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1.
A survey was carried out on 72 sugarcane fields in Wonji-Shoa and Methara sugarcane plantations in the Rift Valley, Ethiopia, to determine the composition and distribution of weeds and to assess the influence of soil types and crop management practises on weed species composition and distribution. A total of 180 weed taxa belonging to 40 families was recorded. Poaceae, Asteraceae, Euphorbiaceae, Fabaceae, and Malvaceae were the most abundant families based on the number of species recorded. Annuals were more common (137 taxa) than perennials (43 taxa). The most frequent and problematic weed species in the plantations, irrespective of the soil types and crop types, were Cyperus spp., Sorghum spp., Euphorbia hirta , Ipomoea cordofana , Rhynchosia malacophylla , Datura stramonium , Launaea cornuta , Portulaca oleracea , and Amaranthus spp., with a frequency of > 65%. Perennial, rhizomatous Cyperus spp. were more dominant in ratoon crops than in plant crops. A partial canonical correspondence analysis (pCCA) showed that soil types, fertilizer application, and crop cycles were the major factors influencing the species distribution in the plantations among all the variables considered in the study. The first pCCA axis structured weed species associated with light-textured soil in contrast to weeds on heavy soil. D. stramonium , Tagetes minuta , and Galinsoga parviflora were mostly associated with light-textured soil, while Xanthium strumarium , Hibiscus trionum , Vigna fischeri , and Ipomoea eriocarpa were mostly associated with heavy-textured soils. The second axis distinguished those species associated with fields receiving fertilizers versus those that were not fertilized. Rottboellia cochinchinensis and Phyllanthus tenellus were mainly associated with fertilized fields while E. hirta and L. cornuta were common on unfertilized fields.  相似文献   

2.
Biological invasion by alien invasive species is now recognized as one of the major threats to native species and ecosystems. Parthenium weed ( Parthenium hysterophorus L.), an alien invasive weed species, is spreading throughout Pakistan. Worldwide, it has been designated as one of the most troublesome weed species. The adverse effects of this weed on human beings, livestock, crop production, and biodiversity are well-documented. As a result of a lack of information on its spread in Pakistan since its invasion, a phytosociological survey, with special reference to parthenium weed, was carried out in Islamabad from August–October 2002. Six main sectors of Islamabad were selected for sampling. The phytosociological survey of these sectors of Islamabad revealed a total of 30 weed species to be associated with P. hysterophorus . The survey also showed a high relative frequency, relative density, and importance value of P. hysterophorus in general; however, the percentage relative frequency of the weed in these sectors ranged from 10.6–30.3%. This survey revealed that P. hysterophorus had an appreciable degree of sociability with Senna occidentalis (L.) Link, Malvastrum coromandelianum (L.) Garcke and Lantana camara (L.). The data on the association of L. camara with P. hysterophorus suggests that a transition phase of competition or succession is in progress between these two alien species. The population of many common medicinal plants growing in the wastelands of Islamabad might be rapidly declining because of the aggressive colonization by P. hysterophorus . The ever-increasing infestation of this weed in urban areas also poses a serious threat to the health of the inhabitants of Islamabad.  相似文献   

3.
The germinable soil seedbank was determined at two sites in central Queensland on four separate occasions between February 1995 and October 1996. These sites were infested with parthenium weed ( Parthenium hysterophorus L.), a serious invasive exotic weed. During this period, the seedbank varied between 3282 and 5094 seeds m−2 at the Clermont site, and between 20 599 and 44 639 seeds m−2 at the Moolayember Creek site. Parthenium hysterophorus exhibited a very abundant and persistent seedbank, accounting for 47–73% of the seedbank at Clermont and 65–87% of the seedbank at Moolayember Creek. The species richness and species diversity of the seedbank, and the seed abundance of many species, was lower at Moolayember Creek during spring (the time of year when the most dense infestations of the weed originate). Parthenium hysterophorus seedlings also emerged more rapidly from the soil samples than did those of all other species. Hence, it seems that various aspects of the weed's seed ecology, including abundance and the persistence of its seedbank and the rapid emergence of its seedlings, are major factors contributing to its aggressiveness in semiarid rangeland communities in central Queensland. The domination by P . hysterophorus of the seedbanks of these sites suggests that the weed is having a substantial negative impact on the ecology of these plant communities. The diversity of these seedbanks was found to be lower in comparison with that observed in other grassland communities that were not dominated by an invasive weed species. Hence, the prolonged presence of P . hysterophorus may have substantially reduced the diversity of these seedbanks, thereby reducing the ability of some of the native species to regenerate in the future.  相似文献   

