杂草科学管理——理论基础与实施途径

Scientific management of weeds is theoretically based on ecology.The implementation methods incladeIntensifying the weed biology and ecology research, especially those of the heavy weeds;Intensifying the research of developing competition between the crop and the weed;Utilizing a allelopathy the gene engineering and breeding against the weeds;Utilizing allelopathy between the crop and the weed, and utilizing biological and agricultural measurements to control the weeds.     

Interactions between national and local strategies for the management of aquatic weeds

Management of aquatic weeds is often handled primarily at the local level. However, both water and water weeds do not recognise political boundaries even when these coincide with rivers or catchment areas. Thus potentially effective management of a weed in one area may be undermined by absence of a complementary program of management in an adjacent area. Authorities in each of the eight States or Territories that make up Australia are separately responsible for managing water weeds in their own State or Territory. Originally there was little coordination of these programs, but during the 1980s a national strategy for control of Australian water weeds has been progressively devised and put into practice. This stresses prevention and includes policies on plant importation, nomination of noxious weeds, development of a research strategy, a public awareness campaign, guidelines on the use of herbicides in or near water, and a field guide. This strategy is currently being incorporated into a National Weeds Strategy.     

Evolutionary-thinking in agricultural weed management

Agricultural weeds evolve in response to crop cultivation. Nevertheless, the central importance of evolutionary ecology for understanding weed invasion, persistence and management in agroecosystems is not widely acknowledged. This paper calls for more evolutionarily-enlightened weed management, in which management principles are informed by evolutionary biology to prevent or minimize weed adaptation and spread. As a first step, a greater knowledge of the extent, structure and significance of genetic variation within and between weed populations is required to fully assess the potential for weed adaptation. The evolution of resistance to herbicides is a classic example of weed adaptation. Even here, most research focuses on describing the physiological and molecular basis of resistance, rather than conducting studies to better understand the evolutionary dynamics of selection for resistance. We suggest approaches to increase the application of evolutionary-thinking to herbicide resistance research. Weed population dynamics models are increasingly important tools in weed management, yet these models often ignore intrapopulation and interpopulation variability, neglecting the potential for weed adaptation in response to management. Future agricultural weed management can benefit from greater integration of ecological and evolutionary principles to predict the long-term responses of weed populations to changing weed management, agricultural environments and global climate.     

Environmental weeds in Australia and New Zealand: issues and approaches to management

Environmental weeds are plants that invade natural ecosystems and are considered to be a serious threat to nature conservation. Australia and New Zealand, where biota with a high degree of endemism have evolved, are particularly susceptible to environmental weeds. Environmental weeds have been implicated in the extinction of several indigenous plant species, and they also threaten ecosystem stability and functional complexity. Historically, emphasis has been placed on the chemical or manual ‘control’ of weed infestations, often with little consideration of the long‐term effectiveness or the ecological consequences of such an approach. As the threat from environmental weeds is becoming more fully recognized, an integrated, strategic and ecological approach to weed management is being recommended. In both countries, systems for screening new plants before allowing entry for cultivation have been developed. For already established plants, management is conducted within a legislative and policy framework such as the Regional Pest Management Strategies that operate through the Biosecurity Act 1993 in New Zealand. Noxious weed legislation in Australia has historically focused on agricultural weeds, but some Acts are (or have recently been) undergoing revision to give greater emphasis to environmental weeds and the involvement of the community in weed management. Quarantine, legislation, research and on‐ground management are complemented by education programmes about the impact and control of environmental weeds. This paper provides an overview of the ‘tool‐kit’ needed to manage environmental weeds in Australia and New Zealand, comparing and contrasting the approaches taken in the two countries. It also provides a broad framework for the case studies that make up this special issue on the ecology and management of environmental weeds in both countries.     

