Efficacy of cultural control methods for combating herbicide-resistant Lolium rigidum

Herbicide-resistant populations of annual ryegrass (Lolium rigidum) are estimated to affect crop production on about 5000 farms in southern Australia. In order to manage resistant populations, some farmers have adopted a two-to-three-year pasture phase which allows use of grazing by sheep, and non-selective herbicides to deplete the weed seed-bank. However, in low-to-medium rainfall zones, where financial returns from pastures are relatively low, farmers have generally combined cultural practices for weed management with the use of alternative herbicides, mainly trifluralin. Used singly, none of the currently available cultural techniques provides an adequate level of weed control. However, when used in carefully planned combinations, extremely effective ryegrass control can be achieved. Some of the important cultural practices for ryegrass control include delayed sowing (sometimes in conjunction with a shallow autumn cultivation); stubble burning; cutting the crop for hay or green manure, increased crop density and capture of weed seeds at harvest. Selection of crop species and cultivars with superior weed suppression potential is also receiving considerable attention. ©1997 SCI     

Our top 10 herbicide‐resistant weed management practices

Although proactive or reactive herbicide‐resistant weed management (HRWM) practices have been recommended to growers in different agroecoregions globally, there is a need to identify and prioritise those having the most impact in mitigating or managing herbicide selection pressure in the northern Great Plains of North America. Our perspective on this issue is based on collaborative research, extension activities and dialogue with growers or farming experience (cereal, oilseed and pulse crop production) during the past 30 years. We list our top 10 HRWM practices, concluding with the number 1 practice which is the foundation of the other nine practices: crop diversity. Although our top 10 HRWM practices have broad applicability across agroecoregions, their ranking may vary widely. © 2017 Society of Chemical Industry     

Herbicide‐resistant weed management: focus on glyphosate

This review focuses on proactive and reactive management of glyphosate‐resistant (GR) weeds. Glyphosate resistance in weeds has evolved under recurrent glyphosate usage, with little or no diversity in weed management practices. The main herbicide strategy for proactively or reactively managing GR weeds is to supplement glyphosate with herbicides of alternative modes of action and with soil‐residual activity. These herbicides can be applied in sequences or mixtures. Proactive or reactive GR weed management can be aided by crop cultivars with alternative single or stacked herbicide‐resistance traits, which will become increasingly available to growers in the future. Many growers with GR weeds continue to use glyphosate because of its economical broad‐spectrum weed control. Government farm policies, pesticide regulatory policies and industry actions should encourage growers to adopt a more proactive approach to GR weed management by providing the best information and training on management practices, information on the benefits of proactive management and voluntary incentives, as appropriate. Results from recent surveys in the United States indicate that such a change in grower attitudes may be occurring because of enhanced awareness of the benefits of proactive management and the relative cost of the reactive management of GR weeds. Copyright © 2011 Society of Chemical Industry     

Integrated pest management and weed management in the United States and Canada

There is interest in more diverse weed management tactics because of evolved herbicide resistance in important weeds in many US and Canadian crop systems. While herbicide resistance in weeds is not new, the issue has become critical because of the adoption of simple, convenient and inexpensive crop systems based on genetically engineered glyphosate‐tolerant crop cultivars. Importantly, genetic engineering has not been a factor in rice and wheat, two globally important food crops. There are many tactics that help to mitigate herbicide resistance in weeds and should be widely adopted. Evolved herbicide resistance in key weeds has influenced a limited number of growers to include a more diverse suite of tactics to supplement existing herbicidal tactics. Most growers still emphasize herbicides, often to the exclusion of alternative tactics. Application of integrated pest management for weeds is better characterized as integrated weed management, and more typically integrated herbicide management. However, adoption of diverse weed management tactics is limited. Modifying herbicide use will not solve herbicide resistance in weeds, and the relief provided by different herbicide use practices is generally short‐lived at best. More diversity of tactics for weed management must be incorporated in crop systems. © 2014 Society of Chemical Industry     

Biological control of weeds in European crops: recent achievements and future work

