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1.
The effects of three different weed management strategies on the required input of hand weeding in an arable organic farming system, the weed seedbank in the soil and the emerging weed seedling emergence were studied from 1996 to 2003. Strategies were based on population dynamic models and aimed for (1) control of weeds as carried out in standard organic farming practice, (2) control of all residual weeds that grow above the crop and (3) prevention of all weed seed return to the soil. Under all strategies, the size of the seedbank increased during the conversion from conventional to organic farming systems. The increase under strategy 3 was significantly smaller than the increase under the other strategies. From 1999 onwards, the weed densities in plots treated with strategy 3 became significantly lower than the weed densities in plots treated with the other strategies. The time needed for hand‐weeding required to prevent weed seed return, in addition to the time needed in standard organic farming practices, reduced during the course of the study. A management strategy aimed at the prevention of seed return (strategy 3) can reduce the size of the increase of the seedbank, which is usually observed after transition from conventional to organic farming. This study provides unique real‐world data that are essential for evaluating population dynamic models. The results may contribute to the development of weed management systems based on ‘no seed’ threshold strategies and to a further decrease in the dependence on herbicides. 相似文献
2.
Seed degeneration in potato: the need for an integrated seed health strategy to mitigate the problem in developing countries 
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下载免费PDF全文 S. Thomas‐Sharma A. Abdurahman S. Ali J. L. Andrade‐Piedra S. Bao A. O. Charkowski D. Crook M. Kadian P. Kromann P. C. Struik L. Torrance K. A. Garrett G. A. Forbes 《Plant pathology》2016,65(1):3-16
Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long‐standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and frequent use of seed, produced by specialized growers, that has been certified to have pathogen and pest incidence below established thresholds, often referred to as certified seed. The success of certified seed in developed countries has concentrated the research and development agenda on the establishment of similar systems in developing countries. Despite these efforts, certified seed has had little penetration into the informal seed systems currently in place in most developing countries. Small‐scale farmers in these countries continue to plant seed tubers acquired through the informal seed system, i.e. produced on‐farm or acquired from neighbours or local markets. Informal seed tubers frequently have poor health status, leading to significant reductions in yield and/or market value. This review emphasizes the need to refocus management efforts in developing countries on improving the health status of seed tubers in the informal system by integrating disease resistance and on‐farm management tools with strategic seed replacement. This ‘integrated seed health strategy’ can also prolong the good health status of plants derived from certified seed, which would otherwise be diminished due to potential rapid infection from neighbouring fields. Knowledge gaps, development challenges and impacts of this integrated seed health strategy are discussed. 相似文献
3.
Morrison RH 《Phytopathology》1999,89(11):1084-1087
ABSTRACT Seed health tests are usually performed on a sample of a seed lot; therefore, it is crucial that the test sample be as homogeneous as possible and representative of the lot. Seed sampling procedures appropriate for seed health testing have been developed by seed testing organizations such as the International Seed Testing Association and the Association of Official Seed Analysts. Seed lot size is generally not a constraint when the distribution of contaminated/infected seed in the lot is relatively homogeneous; if the distribution is heterogeneous, increased sampling intensity is required. Sample size is determined by the damage threshold (intolerable infection level) for the pathogen and the probability of detection desired, commonly 95 or 99%. The probability of detection at a given damage threshold is greater as sample size increases, and this probability and the appropriate sample size can be determined by statistical methods. Most seed health tests utilize qualitative data based on the presence or absence of the pathogen in the test sample, with the lot being rejected if the pathogen is detected in the sample and accepted if the sample is negative. 相似文献
4.
The effects of powdery mildew (caused by Sphaerotheca fuliginea )on muskmelon seedlings and the efficacy of seed treatment with systemic fungicides were examined under controlled environmental conditions. The fresh weight of seedlings infected with powdery mildew was substantially less than that of uninoculated seedlings 5 weeks after inoculation, and the inoculated seedlings shrivelled 1 week later. The fungicides fenarimol and triadimenol applied to the seeds did not affect germination and suppressed powdery mildew effectively when applied at a rate equivalent to 8 g fungicide product per kg seed. Under conditions moderately conducive to the pathogen, fenarimol markedly reduced disease severity and its effect when applied as a seed treatment was as effective as foliar treatment. When conditions were highly conducive to the pathogen, seed treatment with fenarimol was not effective. Development of powdery mildew and efficacy of the seed treatments were related to soil type: disease developed earlier and more intensely on seedlings grown in sandy soil than those in organic medium, and seed treatment had a more pronounced effect on seedlings grown in sandy soil. The results indicate that fungicidal treatment of muskmelon seeds may offer an adequate means of reducing powdery mildew infections on seedlings. 相似文献
5.