Nipping aquatic plant invasions in the bud: weed risk assessment and the trade

The importation and sale of ornamental pond and aquarium plants is the most important pathway for the introduction of potential aquatic weeds into and subsequent spread of these within a country. Most current aquatic weeds were at one time deliberately imported for ornamental use. This article discusses a weed risk assessment approach to evaluating new potential weeds. It assesses the potential invasiveness of an aquatic plant based on its habitat versatility, competitive ability, reproductive output and dispersal mechanisms, range of potential impacts, potential distribution and resistance to management activities. The Aquatic Weed Risk Assessment Model (AWRAM) has been used to evaluate potential aquatic weeds in New Zealand, Australia and the USA. A similar approach could be used to guide the management of aquatic weeds in Europe. Banning the importation of highly ranked species effectively keeps biosecurity risks off-shore. Assessment of aquatic plant trade patterns, especially volumes of high-risk species, along with knowledge of current and potential distribution of those species and ease of management, are all factors to be considered when evaluating candidate plants for prevention of sale and distribution. This is a highly effective way of restricting both long-distance dispersal and density of propagules. A cooperative approach involving researchers, policy and trade representatives has been an effective way to achieve regulation of this risk pathway. European initiatives to prevent the distribution of potential aquatic weeds include the preparation of lists of known invasive aquatic species by the European and Mediterranean Plant Protection Organization (EPPO), with recommendations to member countries to consider measures to prevent their spread (e.g. banning importation of, banning sale and distribution of, and undertaking control programmes against those species). Belgian initiatives include an upcoming Royal Decree concerning the importation, exportation and possession of non-native invasive species, development of codes of conduct with the horticultural sector and prohibiting the sale, purchase and intentional release of these species in the wild. This article reviews these approaches and discusses other species of concern.     

Field assessment of a frond-feeding weevil, a successful biological control agent of red waterfern, Azolla filiculoides, in southern Africa

Azolla filiculoides (red waterfern) is a small, floating fern native to South America, that has invaded aquatic habitats, predominantly water resevoirs in southern Africa. A frond-feeding weevil, Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae), was imported from Florida, USA, and released as a biological control agent against this weed in South Africa at the end of 1997. To date, 24,700 weevils have been released, which has resulted in local extinction of red waterfern at 81% of the 112 release sites. The weevil has not failed to control a single site. Several sites were, however, lost due to flooding or drainage of dams. The surface area of weed controlled totalled 203.5 ha. On average, A. filiculoides was controlled in infested sites in 6.9 (±4.3) months. The weed recolonized at 22 of the sites (through either spore germination or dispersal by waterfowl), but the weevils subsequently spread to all of these sites and successfully caused local extinction of the weed at 18 of the sites. Five years after the release of the weevil, the weed no longer poses a threat to aquatic systems in southern Africa. In comparison to other biological control programs of aquatic weeds, the program against A. filiculoides in southern Africa ranks among the most successful cases anywhere in the world.     

Weed invasions in wetlands of Australia's Top End: reasons and solutions

Weed invasions are an increasing threat to the extensive wetlands of the Northern Territory's wet-dry tropics. Although the conservation value of these wetlands is in some ways undisputed, it is evident from the Government's multiple land use policy that it is also misunderstood. This policy aims to maximise economic returns from wetlands while protecting their ecological integrity at a time when ecological and economic costs associated with weeds are, at least in the short term, set to worsen. The underlying reasons behind wetland loss and degradation in Australia parallel those identified in Mediterranean Europe where there was antipathy from bureaucracies toward science and ecology. Several case studies from the Northern Territory explore how ecological, anthropogenic, political and economic factors contribute to weed problems. Caution is necessary when translating experience from agricultural weeds to environmental weeds. Managers have not always heeded the advice of specialists and practitioners, whose understanding of the ecological basis to weed invasions is not in as parlous a state as sometimes thought. Even when faced with sound information from which to manage, it was non-ecological reasons that slowed down or prevented effective weed control. If the floristic identity and diversity of Australia's natural wetlands is to be retained, then weeds need serious and immediate attention. Weed impacts progress beyond loss of wetland habitat and biodiversity to regional changes in landscape processes. We advocate that governments and industry recognise and address the underlying non-ecological reasons that exacerbate weed problems and set priorities to fund relevant practical studies and control programs that enable inventive weed management. Cooperation between land users, custodians and the wider community can help to overcome bureaucratic obstacles and enable judicious weed control that contributes effectively to wetland protection.     