Approaches to the biological control of weeds in arable crops and integration of biological weed control with other methods of weed management are broadly discussed. Various types of integrative approaches to biological control of weeds in crops have been studied within the framework of a concerted European Research Programme (COST‐816). During the period 1994–99, some 25 institutions from 16 countries have concentrated on five target weed complexes. Some major scientific achievements of COST‐816 are: (i) combination of the pathogen Ascochyta caulina with an isolated phytotoxin produced by this fungus to control Chenopodium album in maize and sugar beet; (ii) the elaboration and preliminary field application of a system management approach using the weed:pathogen system Senecio vulgaris:Puccinia lagenophorae to reduce the competitiveness of the weed by inducing and stimulating a disease epidemic; (iii) combination of underseeded green cover with the application of spores of Stagonospora convolvuli to control Convolvulus species in maize; (iv) assessment of the response of different provenances of Amaranthus spp. to infection by Alternaria alternata and Trematophoma lignicola, the development of formulation and delivery techniques and a field survey of native insect species to control Amaranthus spp. in sugar beet and maize; (v) isolation of strains of different Fusarium spp. that infect all the economically important Orobanche spp. and development of novel, storable formulations using mycelia from liquid culture. Although no practical control has yet been reached for any of the five target weeds, potential solutions have been clearly identified. Two major routes may be followed in future work. The first is a technological approach focusing on a single, highly destructive disease cycle of the control agent and optimizing the efficacy and specificity of the agent. The second is an ecological approach based on a better understanding of the interactions among the crop, the weed, the natural antagonist and the environment, which must be managed in order to maximize the spread and impact of an indigenous antagonist on the weed.     

Perspectives on transgenic,herbicide‐resistant crops in the United States almost 20 years after introduction

Herbicide‐resistant crops have had a profound impact on weed management. Most of the impact has been by glyphosate‐resistant maize, cotton, soybean and canola. Significant economic savings, yield increases and more efficacious and simplified weed management have resulted in widespread adoption of the technology. Initially, glyphosate‐resistant crops enabled significantly reduced tillage and reduced the environmental impact of weed management. Continuous use of glyphosate with glyphosate‐resistant crops over broad areas facilitated the evolution of glyphosate‐resistant weeds, which have resulted in increases in the use of tillage and other herbicides with glyphosate, reducing some of the initial environmental benefits of glyphosate‐resistant crops. Transgenic crops with resistance to auxinic herbicides, as well as to herbicides that inhibit acetolactate synthase, acetyl‐CoA carboxylase and hydroxyphenylpyruvate dioxygenase, stacked with glyphosate and/or glufosinate resistance, will become available in the next few years. These technologies will provide additional weed management options for farmers, but will not have all of the positive effects (reduced cost, simplified weed management, lowered environmental impact and reduced tillage) that glyphosate‐resistant crops had initially. In the more distant future, other herbicide‐resistant crops (including non‐transgenic ones), herbicides with new modes of action and technologies that are currently in their infancy (e.g. bioherbicides, sprayable herbicidal RNAi and/or robotic weeding) may affect the role of transgenic, herbicide‐resistant crops in weed management. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

我国耐除草剂转基因作物研发与产业化应用前景

基因重组技术的发展突破了作物有性杂交的限制, 为培育耐除草剂作物提供了新途径。转基因作物种植产生了显著的经济效益、社会效益和生态效益, 种植面积迅速增长。全球转基因作物1996年仅170万hm2, 2022年种植面积扩大到2.022亿hm2, 增加了近120倍。面积最大的前5个国家转基因作物种植比例均在90%以上, 阿根廷种植比例接近100%, 耐除草剂性状一直是转基因作物的主要性状。2008年, 我国启动了转基因生物新品种培育科技重大专项, 利用生物育种技术研发出中黄6106、DBN8002、DBN9936、DBN9858、DBN3601T等多个含有耐除草剂草甘膦基因的转化体, 并获得农业转基因生物生产应用安全证书。2021年-2023年, 我国在云南、内蒙古等地开展了转基因作物试点种植, 结果表明, 草甘膦在上述转化体及其衍生品种上应用, 除草效果好、增产节本优势明显, 适合不同的轮作与栽培模式。本文概述全球转基因作物的研发和商业化应用情况, 分析我国农田杂草危害现状及防控需求, 结合具体国情和转基因耐除草剂作物应用需求, 论述其在我国产业化应用的前景, 以期为转基因耐除草剂作物的研究、种植和草害可持续控制提供参考。     

A survey of Lolium rigidum populations in citrus orchards: Factors explaining infestation levels

The presence of herbicide‐resistant Lolium rigidum in Mediterranean (Spanish) citrus orchards was reported in 2005 and it poses a serious threat to crop management. The main objective of this research was to investigate which components could be responsible for the persistence of annual ryegrass populations in Mediterranean mandarin and orange orchards. This is the first study regarding L. rigidum populations in Mediterranean citrus orchards. Surveys were conducted in 55 commercial citrus orchards in eastern Spain in 2013 by interviewing technicians who were working in cooperatives about crop management. The level of infestation by L. rigidum and the presence of harvester ants (Messor barbarus) then were estimated in the same orchards. The variables were subjected to a two‐dimensional analysis and both univariate and multivariate logistic regression models were fitted for each of the three L. rigidum density levels that had been established. The multivariate models showed the significant factors that were associated with various L. rigidum densities: (i) at a low density, the herbicides that were applied, the number of applications in 2013 and the type of irrigation (flood or drip); (ii) at a medium density, the presence of harvester ants; and (iii) at a high density, the herbicides that were applied in 2013. The results indicated that drip irrigation and one application of glyphosate mixed with other herbicides (or herbicides other than glyphosate) were associated with a lower L. rigidum density. The alternative management options that are presented here should help farmers to reduce weed problems in Mediterranean citrus orchards. Future research is required to better understand the presence of herbicide‐resistant populations, as well as the possible beneficial presence of granivorous ant species.     

