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1.
In Germany, sugar beet is often rotated with 2 years of cereal. Extensive fallow periods between cereal harvest and autumn primary tillage allow for a weed flora to develop. Broad‐leaved weeds could potentially be alternate hosts for the common nematode Heterodera schachtii, one of the most important pests of sugar beet. Between 2009 and 2012, annual weeds developing in cereal stubble fields during July to mid‐October in the season prior to sugar beet were surveyed, including known hosts of H. schachtii. Yearly weather patterns and agronomic practices possibly impacted weed species composition and weed population densities. During September, Chenopodium album, Cirsium arvense, Convolvulus arvensis, Mercurialis annua, Polygonum spp., Solanum nigrum and Sonchus spp. occurred at the highest frequencies. Weed hosts of H. schachtii were present, but densities, frequencies and uniformity were limited. In 2010 and 2011, staining for nematodes in roots revealed juvenile penetration of some weeds but few adult stages. No indication of nematode reproduction of H. schachtii was found on these weed hosts. A fairly stable weed flora was detected on stubble fields that could provide some carry over for weed species. An elevated risk for nematode population density build‐up on these weeds was not found and management of these weeds at the observed densities during the stubble period for nematological reasons appeared unnecessary.  相似文献   

2.
A survey of grass weeds of cereals in central southern England made in 1981 was repeated in 1982 between 28 June and 23 July. Dicotyledonous weeds were also assessed in 1982. A total of 1021 fields were surveyed, 702 in winter wheat. 198 in winter barley and 121 in spring barley. A total of twenty-four grass weeds were found and their levels of infestation were scored. The most frequently found grass weeds were the same as in 1981. In all cereals combined, these were Elymus (Agropyron) repens in 35% of fields, Avena fatua in 32%, Alopecurus myosuroides in 26% and Poa trivialis in 24%. Sixty-three species of dicotyledonous weeds were recorded and of these, eighteen species occurred in 2% or more of fields. The eight most frequent were Viola arvensis, Galium aparine, Stellaria media, Myosotis arvensis, Polygonum aviculare, Convolvulus arvensis, Bilderdykia (Polygonum) convolvulus and Lamium purpureum. Most species were fairly uniform in distribution, but Galium aparine, Convolvulus arvensis and Cirsium arvense were most frequent in the east while Viola arvensis was least frequent there. The cereals varied in weediness, 32% of winter barley, 23% of spring barley and only 7% of winter wheat fields had no weeds recorded.  相似文献   

3.
In 962 field trials in different crops, the size of a number of weed species was investigated. The weeds were ranked according to their size on a single occasion. The ranks of the species were examined relative to two weed species, Viola arvensis and Matricaria inodora. The ranking was, however, independent of which of the two species were used as standard. The correlation between the rankings with Viola arvensis as standard, and the rankings with Matricaria inodora as standard were r= 0-93 for spring sown crops, and r= 0.84 for autumn sown crops. Sinapis arvensis was the largest weed species in spring sown crops, with a weight of 14.5 times that of Viola arvensis, followed by Brassica napus, Galeopsis spp., Thlaspi arvense and Amsinckia spp. Viola arvensis. Veronica spp. and Lamium spp. were the smallest weed species in spring sown crops. Galium aparine was the largest species in autumn sown crops, whereas spring germinating species such as Polygonum spp. were among the smallest. The ranks of Viola arvensis, Myosotis arvensis, Lapsana communis, Matricaria inodora and Lamium spp. were almost identical in spring sown crops and in autumn sown crops.  相似文献   

4.
Weeds are a primary factor limiting maize yield. Their occurrence and abundance are affected considerably by environmental factors and farming practices. The variability of weed number in maize depending on the soil type and farm size was investigated. Farms of different sizes vary in farming practices, which affects weediness. Based on this assumption, farm size was considered as indirect factor affecting weed abundance. An investigation of 45 farms that differed in size (5–15 ha, 15–50 ha, >50 ha) and soil type (chernozem, distric cambisol, haplic luvisol) was conducted. Thirteen dominant weed species persistently occurring in maize fields in south-western Poland were examined. Regardless of the soil type and farm size, the most abundant weed species were Echinochloa crus-galli and Chenopodium album. In addition to these species, the most numerous weeds on chernozems were Setaria viridis and Solanum nigrum, while on haplic luvisols and distric cambisols, the most numerous were Viola arvensis and Elymus repens. Additionally, on haplic luvisols, Anthemis arvensis was abundant. Small farms were stronger infested by weeds than large farms due to the implementation of extensive weed-supressing practices, especially low herbicide use. Soil type affected the number of weeds to a greater extent than did farm size.  相似文献   