Early establishment of planted Retama sphaerocarpa seedlings under different levels of light,water and weed competition

Large amounts of former cropland are being abandoned in developedregions. To formulate guidelines for land reclamation programmes, we exploredthe effects of artificial shading, irrigation, and removal of weed competitionon the performance of Retama sphaerocarpa (L.) Boiss.seedlings in a factorial experiment located in an abandoned cropland in CentralSpain. R. sphaerocarpa is of interest for revegetationbecause it is a drought tolerant leguminous shrub that is a major structuralcomponent of the native plant community. Seedling performance was evaluated inthree ways: seedling survivorship, growth, and photochemical efficiency. Wealsomeasured soil moisture and weed biomass production and found that bothincreasedunder artificial shading conditions. Soil moisture increased very slightlywhereweeds were removed. Thus, increased transpiration from weeds outweighed reducedevaporation from soils due to shading by weeds. Artificial shading was the mosteffective treatment for seedling survivorship, followed by removal ofcompetition by weeds. After summer, 34 % of the seedlings survived in the mostfavourable conditions (artificially shaded plots where weeds were removed),compared to ca. 1 % in full-light plots with no removal of weed competition. Apositive effect of irrigation was found for growth of seedling cover and heightin shaded plots. The analysis of photochemical efficiency pointed out therelevance of weed competition removal, and confirmed the usefulness of fastfluorescence transient techniques for the quantification of seedlingperformance. The data suggest that competition between seedlings and weeds wasprimarily for water rather than for light. We conclude that i) artificialshading improved seedling performance, but this is a little practical techniquebecause of its cost; ii) as weeds compete with, rather than facilitate, plantedseedlings, weed clipping around the seedlings is a feasible technique thatwouldimprove seedling survival; and iii) seedling performance could alsoconsiderablyimprove with a higher irrigation than was used in this experiment(75lm^–2 per growth period), provided that weedsare removed.     

Weed Management in Rice: Wheat Rotation by Allelopathy

Rice is major crop in India and its cultivation in northwest India started 25 to 30 years ago in assured irrigation areas during the summer rainy season. In this region, rice-wheat rotation became most popular owing to its high yields; however, these crops are highly infested by the weeds, thus farmers use herbicides for their control. Hence, this rotation consumes a maximum quantity of herbicides in this region, which has resulted in several problems (environmental pollution, human health hazards, development of herbicide resistance in weeds). Thus, serious ecological questions about the reliance on herbicides for weed control in this rotation have been raised. One of the alternatives to overcome these problems is with the use of allelopathic strategies, including the use of weed-smothering crops for weed management and for the sustainability of agriculture. The field, pot culture, and laboratory studies have shown that inclusion of weed-smothering crops in rotation considerably reduced the weed population in the current and succeeding crops. Early summer (April-June) fodder crops of sorghum, pearlmillet and maize drastically smothered the weed population and biomass. The residual suppression effect of peralmillet also persisted in the next crop up to 45 days. Thus, it is conceptualized that the inclusion of such summer fodder crops before the rice crop in the rice-wheat rotation may provide satisfactory weed control in the succeeding rice crop and may minimize the use of herbicides. Likewise, the replacement of wheat by winter fodder crops of oat and berseem (Trifolium alexandrinum) may also help in the control of winter weeds. Hence, further studies in this direction may provide satisfactory weed management in rice-wheat rotation and may minimize the use of herbicides and thereby help indeveloping sustainable agricultural practices.     

长期稻鸭共作对稻田杂草群落组成及物种多样性的影响

2000~2003年连续4年研究了稻鸭共作条件下田间杂草群落的特征及其动态变化规律。结果表明,在长期稻鸭共作条件下,田间杂草密度逐年降低,下降趋势符合阻滞模型y=k+a·e^bx,模型参数b反映了杂草种群的下降速率。在稻田6种主要杂草中,水虱草(Fimbristylis miliaceae)、陌上菜(Lindernia procumbens)、丁香蓼(Ludwigia prostrata)种群数量降低较快,鸭舌草(Monochoria vaginalis)、异型莎草(Cyperus difformis)次之,稗(Echinochloa crusgalli)最慢。稻鸭共作使稻田杂草群落的物种多样性持续降低,群落均匀度提高,群落相似性与稻鸭共作前相比逐年降低。说明稻鸭共作改变了田间杂草的群落结构,有利于限制杂草的发生危害。随着稻鸭共作的连年进行,对田间杂草的控制效果逐渐上升,4年后达99%以上。稻鸭共作是稻田替代化学除草的一种非常有效的生物、生态控草措施,具有显著的经济和生态效益。     