4.
Parthenium hysterophorus is a weed of global significance causing severe economic, environmental, human and animal health problems in Asia, Africa, Australia and the Pacific. In South Asia, P. hysterophorus occurs in India, Pakistan, Sri Lanka, Bangladesh and Nepal. A host-specific leaf-feeding beetle Zygogramma bicolorata from México was introduced into India in 1984, as a biological control agent for P. hysterophorus . In this study, a GIS-based distribution map of P. hysterophorus and its biological control agent Z. bicolorata in South Asia based on meta-analysis is presented. The map highlights the limited published information on P. hysterophorus incidence in many of the states and territories in India, as well as in neighbouring Bangladesh, Bhutan, Nepal and Pakistan. Incidence of Z. bicolorata was recorded as three distinct clusters, covering many states in India. In Pakistan, Z. bicolorata was recorded in the Punjab region bordering India. A CLIMEX model based on the current distribution of Z. bicolorata in India suggests that the geographic range of this agent in India and Pakistan can extend to other P. hysterophorus -infested areas in the region. The CLIMEX model also suggests that all of Bangladesh and Sri Lanka, and parts of Nepal are climatically suitable for Z. bicolorata.  相似文献   

5.
Cambodia has experienced a rapid shift from transplanted to hand broadcast seeded rice, with a consequent increase in seeding rates from 25–30 to 100–200 kg ha?1. To reduce costs, farmers keep their own seed for sowing with the risk of greater weed seed contamination of the sowing seed. A survey of weed seed contamination in harvested rice paddy was conducted in two provinces of Cambodia (Battambang and Takeo) at the end of the wet season in 2016. Farmers were interviewed about rice‐seeding practices, and a total of 110 farmers' fresh paddy samples were inspected for weed seed contamination from the two provinces. Sowing seed samples collected from 28 seed producer lots and 71 samples of farmer‐kept seed were also analysed for weed seed contamination. In both provinces, the majority of farmers kept their own seed or bought seed from a neighbour. Farm‐kept seed for sowing accounted for 88% of sown seed in Battambang and 89% in Takeo. Seeds of 41 different weed species from 13 plant families were found in the farmers' freshly harvested paddy samples. Overall, farmers managed to reduce the number of weed propagules by 60% and seed producers by 95%. There was no significant difference between farmer‐kept seed and seed producer/seed company seed for the total number of weed seeds present. When shown photos, farmers' rankings of the 10 most common weed species found in freshly harvested paddy did not closely correspond to the actual weed seed frequency in the paddy. When farmers were asked to rank the frequency of weeds in their fields without the option to choose from a list, they ranked the weeds differently. Farmers ranked Ischaemum rugosum, Echinochloa spp. and Fimbristylis miliacea as the three most frequent weed species in their fields. The most frequent weeds in harvested paddy, apart from weedy rice, were I. rugosum and Melochia corchorifolia. Farmers did not rank M. corchorifolia as a frequently occurring weed, and most farmers could not recognise M. corchorifolia from photographs. The priority for improved seed hygiene is to place the emphasis on assisting farmers to further improve their seed purification techniques and to caution them to inspect seed before purchasing from neighbours, seed producers and seed companies in the absence of the implementation of seed certification regulation.  相似文献   