5.
A glasshouse experiment was carried out to investigate the influence of increasing levels of nitrogen and phosphorus on the growth of six common weed species growing alone or in competition with spring barley (Hordeum vulgare). Capsella bursa‐pastoris, Chenopodium album, Papaver rhoeas, Sinapis arvensis, Spergula arvensis, Viola arvensis and spring barley were grown in pots with different levels of nitrogen (0, 30, 60, 90, 120 and 150 kg N ha?1) or phosphorus (0, 10, 20, 30, 40 and 60 kg P ha?1). The aboveground parts of the plants were harvested after 7 weeks and the dry weight of shoots, percentage N and P content of the shoot and uptake of N and P were determined. A linear or a polynomial model was used to describe the data. Growing alone, Spergula arvensis was the only weed species that increased its dry weight at the same rate as barley. Weed species with low dry weight increase had larger increases in percentage N or P content than barley, indicating a luxury accumulation of nutrients. The uptake of N and P per pot did not differ much between weeds and barley. V. arvensis and P. rhoeas accumulated least nutrients (per cent of dry matter) and Spergula arvensis accumulated most. Weeds grew poorly in competition with barley. The percentage N and P content in barley did not change when they grew in competition with weeds.  相似文献   

6.
Trials were carried out in order to investigate ways in which to achieve selectivity in mechanical weed control. The influence of soil type, uprooting angle and development stage on the uprooting force of some annual weeds and carrot was studied. Spergula arvensis L., Urtica urens L., Chenopodium album L. and carrot (Daucus carota L.) were sown in soil bins filled with four different soil types. The plants were uprooted when they had two true leaves. Soil type significantly influenced the uprooting force needed by all four species. The forces required to uproot U. urens and C. album differed significantly between peat and loamy sand. In loamy sand, Capsella bursa-pastoris (L.) Med., Stellaria media (L.) Vill, Chamomilla suaveolens (L.) Pursh Buch. and Viola arvensis Murr. could all be uprooted by less force than it took to uproot carrot. The uprooting angle (0°, 45° and 90°) had no significant influence on the uprooting force for carrot at the studied developmental stage. C. album, S. arvensis, U. urens, Matricaria inodora, Thlaspi arvense L. and carrot could all be uprooted by less than 1 N when they had two true leaves. Carrots required a greater uprooting force than the weeds at the three early developmental stages studied. This indicates that it should be possible to develop selective mechanical weed control methods.  相似文献   

7.
In Europe, sugar beet is often produced in a 3‐year rotation with cereals, leaving stubble fields fallow from cereal harvest until primary tillage in autumn in the year prior to sugar beet production. The weed flora on such fields could include host plants of Heterodera schachtii that is one of the most important pests of sugar beet. Crop sequences with non‐hosts and cover cropping with resistant cruciferous hosts during this period have been crucial for its management. Availability of resistant and tolerant sugar beet cultivars could entice growers to forego cover cropping, exacerbating weed problems during the fallow period. The objective of this study was to determine the reproductive potential of H. schachtii on weeds that develop during this period. Under glasshouse conditions, reproduction on 39 plant species was compared with that on oilseed radish and sugar beet of differing nematode host status. In 2 years in field microplots, 18 previously tested species were grown in H. schachtii‐infested soil during the typical fallow period at 60 plants m?2, and nine of these species were also grown at 180 plants m?2. There were variable results between years after 8 weeks of growth, but most weeds allowed lower reproduction (<10%) than the susceptible sugar beet; only Stellaria media at 180 plants m?2 and Thlaspi arvense at both plant densities increased nematodes. Such weed densities may seldom occur under commercial conditions; thus, weed management for nematological considerations during the stubble period may have limited importance.  相似文献   