选取黄土高原5个地区杜松(Juniperus rigida)种子,采用种子萌发实验及相关分析的方法,研究其大小特征、萌发特性及其与生态因子的相关性,以了解不同地区杜松的种子萌发特性。结果表明,不同地区杜松的种子大小差异显著,府谷地区的种子最大、最重,平均长6.83 mm,宽3.56 mm,千粒重为25.89 g;种子长及种子长宽比随纬度的升高、土壤全磷含量的增加而变小;种子千粒重随1月和7月均温的增加而增加,随土壤有机质、速效磷、全氮含量的增加而减少。种子大小对萌发特征影响显著,种子萌发率、萌发势及发芽指数均随种子长、种子长宽比的增加呈减小的趋势。不同地区杜松的萌发差异显著,武川的种子萌发最快最高,府谷与贺兰山最慢、最低;萌发率、萌发势及发芽指数均随纬度的升高而增加,萌发势和发芽指数随土壤全磷含量的增加而增加。研究认为武川及浑源地区是杜松优良的选种地。 相似文献
6.
KRISTIN S.B. HARBUCK FABIAN D. MENALLED FREDRIC W. POLLNAC 《Weed Biology and Management》2009,9(2):160-168
Very little research has been done on weed seedbank communities in the northern Great Plains region of the USA. The objectives of this study were to evaluate the effects of management systems on the weed seed banks and to assess the relationship between the weed seed banks and the above-ground weed communities. The seed banks were sampled along a range of areas of above-ground weed diversity in organic and conventional spring wheat production fields near Big Sandy, Montana, over 2 years. Eight 1 m × 0.33 m areas were selected in each field to encompass a wide range of above-ground weed diversity and soil cores were taken in each area to a depth of 20 cm and split in half at 10 cm. The number of seeds recovered from the top 10 cm of soil and the 10–20 cm depth were significantly affected by the sampling year and an interaction between the cropping system and the sampling year. The year was the only significant predictor affecting the weed seedbank diversity at both depths. A significant interaction between the management system and the year observed at the 10–20 cm sampling depth reflected the higher rate of decrease in diversity occurring between 2005 and 2006 in the conventionally managed fields compared with the organic fields. A multivariate ordination indicated that, although the year played a significant role in determining the weed seedbank communities, the management system had a role only during 2006. We failed to detect strong correlations between the above-ground and underground weed communities. The results of this study suggest that, in the studied region, yearly fluctuations in environmental factors have significant impacts on the weed seed banks. 相似文献
7.
Abstract The mango seed weevil, Sternochetus mangiferae (Fabricius), is one of the major mango insect pests in northern Australia. A reasonable level of control can be obtained with insecticide sprays together with orchard sanitation, but the only option available for organic growers is the latter. Weaver ants, Oecophylla smaragdina (Fabricius), are effective in controlling the main insect pests in citrus, cashew and mango orchards. To determine whether weaver ants, which are usually abundant in non-sprayed mango orchards, have the potential to control the mango seed weevil, field experiments together with regular monitoring programmes at six orchards in the Northern Territory of Australia were conducted from 2001 to 2003. Data from two conventional orchards showed that the treatment with weaver ants plus soft chemicals produced lower levels of downgraded fruits (<0.5%) compared to the treatment with chemical insecticides (1.4 – 2.1%). In three organic or insecticide-free orchards, fruits were much less damaged on trees with weaver ants (<1%) than on trees without the ants (2.5 – 15.7%). In the sixth orchard, that had much higher mango seed weevil populations than the others, levels of downgraded fruits were lower on trees with abundant weaver ants than on trees with fewer weaver ants. We conclude that weaver ants are efficient biocontrol agents of the mango seed weevil, and that for successful control of the pest it is important both to maintain the ants at high levels and to destroy excess fruits. 相似文献
8.
