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1.
Weed seeds are introduced to agronomic systems naturally or through human-mediated seed dispersal, and introduced seeds have a high chance of being resistant to selective, in-crop herbicides. However, colonisation (invasion) rates for a weed species are usually much lower than rates of seed dispersal. The current research investigated colonisation of a winter annual wheat cropping system in Western Australia by a range of winter or summer annual weed species. The weed seeds were sown (at 100 seeds/m2) directly before seeding the crop in 2016 and allowed to grow in the following 3 years of wheat. Selective herbicides were not applied, to simulate growth of weed populations if the initial seed had been resistant to herbicide. Bromus diandrus, Hordeum leporinum, Rumex hypogaeus, Sonchus oleraceus, Polygonum aviculare, Lolium rigidum, Citrullus amarus and Tribulus terrestris colonised the crop, while Dactyloctenium radulans, Chloris truncata and Salsola australis failed to establish over 3 years. The most successful weed was B. diandrus, with a plant density of 1,170/m2 by the third year and seed production of 67,740/m2. The high density of B. diandrus reduced wheat density by 76% in the third year and reduced average yield by 36%. Lolium rigidum reduced average yield by 11%, and the other weed species did not affect crop yield. Further research is required on the invasiveness of these species in other regions, but it is clear that the spread of B. diandrus to new areas or the introduction of resistant B. diandrus seeds via contaminated grain should be avoided.  相似文献   

2.
Development of integrated weed management strategies is dependent on a thorough knowledge of the demography of individual species. The current research established eight winter or summer weed species in a winter annual wheat cropping system at Wongan Hills, Western Australia, and investigated emergence of the first cohort of each species, survivorship, plant size, seed production and seed shedding over three years (2016–2019). The winter weeds Bromus diandrus and Lolium rigidum emerged at the same time as the wheat crop, and the initial cohort of marked plants had 100% survival to seed production in each year. By comparison, other winter weed species like Hordeum leporinum, Rumex hypogaeus, Sonchus oleraceus and Polygonum aviculare frequently emerged later than the crop and had a lower percentage of plants surviving to seed production. However, individual S. oleraceus and P. aviculare plants had the greatest seed production compared to other species. All winter weeds had variable patterns of seed shedding between years, with the exception of L. rigidum. Summer weed species emerged at the same time, but plants in the initial cohort of each species did not always survive to produce seed. The early emergence and high survivorship of B. diandrus indicates high competitive ability, but shedding commenced at a similar time to L. rigidum and harvest weed seed control may be a viable control method for this species.  相似文献   

3.
Estimation of thresholds for weed control in Australian cereals   总被引：1，自引：0，他引：1  
A non-linear model relating crop yield to the density of weeds was fitted to nine Victorian weeds to evaluate their competitive abilities. The weeds were: Acroptilon repens (L.) DC. (creeping knapweed), Chondrilla juncea L. (Skeleton weed, Raphanus raphanistrum L. (Wild radish), lolium rigidum Gaud. (Annual ryegrass), Lithospermum arvense L. (White iron weed), Brassica tournefortii Gouan (Wild turnip), Lamium amplexicaule L. (Deadnettle), Fumaria parviflora Lam. (White fumitory) and Amsinckia hispida (Ruiz & Pav.) I.M. Johnston (Amsinckia). Where more than one experiment was available for a weed, the net return for a herbicide treatment over a range of weed densities was calculated to obtain the economic threshold density. Generally, the economic threshold densities within a weed species were the same order of magnitude, except for the perennial Chondrilla Juncea L., For this species data were collected in years of contrasting rainfall. The model used here is discussed in view of the threshold approach currently used in continental Europe.  相似文献   