8.
The pre- and early post-emergence herbicidal activity of diflufenican, a novel herbicide, is reported and attention is drawn to its ability to control important weeds in winter cereals, including Galium aparine, Veronica hederifolia, Veronica persica and Viola arvensis, which are resistant to substituted-urea herbicides. The synthesis of a series of related compounds is described and the relationship between structure and activities against a range of plant species is examined in respect of changes in the phenyl, phenoxy and pyridine rings. The design and synthesis of a small number of compounds combining the best patterns of substitution in each of the rings is described. The resulting optimisation of herbicidal activity in the series is reported, together with field trial results comparing the herbicidal efficacy, crop selectivity and soil persistence of the most active structures.  相似文献   

9.
Predicting the growth and competitive effects of annual weeds in wheat   总被引：1，自引：0，他引：1  
The growth and competitiveness of 12 annual weed species were studied in crops of winter wheat, in which weeds were sown to give a wide range of plant densities. Weed growth patterns were identified; early species which senesced in mid-summer were less competitive than those with a growth pattern similar to that of the crop. Most species had little effect on crop yield in 1987, and this was attributed to a high crop den sity. Crop yield-weed density relationships for all species in 1988 and for Galium aparine in 1987 were well described by a rectangular hyperbola. Species were listed in the following competitive order based on the percentage yield loss per weed m?2: Avena fatua > Matricaria perforata > Galium aparine > Myosotis arvenis > Poa trivialis > Alopecurus myosuroides > Stellaria media > Papaver rhoeas > Lamiumpur-pureum > Veronica persica > Veronica hederi-folia > Viola arvensis. Prediction of yield loss is discussed. The assumptions inherent in using Crop Equivalents (based on relative weights of weed and crop plants), are challenged; with intense competition, weed biomass at harvest failed to replace lost crop biomass, and harvest index was reduced. It is concluded that a competi tive index, derived from yield density relation ships, and expressed as the percentage yield loss per weed m?2, is more likely to reflect the com petitive ability of a species than an index obtained from plant weights in the growing crop.  相似文献   

10.
A weed monitoring conducted by Syngenta Agro GmbH in co-operation with the University of Hohenheim was carried out to evaluate the local and regional weed situation in maize in Germany. The fields were monitored at the two to six leaf stage of maize before weed control. A total of 2602 maize fields across Germany has been investigated from 2000 until 2004. Altogether 204 weed species (including volunteer crops) from 32 plant families have been recorded. The dicots were the predominant group with 166 species. The monocots were represented by 36 species and two species belonged to the family of Equisetaceae; volunteer crops were represented by 22 species. The most frequent species were Chenopodium spp. (79.7%) in particular Chenopodium album, followed by Stellaria media (61.0%), Fallopia convolvulus (55.7%), Echinochloa crus-galli (53.0%), Matricaria spp. (50.3%), Viola arvensis (47.8%), Polygonum aviculare (45.8%), Lamium spp. (41.6%), Galium aparine (39.7%) and Elytrigia repens (39.4%). The results demonstrate that with the exception of Echinochloa crus-galli, species usually considered for being typical for maize as e. g. Solanum nigrum, Amaranthus spp. and Galinsoga spp. are not dominating. Among the volunteer crops, rape was most abundant (17.2%). On average the weed density over all fields was 192 plants m-2. The monitoring clearly shows that some weeds occur predominantly in certain areas as e. g. Solanum nigrum and Stellaria media in the north-west and Veronica spp. in the south of Germany. Beside climatic conditions differences in cropping systems and cultivation practices lead to a specific weed flora in maize. In comparison to similar investigations in the seventies of the last century, some species species as e. g. Veronica spp. and Viola arvensis have increased dramatically. This increase is mainly due to the use of sulfonylurea herbicides which are weak on these species. The increase of Geranium spp., weeds which are rather new in maize, is also linked to the low efficacy of the herbicides presently used on these species. All the species found during the five years monitoring are presented by their frequency of occurrence.  相似文献   