A review of the integration of classical biological control with other techniques to manage invasive weeds in natural areas and rangelands

Integrating classical biological control with other management techniques such as herbicide, fire, mechanical control, grazing, or plant competition, can be the most effective way to manage invasive weeds in natural areas and rangelands. Biological control agents can be protected from potential negative impacts of these weed control methods through untreated refugia or by applying the treatment at a time when the agent is not vulnerable. A literature review of experiments that integrated biological control with other management strategies from 1987 to 2017 yielded 39 terrestrial and 16 aquatic studies. The tactics most frequently integrated with biological control were herbicide applications and plant competition. Despite numerous examples of successful programs and calls for more widespread integration of biological control with other weed management strategies, there was no increase in the number of studies reported annually over time. Additional studies investigating the ecological and economic benefits of integrated weed management are needed.     

杂草生防作用物对本土生物群落的影响

传统生物防治是治理外来入侵杂草危害切实可行的有效策略和途径,近来对传统生物防治的批评主要集注于,引进的生防作用物攻击威胁本土非靶标生物。引进的生防作用物可能对本土非靶标生物产生直接和间接影响,这类影响通过不同营养级生物之间的取食关系,以及通过同一营养级内生物间的竞争关系,而影响本土非靶标生物群落。列举若干杂草生物防治案例对以上影响方式及其发生途径进行了评述。就防范杂草生防作用物对非靶标生物的负面影响,提出了以下对策:(i)把引进天敌防治外来入侵生物作为最后的有效手段;(ii)适当增加对非靶标生物潜在影响的生态学评估;(iii)选择寄主专一性强而且能有效控制靶标杂草的天敌;(iv)加强对杂草传统生物防治的生态学研究。     

Co-composting invasive aquatic macrophytes and pond sediment holds the potential for environmental amelioration: Selecting the right shade of grey

Co-composting of invasive aquatic weeds with pond sediment can be a cost-effective way to manage the problem of invasion and eutrophication in aquatic systems and improvement of soil fertility in agricultural systems. Nevertheless, preparation of good quality compost is a challenge because of the variations in the physico-chemical properties of the plant material and the bulking agent. Mixing the plant biomass and the bulking agent in an appropriate proportion is crucial to make good quality compost, which requires a systematic empirical study. We standardized a protocol for composting Eichhornia crassipes and Ipomoea carnea biomass using pond sediment as a bulking agent. For each species, we used a randomized block design with 3 treatments × 3 replicates. The study revealed that mixing pond sediment and the weed biomass in 1:5 ratio yielded better quality compost in both the species compared to other treatments. The study emphasizes that composting aquatic weeds with pond sediment should help in managing the problem of weed invasion, sedimentation, eutrophication, and loss of soil fertility in agricultural fields.     

稻田水面漂浮的杂草种子种类及动态

为了揭示杂草种子的漂浮动态,并为探寻生态控草方法提供理论依据,我们于2005年6-11月,在南京沧波门稻作区调查了水稻种植前及生长后期田问杂草群落以及稻田灌水期间水面漂浮的杂草种子的种类及漂浮时间.结果表明,在水稻种植前及生长后期田间出现有15科24种杂草;可漂浮于水面的杂草种子有17科26种,与田间发生的杂草种类相同的共有18种,占所有32种杂草的56.25%.这些杂草主要隶属于禾本科、蓼科、毛茛科、报春花科、莎草科、菊科和雨久花科.田埂附近漂浮的杂草种类及种子数量均高于田中间;各类杂草种子的漂浮能力不一,其中菵草(Beckmannia syzigachne)、泽珍珠菜(Lysimachia candida)、茴茴蒜(Ranunculus chinensis)、齿果酸模(Rumex dentatus)、蛇床(Cnidium monnieri)、鳢肠(Eclipta prostrata)和看麦娘(Alopecurus aequalis)等在田间水面漂浮能力较强.漂浮期间杂草种子除多集中于田埂附近,也附着于稻稞周围,并有互相结联的趋势.从整体上看,杂草种子漂浮2天后骤降,8天后基本全部沉降.显然,稻田生境的杂草种子大多可以漂浮于水面传播扩散.因此在灌水早期采取过滤或清除水上漂浮杂草种子可以减少杂草种子的输入和加速杂草种子从田间输出,减少杂草发生基数.     