4.
Hordeum spp. (barley grass) and Bromus spp. (brome grass) are annual weed species that achieve long-distance seed dispersal via attachment to sheep, but also lead to sheep carcass damage due to the penetration of seeds into animal tissues. Range expansion of invasive weed populations predicted as a consequence of climate change may be associated with an increase in seed contamination incidence globally. An examination of Australian abattoir data (2006–2012), along with recent weed distribution patterns, indicates carcass contamination was associated with rainfall and abundance of key annual grass weeds, primarily Bromus spp. and Hordeum spp., although other factors may play a contributing role. Significant differences in seed contamination in slaughtered sheep were noted between states and regions, with widespread contamination occurring throughout all agro-ecological zones. Abattoir, sheep age and sex significantly influenced incidence, with contamination highest in adult males. Incidence increased with mean monthly rainfall, but declined with mean elevation, and significant interactions were noted between mean monthly temperature and state, and between mean elevation and year. Results show the need for vigilant recording of seed injuries in sheep to enhance weed surveillance efforts and effective integrated weed management of contributing annual grass weeds.  相似文献   

5.
Intensification of agricultural practices has severely reduced weed diversity in arable fields, which affects the delivery of ecosystem services. However, in parallel, some species have benefited from intensive farming and have vastly increased their abundance, as is the case for Lolium rigidum and Avena sterilis in cereal fields. These highly competitive species severely reduce yields but can also compete with other weed species, and, when less intensive practices are applied, they might limit the recovery of weed diversity and the success of arable species reintroductions. A gradient of infestation was established in a winter wheat field in Catalonia (north‐eastern Spain) by sowing seeds of both species at three different densities to test their effects on the abundance, diversity and composition of the natural weed community. The emergence of seeds and the survival and biomass of transplanted seedlings of two rare species, Agrostemma githago and Vaccaria hispanica, were also evaluated. Avena sterilis and L. rigidum infestations reduced the diversity, abundance and biomass and changed the composition of the natural weed community, even at low infestation densities. Moreover, infestations of both species affected the overall performance of A. githago and V. hispanica. This study reveals that A. sterilis and L. rigidum are highly competitive and that their infestations might hamper the recovery of diverse weed communities. Their densities should be considered when selecting suitable sites for promoting diversity and reintroducing rare species.  相似文献   

6.
Solanum elaeagnifolium is a weed of national significance in Australia. However, the genetic diversity of S. elaeagnifolium is poorly understood. Four amplified fragment length polymorphism primer combinations were utilised to investigate the genetic variation and structure of 187 S. elaeagnifolium individuals collected from 94 locations in Australia. High genetic diversity was found, with an average Jaccard's genetic similarity at 0.26. Individuals were assigned to two genetic clusters or considered as admixed according to their membership coefficient value (q) calculated by Bayesian model‐based genetic structure analysis. This suggested that Australian S. elaeagnifolium may have originated from two distinct gene pools. These results were further supported by principal co‐ordinates analysis. Large spatial groups of individuals assigning to these two gene pools were found in western Victoria and south‐western New South Wales (NSW) and northern NSW, which correlated well with the early records of S. elaeagnifolium in both regions. The high genetic diversity found here could add difficulties to effective control of S. elaeagnifolium across regions.  相似文献   

7.
Chenopodium album became a problem weed in sugar beet production, due to resistance to metamitron, a key herbicide in this crop. Dispersal of the seeds from resistant biotypes may occur due to spread by wind, animals, agricultural machinery or manure. This study examined the effect of ensiling, digestion by cattle and storage in slurry and farmyard manure on the germination and viability of the seeds of one susceptible and three resistant C. album populations. After 4 weeks in a maize silo, seed viability of C. album populations was reduced drastically to 0–5%. Incubation for 24 h in the rumen followed by a post‐ruminal digestion in vitro of intact seeds only resulted in a small reduction in viability in one C. album population. Storage in a slurry cellar for 16 weeks reduced the viability of intact seeds of the C. album populations to 25–60%. Only 0–1% of the seeds remained viable after storage in a farmyard manure heap for 4 weeks. An accelerated ageing experiment showed seed persistence to be population specific and less related to seed weight. Keeping a fresh maize silo closed for at least 4 weeks and heaping farmyard manure are excellent preventive measures to limit the spread of resistant C. album seeds between fields.  相似文献   