11.
Dicotyledonous weeds of spring cereal crops in north-east Scotland   总被引：1，自引：0，他引：1  
A survey of dicotyledonous weeds of spring cereals was conducted prior to herbicide application in 1985 in six districts of north-east Scotland, which involved a total of 113 fields. Results were similar to those from an earlier survey in 1973. The main species remained the same but in four of the six districts, total weed densities were lower. Stellaria media was the most common species except in Upper Banffshire and Morayshire where Galeopsis spp. and Polygonum aviculare, respectively, were predominant. The main changes apparent were a decline of Spergula arvensis and Polygonum persicaria, and an increase in Matricaria perforata and Viola arvensis in several districts.  相似文献   

12.
We assessed the seed production and shedding pattern of 10 common weed species in two oat fields in Denmark. The aim was to evaluate the possibility of harvesting retained seeds on weeds at crop harvest by a combine harvester based on estimation of weed seed retention. Before flowering, ten plants of each weed species were selected and surrounded by a seed trap comprising of a porous net. When the plants started shedding seeds, the seeds were collected from the traps and counted weekly until oat harvest. Just before oat harvest, the retained seeds on the plants were counted and the ratio of harvestable seeds and shed seeds during the growing season was determined. The seed production and shedding patterns varied between the 2 years. Across both years, Anagallis arvensis L., Capsella bursa-pastoris L. Medik, Chenopodium album L., Geranium molle L., Persicaria maculosa Gray, Polygonum aviculare L., Silene noctiflora L., Sonchus arvensis L., Veronica persica Poir. and Viola arvensis Murray retained on average 61.6%, 52.7%, 67.2%, 58.4%, 32.05%, 59.5%, 95.7%, 23.5%, 51.7% and 33.9%, respectively, of their produced seeds at crop harvest. Silene noctiflora was classified as a good target for harvest weed seed control; C. bursa-pastoris, C. album, G. molle, P. maculosa, S. arvensis and V. arvensis were classified as intermediate targets; and A. arvensis, P. aviculare and V. persica were classified as poor targets.  相似文献   

13.
The objective of this research was to compare selected ecophysiological parameters for a wheat crop found in the Indo‐Gangetic Plains of India and its five dominant weeds. The dominant and regionally ubiquitous weeds in the wheat field that was selected for the study were Anagallis arvensis, Chenopodium album, Melilotus albus, Phalaris minor and Rumex dentatus. Taller weeds, such as C. album and P. minor, constituted one group along with the crop, with a low photosynthetic rate, specific leaf area, leaf nitrogen mass basis, chlorophyll content, photosynthetic nitrogen‐use efficiency and leaf area ratio, in comparison to shorter weeds, such as A. arvensis, M. albus and R. dentatus, which formed another group with a high photosynthetic rate, specific leaf area, leaf nitrogen mass basis, chlorophyll content, photosynthetic nitrogen‐use efficiency and leaf area ratio. Interspecific variations in the photosynthetic rate were driven mainly by variability in the specific leaf area and leaf nitrogen content. The taller weeds and the crop had a low specific leaf area later in the season, whereas the smaller weeds had a relatively high specific leaf area, which might be an adaptation to the shaded environment below the canopy. The result indicates that any weed management in the wheat fields of the Indo‐Gangetic Plains will need two different approaches because of the different strategies followed by the two weed groups that were identified in the present study.  相似文献   

14.
Commercial vineyards in southern Spain were surveyed and sampled during October to December 2004 to determine the extent to which common weeds present were suitable hosts of root-knot nematodes infesting soils of those vineyards. Seven weed species commonly growing in grapevine soils in southern Spain were found infected by either Meloidogyne incognita or M. javanica: Amaranthus retroflexus (redroot pigweed), Anchusa azurea (ox-tongue), Chenopodium album (goosefoot), Erodium moschatum (musk stork’s bill), Malva rotundifolia (low mallow), Sinapis alba (white mustard), and Solanum nigrum (black nightshade). The host suitability of the weeds to root-knot nematodes was evaluated on the basis of root galling severity and nematode population densities in soil and roots. Also, the host–parasite relationship in these naturally Meloidogyne-infected weeds was examined. All the weed species in the study were considered suitable hosts for M. incognita and M. javanica because: (a) high Meloidogyne spp. populations occurred in roots and surrounding soil of the weed species; (b) the severity of root galling was high, and (c) well-established permanent feeding sites were observed in the histopathological studies of infected root tissues. In addition, this study presents the first reports of S. alba and A. azurea as hosts for M. incognita, and of E. moschatum as a new host for M. javanica, thus increasing the list of reported weed hosts for Meloidogyne spp. These results indicate that noticeable population densities of M. incognita and M. javanica can be maintained or increased in these weeds, at population levels higher than those previously reported for the same nematodes infecting grapevine roots. The weeds infesting vineyards thus represent an important source of inoculum of Meloidogyne spp., and furthermore may act as reservoirs of these nematodes which can be disseminated within or among vineyards by agricultural operations.  相似文献   