J. Köhl C. A. M. Van Tongeren B. H. Groenenboom‐de Haas R. A. Van Hoof R. Driessen L. Van Der Heijden 《Plant pathology》2010,59(2):358-367
In organic seed production of Brassica vegetables, infections by Alternaria brassicicola and A. brassicae can cause severe losses of yield and seed quality. Four field experiments with or without artificial inoculation with A. brassicicola were conducted in organically managed seed‐production crops of cauliflower cv. Opaal RZ in 2005 and 2006 in the Netherlands. The development of A. brassicicola and A. brassicae on pod tissues and developing seeds was followed and seed quality was assessed. Alternaria brassicicola was externally present on 1·2% of the seeds 14 days after flowering and observed internally within 4 weeks after flowering. In both seasons, seed colonization by the pathogen increased slowly until maturation but sharply increased during maturation. A similar pattern was found for the colonization of pod tissues by A. brassicicola as quantified by TaqMan‐PCR. The incidence of A. brassicicola on mature seeds reached 70–90%. Internal colonization was found for 62–80% of the seeds. External and internal seed colonization by A. brassicae was much lower, with incidences below 3%. The quality of harvested seeds was generally low, with less than 80% of seeds able to germinate. Seed quality was not affected by warm water treatments. It was concluded that A. brassicicola and A. brassicae have the potential to infect pods and seeds soon after flowering. For the production of high quality seeds, producers must prevent such early infections. Therefore, new control measures are needed for use in organic cropping systems. 相似文献
9.
Michael Fürnkranz Eveline Adam Henry Müller Martin Grube Herbert Huss Johanna Winkler Gabriele Berg 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(3):509-519
Substantial yield losses of Styrian oil pumpkin caused by the fungus Didymella bryoniae and bacterial pathogens were recently reported. Here we applied bacterial endophytes with a broad antagonistic activity to pumpkin plants by seed priming. Effects of the bacterial inoculants with and without chemical seed treatments on plant growth and health were evaluated during three different field trials in two consecutive years (2010 and 2011). Biological seed treatments strongly supported the germination of pumpkin seeds. In 2010, the germination of the biologically treated seeds was comparable to the rate following a chemical treatment; whilst in 2011 effects of biological seed treatments were more obvious, including an increased emergence rate up to 109?% by Serratia plymuthica S13. Furthermore, tolerance against desiccation stress was observed for Serratia as well as for Lysobacter gummosus L101 treatment. The biological treatment showed different effects against fungal diseases: no effect on fruit rot was observed, whereas powdery mildew could be significantly suppressed by Paenibacillus polymyxa PB71 and L. gummosus L101 in 2010. In addition, both strains led to reproducible increases in harvest yields. In this study, we found bacterial endophytes suitable as inoculants for plant growth promotion, biocontrol, as well as for enhancing stress tolerance in Styrian oil pumpkins. 相似文献
10.
The implications of spatially variable pre‐emergence herbicide efficacy for weed management 下载免费PDF全文
下载免费PDF全文 Helen Metcalfe Alice E Milne Richard Hull Alistair J Murdoch Jonathan Storkey 《Pest management science》2018,74(3):755-765
BACKGROUND
The efficacy of pre‐emergence herbicides within fields is spatially variable as a consequence of soil heterogeneity. We quantified the effect of soil organic matter on the efficacy of two pre‐emergence herbicides, flufenacet and pendimethalin, against Alopecurus myosuroides and investigated the implications of variation in organic matter for weed management using a crop–weed competition model.RESULTS
Soil organic matter played a critical role in determining the level of control achieved. The high organic matter soil had more surviving weeds with higher biomass than the low organic matter soil. In the absence of competition, surviving plants recovered to produce the same amount of seed as if no herbicide had been applied. The competition model predicted that weeds surviving pre‐emergence herbicides could compensate for sublethal effects even when competing with the crop. The ED50 (median effective dose) was higher for weed seed production than seedling mortality or biomass. This difference was greatest on high organic matter soil.CONCLUSION
These results show that the application rate of herbicides should be adjusted to account for within‐field variation in soil organic matter. The results from the modelling emphasised the importance of crop competition in limiting the capacity of weeds surviving pre‐emergence herbicides to compensate and replenish the seedbank. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献11.
BACKGROUND: Aphis glycines Matsumura, an invasive insect pest in North American soybeans, is fed upon by a key biological control agent, Harmonia axyridis Pallas. Although biological control is preferentially relied upon to suppress insect pests in organic agriculture, approved insecticides, such as neem, are periodically utilized to reduce damaging pest populations. The authors evaluated direct spray treatments of two neem formulations, azadirachtin and neem seed oil, under controlled conditions for effects on survivorship, development time and fecundity in A. glycines and H. axyridis. RESULTS: Both azadirachtin and neem seed oil significantly increased aphid nymphal mortality (80 and 77% respectively) while significantly increasing development time of those surviving to adulthood. First-instar H. axyridis survival to adulthood was also significantly reduced by both neem formulations, while only azadirachtin reduced third-instar survivorship. Azadirachtin increased H. axyridis development time to adult when applied to both instars, while neem oil only increased time to adult when applied to first instar. Neither neem formulation affected the fecundity of either insect. CONCLUSIONS: Results are discussed within the context of future laboratory and field studies aimed at clarifying if neem-derived insecticides can be effectively integrated with biological control for soybean aphid management in organic soybeans. 相似文献
12.