8.
Solanum elaeagnifolium (silverleaf nightshade) is a problematic weed that is common in Jordan and difficult to control. The weed exhibits distinct morphological variations in growth habit, leaf shape, leaf margins, flower colour and presence or absence of spines between individuals among and within populations suggesting genetic differences. Genetic variations among 61 samples of S. elaeagnifolium collected from heavily infested sites in the central Jordan Valley were investigated using six simple sequence repeat (SSR) markers and eight amplified fragment length polymorphism (AFLP) primer combinations. Results showed that 111 out of 675 AFLP bands were polymorphic generating polymorphism information content (PIC) of 38.0%, while 23 SSR polymorphic alleles were detected generating a PIC of 30.8%. Phylogenetic analysis using RaxML software identified four major clades with a clear clustering of the samples with their collection sites. Genetic analysis using both techniques revealed high level of genetic diversity among S. elaeagnifolium samples collected from a small geographical area indicating that a range of genetic diversity may be detected in weed populations across the country that may complicate its management.  相似文献   

9.
The aim of this study was to determine the effect of soil solarization on soilborne diseases, weeds and plant yields by using polyethylene film (30-μm-thick) containing different additives [ultraviolet (UV), ultraviolet + infrared (UV + IR), ultraviolet + infrared + anti-fog + anti-dust (UV + IR + AF + AD)], and used polyethylene film (260-μm-thick). Trials were conducted in commercial strawberry (Fragaria ananassa cv. ‘Camarosa’) fields in the town of Sultanhisar in Aydin province, Turkey, between 2007 and 2009. The highest soil temperatures at the depth of 10 cm under a polyethylene sheet containing UV + IR + AF + AD were 54°C in 2007 and 50.7°C in 2008. During the 2007 growing season, collapse and death of strawberry plants were not detected. At the end of the 2008 season (May–June), collapsed and dying strawberry plants were observed. Pure cultures of Macrophomina phaseolina and Rhizoctonia solani were isolated from affected roots and crowns of plants. Viability studies of M. phaseolina were conducted under various field conditions and temperatures and M. phaseolina sclerotia survived more than 18 days at 45°C. There was a sharp decline in M. phaseolina at 50°C, where it survived for 19 h but was completely killed at 20 h. It first lost viability after 17 h at 50°C and after 60 min at 55°C. In the field, solarization did not reduce the viability of M. phaseolina at a soil depth of 10 or 20 cm; however, a significant reduction (66%) in survival was determined at a soil depth of 5 cm. All treatments controlled Portulaca oleracea, Amaranthus spp., Digitaria sanguinalis, Echinochloa crus-galli, Veronica hederifolia, Raphanus raphanistrum, Setaria verticillata and Mercurialis annua at a rate of 100%, but no treatment was effective on Cyperus rotundus. The marketable fruit yield was 38,004 kg.ha−1 for UV + IR, 35,834 kg.ha−1 for UV-added polyethylene film and 35,368 kg.ha−1 for used polyethylene sheet-covered plots, whereas it was 27,365 kg.ha−1 for untreated control plots.  相似文献   

10.
Lolium rigidum (annual or rigid ryegrass) is a widespread annual weed in cropping systems of southern Australia, and herbicide resistance in L. rigidum is a common problem in this region. In 2010, a random survey was conducted across the grain belt of Western Australia to determine the frequency of herbicide‐resistant L. rigidum populations and to compare this with the results of previous surveys in 1998 and 2003. During the survey, 466 cropping fields were visited, with a total of 362 L. rigidum populations collected. Screening of these populations with the herbicides commonly used for control of L. rigidum revealed that resistance to the ACCase‐ and ALS‐inhibiting herbicides was common, with 96% of populations having plants resistant to the ACCase herbicide diclofop‐methyl and 98% having plants resistant to the ALS herbicide sulfometuron. Resistance to another ACCase herbicide, clethodim, is increasing, with 65% of populations now containing resistant plants. Resistance to other herbicide modes of action was significantly lower, with 27% of populations containing plants with resistance to the pre‐emergent herbicide trifluralin, and glyphosate, atrazine and paraquat providing good control of most of the populations screened in this survey. Ninety five per cent of L. rigidum populations contained plants with resistance to at least two herbicide modes of action. These results demonstrate that resistance levels have increased dramatically for the ACCase‐ and ALS‐inhibiting herbicides since the last survey in 2003 (>95% vs. 70–90%); therefore, the use of a wide range of integrated weed management options are required to sustain these cropping systems in the future.  相似文献   