6.
During the last decade, maize has become the crop with the second largest acreage in Germany. Therefore, agricultural advisors and the plant protection sector are interested in an overview of the weed species composition in maize fields, their determining factors and trends. From 2001 to 2009, a weed survey was conducted in 1460 maize fields throughout Germany. Data on crop management and soil characteristics were collected via farmer questionnaires. Principal component analysis and redundancy analysis were used to analyse patterns in weed species composition. The late spring and summer germinating species Chenopodium spp., Echinochloa crus‐galli and Solanum nigrum occurred with high densities and frequencies, but their occurrence was determined by different factors. Other frequent weed species were those that typically accompany autumn‐sown crops. The variation in species composition was significantly related to environmental factors (9.1% explained variance), particularly geographical latitude and precipitation, and management factors (4.7% explained variance), particularly crop sequence. The relative importance of these factors seems universal, when compared with surveys in other crops and regions. The factor ‘year’ was of minor importance (0.9% explained variance). Over the 9‐year period, no changes in weed species composition could be determined. The results suggest that despite the limited impact of crop management on weed species composition, farmers can use crop sequence to suppress individual species. The survey furthermore sets a baseline against which future changes can be measured in a landscape of rapidly changing agricultural land use.  相似文献   

7.

Two sets of field experiments were conducted at two sites (lowland and intermediate altitude) for 2 years in eastern Ethiopia to determine the influence of parthenium weed ( Parthenium hysterophorus ) density and duration of competition on grain yield of sorghum. In the first set of experiments, target weed densities of 0, 3, 7, 13, 27, 53 and 100 plants m -2 were used. Yield loss was severely affected by parthenium weed density, peaking at 97% at the lowland site in 2000. At this site, even very low density (e.g. three plants m -2 ) resulted in a high yield loss (69%). Owing to differences between sites and years, however, it was not possible to specify meaningfully the threshold densities for weeding. In the critical weed-free period experiments, four parthenium weed-infested and four weed-free periods from emergence to harvesting of sorghum were maintained by hand hoeing. The critical periods for weed control, i.e. the period over which weeding had the greatest benefit on yield, were 19 - 69 and 40 - 57 days from emergence of sorghum in 1999 and 2000, respectively, at the intermediate altitude (assuming an acceptable loss of 10%). In the lowland, however, it ranged directly from emergence to 61 and 66 days, indicating more severe competition at this site. The substantial variation in yield and yield loss between sites and years illustrates the problems of attempting to give well-established, accurate recommendations for threshold densities and critical periods in small-scale, rain-fed agriculture.  相似文献   

8.
广西麦冬草坪杂草调查及药剂防除试验   总被引：1，自引：0，他引：1  
2014-2015年对广西6个主要城市麦冬草坪杂草调查结果表明,麦冬草坪常见杂草有30科107种,其中菊科最多,有22种,占总数的20.56%,其次是禾本科13种,占总数的12.15%。危害较严重的有15种,依次为白花鬼针草、狗牙根、马唐、胜红蓟、香附子、铺地黍、阔叶丰花草、双穗雀稗、积雪草、龙葵、光鳞水蜈蚣、红花酢浆草、小飞蓬、银胶菊和升马唐。药剂防除试验结果表明,24%甲咪唑烟酸AS 324g/hm2、75%甲嘧磺隆WG 270g/hm2、50%丁噻隆SC 4 500g/hm2处理总草防效达80.37%~85.13%,对麦冬的抑制率达31.69%~70.91%;4%烟嘧磺隆SC180g/hm2、20%氯氟吡氧乙酸EC 360g/hm2+4%烟嘧磺隆SC 90g/hm2、5%精喹禾灵EC 90g/hm2+10%双草醚WP 90g/hm2、50%丁噻隆SC 2 250g/hm2+20%氯嘧磺隆WP 22.5g/hm2、75%甲嘧磺隆WG 135g/hm2+24%乙氧氟草醚EC 337.5g/hm2总草防效达81.07%~96.07%,对麦冬的抑制率为1.53%~8.46%。75%甲嘧磺隆WG 135g/hm2+24%乙氧氟草醚EC 337.5g/hm2总草防效达96.07%,对麦冬的抑制率为3.31%,适用于麦冬草坪杂草防除。  相似文献   