15.
Data on weed species currently found in winter oilseed rape, the extent of their occurrence and regional distinctions were collected in autumn 2005 and 2006 from a total of 978 rape fields throughout Germany. Investigations took place on untreated sites at the six to eight leaf stage of rape. Weed frequencies and densities were determined by randomly placing a 0.1?m2 quadrate frame ten times in each plot, identifying and counting all plants within the frame. Two year results are presented here with a main focus on regional distinctions in total weed infestation, species richness as well as differences in frequencies and densities of selected weed species between the federal states. As expected, the majority of weed species occurring in winter oilseed rape is not evenly spread over Germany. On the on hand there are weeds with a more or less limited distribution which can be frequently found in some regions but are absent in others while on the other hand several ubiquitous weed species mainly show regional differences in their densities. Sisymbrium officinale, Descurainia sophia, Centaurea cyanus, Anchusa sp., Sonchus sp., Rumex sp. or Euphorbia sp. are some of the weed species of mostly regional importance. In contrast statistically proofed differences in weed densities in the federal states of Germany were recorded for Capsella bursa-pastoris, Chenopodium album, Galium aparine, Lamium sp., Matricaria sp., Stellaria media, Thlaspi arvense, Veronica sp. and Viola arvensis. Total weed infestation level and the mean number of species per site also differed between the federal states of Germany.  相似文献   

16.
The influence of weedy field strips on the abundance patterns of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and predatory bugs of Orius spp. (Hemiptera: Anthocoridae), on faba bean and on weeds was investigated in Adana province, Turkey, during 2005–2006. There were two treatments: in one treatment, weeds at the margins and inside the plots were regularly controlled by tillage; in the other treatment no weed control was done. Thrips and Orius were sampled by beating faba bean plants and weeds. Orius niger (Wolff) was the most abundant predatory insect species in faba bean and flowering weeds, with numbers of adults and nymphs significantly greater in plots with weedy margins than in weed-free plots. Flowering weeds did not contribute to the abundance of F. occidentalis on faba bean. Abundance of adults of Orius spp. did not coincide with the abundance of F. occidentalis on faba bean or weeds. There were significant negative associations for numbers of Orius spp. among faba bean and the weed species Lamium amplexicaule L. or Sinapis arvensis L. (P < 0.05), indicating movement of Orius individuals from the weeds to faba bean during March–April. Finally, faba bean and weeds may provide some benefits to predators, such as nectar, pollen, shelter and egg-laying sites rather than as sources of insect prey. Cultivation of faba bean could be useful for conservation and augmentation of beneficial insects, including Orius spp. Furthermore, field margins bearing flowering weeds such as S. arvensis and L amplexicaule should be protected against destructive management practices, because they host considerable numbers of the Orius species.  相似文献   

17.
Field experiments were conducted to study weed population shifts in long‐term conservation tillage systems. The objectives of this study were to determine weed community abundance, diversity and composition on conventional tillage (CT), minimum tillage (MT), no‐tillage with paraplow (ZT) and no‐tillage (NT) systems, and to identify species that are associated with specific tillage systems. The paraplow is a subsoiling technique that results in a deep loosening of the soil, in order to alleviate compaction in certain soils where NT is practiced. The results showed significant differences in both the composition and the abundance of weeds, depending on the tillage systems. Weed diversity, species richness and Shannon's diversity and evenness indices were higher under the conservation tillage systems than in the CT system. In addition, various weed species were associated with reduced tillage systems. For instance, Anthemis arvensis, Hirschfeldia incana and Lolium rigidum became more prevalent in the NT system, whereas Chenopodium album and Filago pyramidata dominated in the ZT system. Therefore, the application of a paraplow treatment changed the weed community in the NT system. Other weed species, such as Capsella bursa‐pastoris and Torilis nodosa, dominated in all three conservation tillage systems, whereas soil disturbance by mouldboard ploughing favoured species such as Polygonum aviculare and Phalaris paradoxa.  相似文献   