11.
The phyllosphere and rhizosphere of weeds are important niches for phytobacterial survival. The absence of information in Brazil regarding Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot in crucifers, motivated this study. Twenty‐six weed species belonging to 14 botanical families were included in field experiments between August 2014 and October 2015. Lepidium virginicum and Raphanus raphanistrum (Brassicaceae) demonstrated great potential for survival of Xcc in the phyllosphere, with the bacterium isolated after 56 and 70 days, respectively. Low variation between maximum and minimum temperatures, high rainfall and high relative humidity at specific times of the year contributed to longer Xcc survival periods in the phyllosphere of some species. Xcc survived in the rhizosphere only in R. raphanistrum, where it was isolated for up to 28 days. No relation was found between climatic factors and survival in the rhizosphere. The data indicate that control of brassicaceous weeds will contribute to the control of black rot.  相似文献   

12.
Pseudocercosporella capsellae (white leaf spot disease) is an important disease on crucifers. Fifty‐four single‐conidial isolates collected from Brassica juncea (Indian mustard), B. napus (oilseed rape), B. rapa (turnip), and Raphanus raphanistrum (wild radish) across Western Australia were investigated for differences in pathogenicity and virulence using cotyledon screening tests, genetic differences using internal transcribed spacer (ITS) sequencing and phylogenetic analysis, and growth rates on potato dextrose, V8 juice and malt extract agars. All isolates from the four crucifer hosts were pathogenic on the three test species: B. juncea, B. napus and R. raphanistrum, but showed differences in levels of virulence. Overall, isolates from B. juncea, B. napus and B. rapa showed greatest virulence on B. juncea, least on R. raphanistrum and intermediate virulence on B. napus. Isolates from R. raphanistrum showed greatest virulence on B. juncea, least on B. napus and intermediate virulence on R. raphanistrum. Growth and production of a purple‐pink pigment indicative of cercosporin was greatest on malt extract agar and cercosporin production on V8 juice agar was positively correlated with virulence of isolates on B. juncea and B. napus. ITS sequencing and phylogenetic analysis showed that isolates collected from B. napus, B. juncea and B. rapa, in general and with few exceptions, had a high degree of genetic similarity. In contrast, isolates from R. raphanistrum were clearly differentiated from isolate groups collected from Brassica hosts. Pseudocercosporella capsellae reference isolates from other countries generally grouped into a single separate cluster, highlighting the genetic distinctiveness of Western Australian isolates.  相似文献   

13.
As herbicides have limited effect in controlling Bromus diandrus in no‐till dryland cereal fields, the integration of chemical and cultural methods needs to be investigated. A field study was carried out in Lleida (Spain) during 2008–09, 2009–10 and 2010–11 seasons, in a no‐till winter cereal field integrating delayed crop sowing with herbicides in a barley–wheat–wheat rotation. Three crop sowing dates were considered: D1, mid‐October; D2, mid‐November; and D3, early December, and the herbicides mesosulfuron‐methyl plus iodosulfuron‐methyl‐sodium were applied in wheat. Weed density, cumulative emergence and fecundity were estimated for each sowing date. In all three seasons, a significant reduction in the cumulative emergence of B. diandrus as compared to D1 was observed in D2 (82.0, 97.5 and 98.1%) and D3 (80.8, 98.7 and 97.2%). In addition, a significant decrease in weed density and seed rain was observed across all sowing dates and seasons. The herbicide used in wheat was more effective under delayed sowing, due to lower weed density and presence of less developed weed seedlings. After three seasons, the populations of B. diandrus were completely depleted in D2 and D3. This study demonstrates the possibility of eliminating brome infestations in dryland cereal fields in no‐till systems through the integration of cultural and chemical strategies.  相似文献   