9.
To investigate the effects of agronomic practices and farmer demographics on levels of weed infestation in chickpea fields, a survey was conducted during 2015 in Sanjabi district, Kermanshah, Iran. Two sets of data were collected: (a) weed sampling from the selected chickpea fields, and (b) questionnaire recording of farmer demographics and agronomic management. The farmers were asked about their residence status (resident or migrant), occupation (farming only, farming plus a second job), experience and education levels, as well as seedbed preparation, sowing date and method, source of seed supply, crop cultivar, sowing seed rate, weed control operation and crop rotation history. The results showed that weed species composition was similar across the studied fields. The use of a row crop planter, a sowing rate of 45 kg ha‐1, and weed control resulted in 30.2, 23.03 and 34.2% reductions in weed infestation compared with hand sowing, a sowing rate of 30 kg ha‐1 and lack of weed control, respectively. Weed density decreased with increasing farmer experience and decreased by 33.0% and 23.5% in chickpea fields of resident farmers and owners whose sole occupation was agriculture. We found that 89.5% of the most experienced farmers adopted weed control operations and most resident landowners (77.4%) opted for crop planter (77.4%) and weed control (90.3%) compared to migrant farmers (50 and 68.5%, respectively). More landowners who were exclusively farmers performed weed control (90.6%) than owners who had a second job (67.9%).  相似文献   

10.
Parthenium hysterophorus, a native of Central America, is a problem weed of Australian rangeland, particularly in Queensland. Following field surveys in Mexico, the rust fungus Puccinia abrupta var. partheniicola was selected as a potential biological control agent. One isolate was chosen for further investigation after infection studies with one Kenyan and five Mexican isolates. Assessment of inoculation conditions showed that temperatures of less than 20° C and dew periods of more than 6 hours were required for abundant pustule production. Infection with the rust hastened leaf senescence, significantly decreased the life span and dry weight of Parthenium plants, and reduced flower production 10-fold. Subsequent host-range studies against 120 species and varieties, with further screening against a limited number of species conducted under a range of environmental regimes, indicated the rust to be sufficiently host-specific to be considered for introduction. Additional host-range tests against sunflowers demonstrated that resistance to P. abrupta var. partheniicola was not modified by prior inoculation with P. helianthi.  相似文献   

11.
In eastern Ethiopia, empirical information regarding farmers’ perceptions and implementation of research results about stem borer management is either scarce or unavailable. A survey of 120 farmers from four maize- and sorghum-growing districts of eastern Ethiopia was carried out in 2014 to study common management practices of cereal stem borers. Drought, pests, and land shortage were reported as the main constraints to maize and sorghum production in the area. Stem borers were perceived as the most important pests in these crops. The estimated yield losses from stem borers ranged from 10% to 50%. The majority of the farmers reported not using chemical insecticides to control these pests due to lack of capital, unavailability, and lack of knowledge. Moreover, most farmers were not using improved maize varieties. Cultural practices were found to be the most promising control method of cereal stem borers. Despite differences among districts, farmers practiced crop rotation, intercropping, manipulation of planting dates, crop residue disposal, and post-harvest tillage as common control strategies, even though a considerable proportion of the farmers was not implementing these practices sufficiently. The design of appropriate strategies for stem borer management based on farmers’ needs and priorities should be promoted.  相似文献   

12.
A study was conducted to assess the phytotoxicity of residues of Parthenium hysterophorus , an exotic invasive weed, towards the growth of three Brassica species ( Brassica campestris, Brassica oleracea and Brassica rapa ). The early growth of crops, measured in terms of seedling length and dry weight, was significantly reduced when grown in soil amended with varying amounts of Parthenium residues. A direct relationship was observed between the amount of residue incorporated in the soil and growth reduction. This adverse effect on Brassica crops indicates the presence of some growth-retardatory substances which are possibly released by the residues into the soil medium. In order to test this, aqueous extracts (1, 2, and 4%) of residues were prepared. It was observed that, in a laboratory bioassay, these extracts severely reduced the early growth of Brassica species, thereby indicating the presence of some water-soluble, inhibitory principles in Parthenium residues. A significant amount of the phenolics, the largest group of secondary metabolites usually implicated in allelopathy, was estimated in residue extracts, as well as in residue-incorporated soil. The phenolic content increased with increasing residue concentration, thereby showing their direct involvement in the observed growth inhibitions. Therefore, the study establishes that Parthenium residues exert an allelopathic influence on the early growth of Brassica crops by releasing water-soluble phenolics into the soil.  相似文献   