Searching for weeds – how to search where the weeds are?

Sampling for rare events, such as a new weed incursion, is not easy. At most of the sample points the species of interest is absent and only occasionally the species is recorded. Very often surveillance and monitoring for rare events (e.g. new weed incursions) is done using local knowledge and a statistical sampling design is not used. The stated reason for this approach is usually because the biodiversity managers knew where to look and didn’t need statistics. Adaptive, unequal probability survey designs can be used in these situations, ensuring both sample effort is focused on locations where there is a high likelihood of a weed being present. Time in the field is spent within locations where weeds are present and minimal time spent where weeds are absent. Any relevant information on where weeds are likely to be found (e.g. local knowledge and expertise) can be used to target survey effort in unequal probability survey designs. The advantage of an adaptive, unequal probability survey design is that not only can field effort be focused on areas where the weeds are thought to be. In addition, important weed parameters can be estimated and reported along with estimates of uncertainty. Weed parameters include the proportion of the total area that weeds are present, the diversity of weed species, the total abundance of weeds, and the total area covered by weeds. With reliable and consistent estimates of these weed parameters (e.g. weed cover or abundance) the efficacy of weed management can be tracked. Over time, with regular reporting of weed cover or abundance, the success (or otherwise) of weed management strategies can be measured.     

Does weed suppression by high crop density depend on crop spatial pattern and soil water availability?

Size-asymmetric competition, in which larger plants obtain a disproportionally larger share of contested resources, can be applied in agriculture to suppress weeds by increasing crop density and spatial uniformity, as these practices enhance the initial size-asymmetric competitive advantages of crop seedlings over weed seedlings early in the growing season. We do not yet know how agronomic factors influence weed suppression at high crop density. We performed a field experiment to ask how crop density, spatial pattern and irrigation interact to influence weed suppression and grain yield in semi-arid croplands. The experimental was a factorial design with 4 factors: wheat cultivar (Ningchun4, Xihan2), irrigation level (control, irrigated), sowing density (low, 196 seeds m⁻²; moderate, 400 seeds m^-2; high, 625 seeds m⁻²), and spatial sowing pattern (rows, uniform). Weed growth was effectively suppressed by increased crop density and spatial uniformity. Effects of crop density on weed suppression and grain yield were more pronounced in the uniform pattern than in crop rows. Weed biomass was 55.7% lower and grain yield increased 29.7% higher in the high density uniform pattern compared to the low density and row pattern. Crop density interacted with cultivar in determining both weed biomass and grain yield, potentially reflecting different traits regulating crop competitive ability. Irrigation and crop density had additive effects on weed biomass but interacted to influence grain yield. Our findings support the idea that increased crop density and spatial uniformity can make a valuable and environmentally friendly contribution to weed control in wheat, reducing the need for chemical or mechanical weed control. We need a better understanding of the interactions among climate, agricultural management and crop genotype to improve our ability to effectively suppress weeds with high crop density and spatial uniformity.     

Hybridization in agricultural weeds: A review from ecological,evolutionary, and management perspectives

Agricultural weeds frequently hybridize with each other or with related crop species. Some hybrid weeds exhibit heterosis (hybrid vigor), which may be stabilized through mechanisms like genome duplication or vegetative reproduction. Even when heterosis is not stabilized, hybridization events diversify weed gene pools and often enable adaptive introgression. Consequently, hybridization may promote weed evolution and exacerbate weed–crop competition. However, hybridization does not always increase weediness. Even when viable and fertile, hybrid weeds sometimes prove unsuccessful in crop fields. This review provides an overview of weed hybridization and its management implications. We describe intrinsic and extrinsic factors that influence hybrid fitness in agroecosystems. We also survey the rapidly growing literature on crop–weed hybridization and the link between hybridization and invasiveness. These topics are increasingly relevant in this era of genetic tools for crop improvement, intensive and simplified cropping systems, and globalized trade. The review concludes with suggested research priorities, including hybridization in the context of climate change, plant–insect interactions, and redesigned weed management programs. From a weed management perspective, hybridization is one of many reasons that researchers and land managers must diversify their weed control toolkits.     