14.
A few years ago, a new invasive weed was found in Spanish maize fields grazed by sheep after harvest and identified as a subform of teosinte (Zea mays ssp. mexicana ad int). If teosinte seeds survive digestion, then the weed could spread via sheep manure. The aim of this study was to assess the effect of this process on the emergence and viability of teosinte seeds. In an in sacco study, seeds were introduced into the rumen of fistulised wethers and extracted after 24, 48, 72 and 96 h. Then, seed emergence was recorded and the viability of non‐germinated seeds was analysed. In an ‘intake and in vivo’ study, lambs were kept in metabolic cages and fed for 6 days with 200 g teosinte seeds and ears. The daily faecal production was individually collected, seeds were recovered and viability was tested (15 days). In the in sacco trials, a decrease in teosinte viability was observed after remaining for 48 h or more in the rumen. In the ‘intake and in vivo’ trial, between 0.1% and 3% of the ingested seeds that were excreted were viable. Uncoated seeds that lost their exocarp during the mastication and digestion processes were less viable (18%) than intact excreted seeds (74%). The last viable and intact seeds appeared 4 and 6 days after intake respectively. In areas with teosinte infestation, sheep grazing on maize stubble should be avoided and, in case of ingestion, sheep should be kept isolated for 4–6 days to avoid the spread of this invasive weed.  相似文献   

15.
Cultivated plants are known to readily hybridise with their wild relatives, sometimes forming populations with weedier life‐history strategies than their progenitors. Due to altered precipitation patterns from human‐induced global climate change, crop‐wild hybrid populations may have new and unpredictable environmental tolerances relative to parental populations, which would further challenge farming and land‐management weed control strategies. To recognise the role of seed dormancy variation in weed invasion, we compared seedbank dynamics of two cross‐type populations (wild radish, Raphanus raphanistrum, and crop‐wild hybrid radish, R. raphanistrum × R. sativus) across a soil moisture gradient. In a seed‐burial experiment, we assessed relative rates of seed germination, dormancy and seed mortality over two years across cross types (crop‐wild hybrid or wild) and watering treatments (where water was withheld, equal to annual rainfall, or double annual rainfall). Weekly population censuses in 2012 and 2013 assessed the frequency and timing of seedling emergence within a growing season. Generally, germination rates were two times higher and seed dormancy was 58% lower in hybrid versus wild populations. Surprisingly, experimental soil moisture conditions did not determine seedbank dynamics over time. Yet, seed bank dynamics changed between years, potentially related to different amounts of annual rainfall. Thus, variation in seedbank dynamics may be driven by crop‐wild hybridisation rates and, potentially, annual variation in soil moisture conditions.  相似文献   

16.
Silverleaf nightshade (Solanum elaeagnifolium, Cav.) is one of the important invasive plant species in Mediterranean Basin countries. Over the last 60 years, this plant has gone from a few accidental introductions to near monospecific populations in many areas of the Mediterranean Basin (in particular Greece and Morocco). Recent findings from Lebanon show that the invasion is ongoing. Solanum elaeagnifolium has a negative impact on crops, causing up to 75% yield loss, as well as an indirect impact by harbouring plant pests and diseases. Solanum elaeagnifolium is toxic to livestock and has a negative affect on the quality of life for humans. Losses of potential resource or revenue caused by its invasion include: decreased forage quality on grazing lands; decreased cropping land and amenity values of public space; increased water loss; increased water conveyancing costs; and increased forest restoration costs. Available control techniques need to be strengthened to reduce the impact of S. elaeagnifolium and prevent its spread. More attention needs to be devoted to biological control, which could provide regional management of this invasive alien plant. Sustainable management of S. elaeagnifolium will require coordination, education and support across the affected countries. Governments must have the means to detect, manage and control S. elaeagnifolium.  相似文献   