18.
In the present study we show for the first time the suitability of the laser-induced fluorescence technique to evaluate in vivo herbicide-induced damages as revealed by changes of fluorescence spectra and lifetime. Four herbicides of different modes of action (glyphosate, bromoxynil, mesotrione, and amitrole) were selected and applied to four weed species (Stellaria media, Setaria viridis, Chenopodium album, and Viola arvensis). Modifications of the fluorescence signature depended on the agrochemical – plant species interaction as well as on the time after application. Measurements in the red and far-red spectral region reveal disturbances in the functionality of the photosynthetic apparatus and chlorophyll concentration, e.g. after application of bromoxynil or mesotrione. Recordings in the blue and green spectral regions indicate changes of both amount and composition of specific fluorophores, i.e. after application of glyphosate and amitrole. In all spectral measurements, the position of peak maxima was not affected by herbicide application. The fluorescence lifetime, expressed as LTmean or as lifetime 1 (LT1, short-duration) and LT2 (long-duration) fractions, provided additional information to the spectrally resolved data. Thereby, significant alterations of the lifetime duration and fractional characteristics were observed at specific wavelengths, e.g. after application of bromoxynil, mesotrione, or amitrole.  相似文献   

19.
BACKGROUND: Typical active ingredient (AI) residue patterns are formed during droplet drying on plant surfaces owing to the interaction of spray solution characteristics and leaf micromorphology. Currently, comparatively little is known about the influence of AI deposit patterns within a spray droplet residue area on the penetration and biological efficacy of glyphosate. A scanning electron microscope with energy dispersive X‐ray microanalysis has been used to characterise residue patterns and to quantify the area ultimately covered by glyphosate within the droplet spread area. RESULTS: The easy‐to‐wet weed species Stellaria media L. and Viola arvensis L., as well as the difficult‐to‐wet Chenopodium album L. and Setaria viridis L., differing in their surface micromorphology, have been used. Rapeseed oil ethoxylates (RSO 5 or RSO 60) were added to glyphosate solutions to provide different droplet spread areas. Addition of RSO 5 enhanced droplet spread area more than RSO 60, and both caused distinct glyphosate residue patterns. The biological efficacy of treatment solutions showed no significant correlation with the area ultimately covered by glyphosate. CONCLUSION: The results have implications on herbicide uptake models. This study shows that droplet spread area does not correspond to the area ultimately covered by glyphosate, and that the latter does not affect glyphosate phytotoxicity. Copyright © 2009 Society of Chemical Industry  相似文献   

20.
Resistant annual and herbaceous perennial plant species were identified as key hosts which allow Phytophthora cinnamomi to persist on severely impacted black gravel sites within the Eucalyptus marginata (jarrah) forest of southwest Western Australia. Of the annual and herbaceous perennial plant species present on black gravel sites, 15 out of 19 species were found to be hosts of P. cinnamomi, and 10 of these were symptomless hosts. In particular, the native annual Trachymene pilosa and the two native herbaceous perennials Stylidium diuroides and Chamaescilla corymbosa were commonly found to be hosts of the pathogen. Species from 12 new genera including three from new families (Crassulaceae, Droseraceae and Primulaceae) are reported for the first time to be hosts of P. cinnamomi. The species from which P. cinnamomi was recovered were the native species: Chamaescilla corymbosa, Crassula closiana, Drosera erythrorhiza, Hydrocotyle callicarpa, Levenhookia pusilla, Paracaleana nigrita, Podotheca angustifolia, Pterochaeta paniculata, Rytidosperma caespitosum, Siloxerus multiflorus, Stylidium diuroides and Trachymene pilosa, and the introduced annual weeds Hypochaeris glabra, Lysimachia arvensis and Pentameris airoides.  相似文献   

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