13.
This paper reports for the first time on farmers’ knowledge, perceptions and management practices of the fall armyworm (Spodoptera frugiperda) in Ethiopia and Kenya. A survey of 343 smallholder maize farmers was conducted. Most farmers in Ethiopia and Kenya had knowledge about fall armyworm; they could identify it mainly during its larval stage. Furthermore, most farmers in Ethiopia (93%) and Kenya (97%) encountered damage by fall armyworm in their farms. They estimated an average of 32% crop damage in Ethiopia and 47.3% of crop damage in Kenya, with an estimated yield reduction between 0.8 to 1 tonnes/ha. Nearly half of the farmers relied on chemical insecticides to control this pest. The majority (60%) of the farmers in Kenya perceived that insecticides were not effective in controlling fall armyworm as compared to most farmers (46%) in Ethiopia who perceived that chemical spray is effective for the control of fall armyworm. In Ethiopia, 26% of the farmers combined handpicking larvae with insecticide sprays, whilst 15% of the farmers practiced only handpicking. The present study highlights the need to develop management strategies for fall armyworm based on farmers’ needs and priorities.  相似文献   

14.
为明确山东省德州市棉田杂草发生、危害状况,于2013年对德州地区棉田杂草种类、出土规律及其群落自然消长动态进行了调查。结果表明：山东省德州市棉田杂草有19种,隶属于13个科,其中禾本科杂草的发生种类最多,而牛筋草、鳢肠和马唐的发生数量最为显著;田间共有3个杂草出土高峰,分别集中在5月中旬、6月底和8月中旬,前两个出土高峰中杂草的出土量较大;自然混生杂草群落内的总杂草数量在6月底达到峰值且在棉花整个生长季节内呈单峰变化。  相似文献   

15.
Parthenium hysterophorus is an invasive weed native to tropical and subtropical America. Since its introduction into China in 1926, this weed has been limited to southern areas (18°–25°N). However, new populations were recently reported in Shandong (35°N). The origin of this geographically isolated population remains unclear. In this study, we used inter simple sequence repeat and chloroplast DNA sequence markers ( trnQ-5'rps16 ) to investigate the genetic structure of 18 invading populations of P. hysterophorus and to examine the genetic relationship of Shandong and southern populations. Our data show that Shandong population is genetically different and has apparently higher levels of genetic diversity than most populations in southern China. Both neighbour-joining clustering and principal coordination analysis clearly separated Shandong from other populations. Chloroplast DNA sequence analysis further confirmed that the Shandong population was characterised by a unique haplotype that was not found in southern populations. We conclude that the population in Shandong may have been independently introduced from areas outside China. As P. hysterophorus has a broad potential distribution in China, attention should be paid to both international and domestic quarantine to prevent new introductions and curtail the possible hybridisation and gene flow between populations in different regions.  相似文献   

16.
The relative abundance of the weed functional types in dryland and irrigated rice in the Kharif (summer) crop field and dryland lentil and wheat in the irrigated Rabi (winter) crop field was studied at the agricultural farm of Banaras Hindu University, Varanasi, India. A total of 22 species, belonging to 17 families, was recorded in the dryland and irrigated rice ecosystems and 18 species, belonging to eight families, were recorded in the dryland lentil and irrigated wheat ecosystems. The Importance Value Index (IVI) of the hemicryptophytes showed an increasing trend with the crop growth period in the case of the dryland rice, whereas in the irrigated rice plots, a reduction in the IVI of the hemicryptophytes, with a related increase in the importance of the therophytes, was observed as the crop attained maturity. Also, the trend of a decreased IVI was observed for the geophytes in the fertilized dryland rice plots. The principal components analysis (PCA) ordination showed the uniqueness of the crop plot in terms of weed species composition. The PCA analysis of the functional types on the basis of the crop plots indicated that the hemicryptophyte and therophyte weed species composition was heavily altered at the initial and final sampling, although the weed flora was dominated by the therophytes and geophytes. These results suggest the prioritization of hierarchical temporal management options for the functional weed types in different crop plots and that this approach warrants further investigation.  相似文献   