Competition between winter barley and Avena sterilis is expected to depend on the specific conditions present in a given site. Considering that site conditions may be variable within a field, we hypothesised that the lower densities of A. sterilis frequently observed under more favourable soil conditions can be attributed to the improved growth and competitiveness of the barley crop under those conditions. Artificial populations of A. sterilis were established at three sites with different soil properties, both in the absence and the presence of a barley crop. Plant density, total biomass, dry weight per plant, seed production and seed per plant production were measured at different times in two growing seasons. Avena sterilis proved to be a generalist species when growing in monoculture, with similar seed production, regardless of the site conditions. However, when growing with the crop, differences in growth and seed production were observed at the different sites under some climatic conditions. The effect of the crop on A. sterilis biomass and seed production was more pronounced at the sites with finer textures and higher organic matter and nitrogen contents, suggesting that barley site‐specific competitive ability may contribute to limiting weed populations in favourable soils. 相似文献
13.
对吸水剂抗旱作用机理一些问题的探讨 总被引：6，自引：1，他引：6
本文对二种吸水剂不同相对湿度条件下的吸水能力和保水能力等特性进行了研究 ,并以小麦种子为植物材料 ,观察了不同吸水程度的吸水剂与种子对水份的竞争能力 ,结果表明 ,吸水剂对环境中水份的吸收及对种子释放水份是相互矛盾的 ,一般情况下 ,吸水剂不可能向环境中吸收水份而后供给种子萌发。吸水剂对种子萌发的促进作用是需一定条件的 相似文献
14.
在甘肃省进行了连续4 a施用农业废弃物组合肥制种玉米田理化性质及酶活性和重金属变化特征研究。 结果表明：农业废弃物组合肥施用量比例为秸秆组合肥18 t·hm-2∶畜禽粪便组合肥36 t·hm-2∶废渣组合肥15 t·hm-2。施用农业废弃物组合肥4 a与不施肥比较,制种玉米田容重、pH值和真菌数量分别降低6.77%、6.20%和26.19%;总孔隙度、水稳性团聚体、总持水量、EC值、可溶性盐和CEC分别增加6.63%、18.95%、6.62%、5.23%、5.36%和36.10%;有机质、有机碳、有机碳密度、碱解氮、速效磷和速效钾含量分别增加23.72%、24.10%、15.48%、28.44%、49.92%和27.97%;细菌数量、放线菌数量、蔗糖酶、 脲酶、磷酸酶和多酚氧化酶活性分别增加38.20%、86.60%、63.46%、38.89%、61.48%和58.82%;Hg、Cd、Cr、Pb和Zn含量分别增加21.74%、30.00%、24.49%、27.55%和31.81%。农业废弃物组合肥施用年限与制种玉米田容重、pH值和真菌数量之间呈显著负相关关系,与总孔隙度、水稳性团聚体、CEC、EC值、可溶性盐、总持水量、有机质、有机碳密度、速效氮磷钾含量、细菌数量、放线菌数量、酶活性、重金属含量之间呈显著正相关关系。 虽然连续4 a施用农业废弃物组合肥重金属含量比不施肥高,但重金属含量小于土壤污染临界值,说明研究区域农业废弃物组合肥重金属含量较低,不会对作物造成风险。 相似文献
15.
解淀粉芽胞杆菌Bacillus amyloliquefaciens PHODB35是一株具有抑菌和促生作用的多功能菌株。为了明确其对小麦的促生作用,通过离体平皿法研究菌株PHODB35发酵液对小麦种子萌发和幼苗生长的影响。结果表明,菌株PHODB35发酵液对种子萌发和芽长生长存在不同程度影响,其中高浓度发酵液（10×108和2×108 CFU/mL）对上述指标具有抑制作用,低浓度发酵液（1×108、1×107、2×106和1×106 CFU/mL）对种子萌发不存在显著影响,但促进芽长的生长,其增长幅度为13.48%~20.22%,初步明确了菌株PHODB35适宜的接种浓度为1×108 CFU/mL。温室盆栽试验表明,在该接种浓度处理后小麦的株高、鲜重、干重和基质有效磷含量均有不同程度的增加。同时以该菌株为活性成分研制的有机肥料（浓度为1×108 CFU/g）的盆栽试验结果表明,随着PHODB35有机肥用量的增加,分别提高了基质有效磷和小麦植株全磷含量3.86和3.55倍,其促生作用优于普通有机肥。多地区的田间试验表明,PHODB35有机肥处理（T3）在产量方面高于化学肥料减施处理（T2）,增产率5.31%~9.06%。该研究结果为解淀粉芽胞杆菌PHODB35有机肥的进一步产业化开发和应用提供了科学依据。 相似文献
16.