长期不同施肥方式对麦田杂草群落的影响

以太湖地区农业科学研究所31a的长期肥料定位试验田为材料,分别于2011—2012年小麦苗期、拔节期和收获期进行了杂草群落调查,研究杂草类型与密度的分布、杂草多样性指数的变化,并对杂草种群分布与土壤养分因子进行冗余分析。结果表明:小飞蓬、看麦娘、大巢菜、稻槎菜、通泉草是本地区小麦生长期的主要杂草类型;随着小麦的生长以及氮肥、有机肥的施入,杂草密度呈下降趋势;施入有机肥降低了麦季杂草的群落多样性指数,在小麦生长的不同时期均衡施肥的CNPK处理以及不施肥的C0处理的群落各项多样性指数能维持在一个较高的水平。RDA分析显示土壤氮含量以及有机质含量与第一排序轴相关性大,是对杂草分布影响最大的两个土壤养分因子。太湖地区稻麦两熟制条件下,长期有机无机肥料单一或配合投入可显著影响麦田杂草的群落组成,其中氮肥和有机肥的施入能显著降低杂草密度;土壤养分的差异影响田面杂草密度和优势种群,均衡施肥能降低优势杂草种群的优势地位,抑制其发生危害程度,提高农田生态系统的生产力及稳定性。     

Allelopathic Interactions and Allelochemicals: New Possibilities for Sustainable Weed Management

Weeds are known to cause enormous losses due to their interference in agroecosystems. Because of environmental and human health concerns, worldwide efforts are being made to reduce the heavy reliance on synthetic herbicides that are used to control weeds. In this regard the phenomenon of allelopathy, which is expressed through the release of chemicals by a plant, has been suggested to be one of the possible alternatives for achieving sustainable weed management. The use of allelopathy for controlling weeds could be either through directly utilizing natural allelopathic interactions, particularly of crop plants, or by using allelochemicals as natural herbicides. In the former case, a number of crop plants with allelopathic potential can be used as cover, smother, and green manure crops for managing weeds by making desired manipulations in the cultural practices and cropping patterns. These can be suitably rotated or intercropped with main crops to manage the target weeds (including parasitic ones) selectively. Even the crop mulch/residues can also give desirable benefits. Not only the terrestrial weeds, even allelopathy can be suitably manipulated for the management of aquatic weeds. The allelochemicals present in the higher plants as well as in the microbes can be directly used for weed management on the pattern of herbicides. Their bioefficacy can be enhanced by structural changes or the synthesis of chemical analogues based on them. Further, in order to enhance the potential of allelopathic crops, several improvements can be made with the use of biotechnology or genomics and proteomics. In this context either the production of allelochemicals can be enhanced or the transgenics with foreign genes encoding for a particular weed-suppressing allelochemical could be produced. In the former, both conventional breeding and molecular genetical techniques are useful. However, with conventional breeding being slow and difficult, more emphasis is laid on the use of modern techniques such as molecular markers and the selection aided by them. Although the progress in this regard is slow, nevertheless some promising results are coming and more are expected in future. This review attempts to discuss all these aspects of allelopathy for the sustainable management of weeds. Referee: Dr. Amrjits S. Basra, Central Plains Crop Technology, 5912 North Meridian Avenue, Wichita, KS 67204     

模拟化感作物种植密度对杂草种群数量的作用

具化感作用的作物其种植密度会影响杂草的种群动态。本研究应用数学模型作为分析问题的工具,对作物化感作用下杂草种群动态进行了模型分析和计算机模拟,结果表明,当作物的种植密度较大时,杂草的种群动态数量可以得到有效的控制;而当作物种植密度低于一定数量时,其化感作用对杂草的种群动态数量影响不大。