of seeding densities. Plant competition was evaluated with importance values and with relative crowding coefficients. Both measurements were found to be suitable for this kind of study. Importance values primarily indicated the quantity relationships of different species. Relative crowding coefficients mainly characterized the competitive ability of a species in a mixed stand. The importance of alfalfa exceeded the importance of weeds in noncontrolled and herbicide controlled stands at the seeding rates of 14 and 7 kg/ha respectively. Relative crowding coefficients show the competitive ability of alfalfa with regard to weeds. In the case of intraspecific competition there was no change in the crowding coefficient of alfalfa in respect of weeds when the seeding rate of alfalfa was increased beyond 9 kg/ha. The crowding coefficient of weeds presented equal values under all treatments thereby indicating the variability and plasticity of weeds. The maximum yield level was obtained in all treatments with the alfalfa seeding rate of 9 kg/ha. The total biomass production per unit area was equal in the noncontrolled system at all seeding densities and in the herbicide controlled system at seeding rates of 9 kg/ha or more.

PATHOGENIC SPECIES OF VERTICILLIUM IN HORTICULTURAL CROPS AND WEEDS IN SOUTHWESTERN ONTARIO

Verticillium wilt is an important disease of many horticultural crops in Essex County of southwestern Ontario. Verticillium dahliae is the predominant pathogenic species, being isolated from all susceptible crops and also from a few common weeds. V. albo-atrum, a virulent pathogen, and V. nigrescens, a weak pathogen, are isolated almost exclusively from potato (Solanum tuberosum L.). V. albo-atrum is virtually dependent on the potato crop for its existence in Essex County. The importance of weeds in the perpetuation of V. dahliae in cropped areas is emphasized.

The importance of weeds and the correct timing of weed control measures in maize crops

The importance of weeds and the correct timing of weed control measures in maize crops