17.
Weed species loss due to intensive agricultural land use has raised the need to understand how traditional cropland management has sustained a diverse weed flora. We evaluated to what extent cultivation practices and environmental conditions affect the weed species composition of a small‐scale farmland mosaic in Central Transylvania (Romania). We recorded the abundance of weed species and 28 environmental, management and site context variables in 299 fields of maize, cereal and stubble. Using redundancy analysis, we revealed 22 variables with significant net effects, which explained 19.2% of the total variation in species composition. Cropland type had the most pronounced effect on weed composition with a clear distinction between cereal crops, cereal stubble and maize crops. Beyond these differences, the environmental context of croplands was a major driver of weed composition, with significant effects of geographic position, altitude, soil parameters (soil pH, texture, salt and humus content, CaCO3, P2O5, K2O, Na and Mg), as well as plot location (edge vs. core position) and surrounding habitat types (arable field, road margin, meadow, fallow, ditch). Performing a variation partitioning for the cropland types one by one, the environmental variables explained most of the variance compared with crop management. In contrast, when all sites were combined across different cropland types, the crop‐specific factors were more important in explaining variance in weed community composition.  相似文献   

18.
Predicting the risk of weed infestation in winter oilseed rape crops   总被引：1，自引：0，他引：1  
Chemical weed control before crop and weed emergence is a systematic practice in winter oilseed rape crops in France. It would be profitable both for farmers and the environment to predict the level of weed infestation early on in the growing season and to control weeds only when necessary using post‐emergence weed control. The objective of this paper was to develop and evaluate simple models to predict weed biomass in oilseed rape crops. The model input variables were related to weed population characteristics and farmers’ practices. The models can be used to classify oilseed rape plots into two categories: plots with a level of weed infestation above a threshold or those with level of weed infestation below a threshold. A data set including 3 years of experiments, conducted across several regions in France, was used to estimate the parameters and to evaluate the models. High values of sensitivity and specificity were obtained when weed biomass was predicted as a function of sowing date, type of soil tillage, soil mineral nitrogen, crop density, weed density at emergence, and main characteristics of the most abundant weed species. Model performance strongly decreased when input variables related to the weed population were not taken into account. The best models correctly classified 90% of the plots with high weed infestation and 64% of the plots with low weed infestation.  相似文献   

19.
Parthenium or famine weed (Parthenium hysterophorus L.) is an annual plant originating from the Americas, which is a major invasive alien plant in almost all continents. While the deleterious impacts of the species on agriculture, human and animal health have been well documented, information on the pathways of entry of the species is only occasionally mentioned in the literature. As this invasive alien plant is only recorded as established in Israel and Egypt within the Euro‐Mediterranean region, the European and Mediterranean Plant Protection Organization identified P. hysterophorus as an emerging threat. EPPO therefore performed a Pest Risk Analysis on this species to assess the risk it represents and to consider appropriate management options. The EPPO Pest Risk Analysis main outputs are summarized in this article, indicating the probability of entry of the species via the different pathways within the EPPO region, its probabilities of establishment and spread, and the magnitude of its potential agricultural, environmental and social impacts.  相似文献   

20.
A Nowak  S Nowak  M Nobis  A Nobis 《Weed Research》2015,55(5):525-536
The influence of broad‐scale environmental factors on the species composition of segetal weed communities in Tajikistan was investigated. The research was conducted throughout the country, analysing plots of root crops as well as cereals from all phytogeographical regions of Tajikistan, with the exception of the eastern Pamir. The study was based on 440 phytosociological relevées sampled between 2009 and 2013 and analysed using direct and indirect ordinations. A set of environmental variables was obtained for each plot: altitude, mean annual precipitation, mean annual temperature, pH, crop type, longitude, latitude and date of sampling (seasonality). Crop type was the major factor determining species composition, which was related to the different farming practices in roots and cereals. Major changes in weed species composition were also driven by altitude and correlated temperatures. The seasonality of weed communities also had a considerable effect on weed community structure. Samples from spring differed significantly from samples from summer and late summer. Only longitude and soil pH were found to be insignificant. The complete set of environmental variables used in a canonical correspondence analysis explained 8.3% of the species variation in sampled plots. The study showed that despite the very diverse climatic conditions and low intensity of agriculture in Tajikistan, agrocoenoses respond mainly to the type of cultivation practised in arable land.  相似文献   

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