17.
In the context of an epidemiological study on Potato virus Y (PVY) in potato crops, Solanum elaeagnifolium Cav. was included in the weeds prospected. Surveys were carried out in four seed potato areas: Cap Bon, Manouba, Jendouba and Kairouan. S. elaeagnifolium was found in all areas, except Cap Bon. Virus‐like symptoms were observed on some S. elaeagnifolium plants in the field, i.e. leaf mottling and curling. Aphids were collected on these plants and were identified as Myzus persicae and Aphis fabae, both known to colonize potatoes and to transmit the standard PVYN isolate with transmission efficiencies of 95% and 43%, respectively. Forty‐seven plant samples were tested with ELISA for the presence of PVY. Positive reactions were obtained from 2/6, 5/18, 8/23 samples collected in Manouba, Jendouba and Kairouan, respectively. Virus transmission was carried out using M. persicae as vector from two samples of each region onto plantlets of Nicotiana tabacum cv Xanthi. All inoculated plantlets displayed typical symptoms of the PVYN strain group, confirmed by serological testing using specific antibodies. This is the first report of a PVY natural infection on S. elaeagnifolium in Tunisia. The abundance of this weed, its over‐wintering status and the high rate of PVY‐infected plants (31.9%) allow us to deduce that S. elaeagnifolium must be considered a reservoir species of PVY under natural conditions in Tunisia and probably in other Mediterranean countries. The presence of efficient aphid vectors of PVY on this weed in crops is additional evidence that S. elaeagnifolium may become a problem by acting as a source plant for PVY spread in potato crops.  相似文献   

18.
The adoption of no‐tillage systems in semi‐arid cereal fields in northern Europe has resulted in difficulties in controlling Bromus diandrus. However, in some fields, lower densities are observed in continuous long‐term no‐tillage management than in other reduced tillage systems. A cumulative effect on the seedbank could promote changes in the period of seedling emergence and in population demography. This study evaluated the effect of long‐term mouldboard plough (MbP), chisel plough (ChP), subsoiler (SS) and no‐tillage (NT) on the population dynamics of B. diandrus. The work was carried out in a barley (Hordeum vulgare)–wheat (Triticum aestivum)–barley rotation during three seasons where these soil management systems had been applied for the last 22 years. Cumulative emergence (CE) and densities of B. diandrus followed a gradient of ChP > SS > NT > MbP. This cumulative effect over time resulted in significant differences in population demography. A previous hydrothermal emergence model developed for this species estimated the percentage of emergence prior to the date of sowing to be: 71%, 92% and 53% for the seasons 2008–2009, 2009–2010 and 2010–2011 respectively. Furthermore, the reduction in CE observed was on average 53% in SS, 92% in NT and 98% in MbP in comparison with that recorded in ChP. The long‐term effect of different tillage systems tended to cause changes to soil characteristics (photo‐inhibition of germination, soil temperature, water availability) affecting B. diandrus demography, reaching equilibrium in weed densities over years, which were significantly lower in MbP and NT than in ChP or SS.  相似文献   

19.
Lolium rigidum Gaud. is an important weed of winter crops in some countries with Mediterranean-type climates. This paper reviews L. rigidum competition in wheat, factors influencing populations of this weed and the effect of control of L. rigidum numbers on wheat yields.  相似文献   

20.
M. Mekki 《EPPO Bulletin》2007,37(1):114-118
Silverleaf nightshade, Solanum elaeagnifolium, is listed as a noxious weed in its native range (Americas) and as an invasive alien plant in many countries across the world. Its local pattern of distribution in the EPPO region indicates that it is still in an establishment phase. S. elaeagnifolium invasiveness could be related to several biological traits: copious production of sexual and asexual propagules, its facility for long‐distance dispersion, its ability to endure considerable drought and to dominate shallow‐rooted vegetation, especially during summer dry periods, and its capacity to suppress more valuable species because it is unpalatable and toxic to cattle. Invasion of the Mediterranean semi‐arid region by S. elaeagnifolium was mainly facilitated by irrigation and animal production. Low moisture stress may favour this invasive species and sheep are an important pathway for its long‐distance dispersal. Once established, it is one of the most difficult weeds to eradicate because of its network of creeping horizontal and deep vertical roots. Its phenotypic plasticity enables it to adopt a rosette‐like growth pattern to escape control by repeated slashing. Thus, S. elaeagnifolium monitoring in the EPPO region is vital in order to contain established populations and prevent invasion.  相似文献   

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