Abstract Field experiments were conducted at Jobner (Rajasthan) during the winter seasons of 1982 and 1983 to evaluate certain physical and chemical weed control systems in fenugreek at two levels of applied phosphorus. The experiments comprised four herbicides (fluchloralin, pendimethalin, thiobencarb, and chloramben) at two levels each, manual weeding at three levels; and an unweeded check. The second factor, namely, application of phosphorus was evaluated at 0 and 40 kg P2O5/ha. The soil of the experiment site was loamy sand, containing 0.16% organic carbon. The results showed that amongst the herbicides, preemergent pendimethalin at 0.75 kg/ha controlled the weeds most effectively and gave 8.91 q/ha fenugreek seed yield, which was more than twice the seed yield obtained from the unweeded check plots. The twice hoed plots were found to give 1.32 q/ha higher seed yield than the pendimethalin herbicide treatment, but the benefit‐cost ratio was found higher for the herbicidal treatment. Application of phosphorus at 40 kg P2O5/ha was found to bring about significant increase in the seed yield of fenugreek by 59 kg/ha over control, without any interaction with the weed control treatments. 相似文献
17.
Schmitt A. Koch E. Stephan D. Kromphardt C. Jahn M. Krauthausen H. -J. Forsberg G. Werner S. Amein T. Wright S. A. I. Tinivella F. van der Wolf J. P S. 《植物病害和植物保护杂志》2009,116(5):200-207
Journal of Plant Diseases and Protection - The aim of the present study was to identify seed treatment methods for eradicating Phoma valerianellae from lamb`s lettuce seeds in organic vegetable... 相似文献
18.
苦豆子种子特性与种群扩展关系的研究 总被引：8，自引：2，他引：8
苦豆子(Sophora alopecuroides L.)种子体积大,千粒重达21.6g。种皮较厚,制约了种子的萌发,采用浓硫酸浸种和机械磨损破坏种皮明显提高了萌发率。种子散布主要依靠自身重力,其散布格局是聚集型散布,多分布在母株周围,为该区域的种子库提供较多的种质资源。此外,还有动物散布和水力作用的散布,使种子能传播较远的距离,同时种子被采食后,通过消化道的磨损使种皮的通透性提高,促进了种子的萌发。 相似文献
19.
浑善达克沙地南缘沙化草地围封过程中土壤种子库与地上植被的耦合关系 总被引：16，自引：0，他引：16
在浑善达克沙地南缘,以围封不同年限的沙化草地(1年、4年、9年)为试验样地,并以未围封沙化草地作对照,深入研究了沙化草地围封过程中,土壤种子库与地上植被的耦合关系。结果表明,对沙化草地实施围栏封育,可显著提高土壤种子库与地上植被的物种丰富度;不同围封年限间,二者在植被群落组成上,均表现出较高的相似性,且相临阶段相似性较高,随围封年限差异的增加,相似性逐渐减小,但这一变化前者滞后于后者,表明草地在恢复演替中,前者较后者具有滞后性;4种类型样地之间,土壤种子库密度以及地上植被密度差异均极显著,且二者之间均存在显著正相关性,其关系均可用二次曲线描述。 相似文献
20.
生态炭肥防控小麦根腐病效果及对土壤健康修复机理分析 总被引：4，自引：0，他引：4
为探索生态炭肥(以生物质炭为主要成分)防治小麦根腐病的效果及对土壤健康的修复机理,通过设置2个生态炭肥处理分析其对小麦根腐病的发病率和病情指数、小麦产量、土壤有机质含量、土壤细菌数量及土壤酶活性的影响。结果表明,生态炭肥防控小麦根腐病效果明显,1 200kg/hm2和750 kg/hm2两个处理的防效均达到77.00%以上,最高可达86.25%;且对小麦增产增收效果显著,2个处理的小麦产量减损率分别为86.62%和76.11%,净增产值分别为7 315.52元/hm2和7 038.04元/hm2;施用生态炭肥均能有效提高小麦返青期和灌浆期的土壤有机质含量、细菌数量及土壤蔗糖酶、淀粉酶及纤维素酶活性;且施用生态炭肥对小麦根腐病的防效及对土壤健康修复作用存在正剂量效应。表明麦田增施生态炭肥是一个能快速修复土壤健康、有效防控小麦根腐病的新途径。 相似文献