Reduced herbicide doses in field crops: A review

Farmers are becoming increasingly interested in more comprehensive weed management programs that reduce weed populations over time and in the use of reduced herbicide doses that lower their production costs. Research indicates that there is good potential to reduce the number of herbicide applications and utilize lower herbicide doses within competitive cropping systems. Diverse crop rotations, competitive cultivars, higher crop seed rates, reduced row spacing, specific fertilizer placement, and cover crops have been identified as integral components of competitive cropping systems. This review paper explores the potential for successful use of reduced herbicide doses within competitive cropping systems that have a multiyear approach to weed management. The utilization of decision support systems or new methods of assessing active weed growth are discussed in light of further enhancing the successful use of reduced herbicide doses and advising farmers on when (and when not) they might be a viable option.     

Integrated weed management: Quo vadis?

The different components of Integrated Weed Management (IWM), such as crop selection, crop husbandry, plant nutrition, crop protection, farm hygiene, and the site-specific conditions, all are factors having an influence on the successful adoption of the basic IWM concept. Farmers' field activities, directly or indirectly, affect germination and development of weeds as well as weed population dynamics. However, also important non-agronomic parameters indirectly affect weed management. They include farm structure, farmers' personal targets and preferences, the provision and communication of technical know-how, economics, but also demands from society and in the area of ecology. In the light of the many additional important influences and interactions, rather than thinking in terms of IWM, it seems appropriate to view crop production as a whole process, probably best defined as Integrated Crop Management (ICM). Boiling down the mass of information and outlining a rational, straightforward, easy-to-apply and cheap approach for the site-specific weed management is needed for the successful implementation of IWM principles within the framework of ICM.     

The occurrence of herbicide-resistant weeds worldwide

The 1995/6 International Survey of Herbicide-Resistant Weeds recorded 183 herbicide-resistant weed biotypes (124 different species) in 42 countries. The increase in the number of new herbicide-resistant weeds has remained relatively constant since 1978, at an average of nine new cases per year worldwide. Whilst 61 weed species have evolved resistance to triazine herbicides, this figure now only accounts for one-third of all documented herbicide-resistant biotypes. Triazine-resistant weeds have been controlled successfully in many countries by the use of alternative herbicides. Due to the economic importance of ALS and ACCase inhibitor herbicides worldwide, and the ease with which weeds have evolved resistance to them, it is likely that ALS and ACCase inhibitor-resistant weeds will present farmers with greater problems in the next five years than triazine-resistant weeds have caused in the past 25 years. Thirty-three weed species have evolved resistance to ALS-inhibitor herbicides in 11 countries. ALS-inhibitor-resistant weeds are most problematic in cereal, corn/soybean and rice production. Thirteen weed species have evolved resistance to ACCase inhibitors, also in 11 countries. ACCase inhibitor resistance in Lolium and Avena spp. threatens cereal production in Australia, Canada, Chile, France, South Africa, Spain, the United Kingdom and the USA. Fourteen weed species have evolved resistance to urea herbicides. Isoproturon-resistant Phalaris minor infesting wheat fields in North West India and chlorotoluron-resistant Alopecurus myosuroides in Europe are of significant economic importance. Although 27 weed species have evolved resistance to bipyridilium herbicides, and 14 weed species have evolved resistance to synthetic auxins, the area infested and the availability of alternative herbicides have kept their impact minimal. The lack of alternative herbicides to control weeds with multiple herbicide resistance, such as Lolium rigidum and Alopecurus myosuroides, makes these the most challenging resistance problems. The recent discovery of glyphosate-resistant Lolium rigidum in Australia is a timely reminder that sound herbicide-resistant management strategies will remain important after the widespread adoption of glyphosate-resistant crops. ©1997 SCI     

Weed suppression by cover crops: comparative on‐farm experiments under integrated and organic conservation tillage

Cover crops are increasingly being used for weed suppression and to enhance the sustainability of agro‐ecosystems. However, the suitability of cover crops for weed suppression in integrated and organic conservation tillage systems is still poorly investigated. Therefore, a 2‐year field study at eight sites was conducted to test the weed suppressive potential of six legume‐based cover crops, with the aim to reduce herbicide input or mechanical weed management interventions. In all experiments, cover crops were directly sown after cereals before next year's main crop (grain maize or sunflower). The presence of cover crops caused a 96% to 100% reduction of weed dry matter at the four sites managed under integrated production, while effects were lower at the four sited managed under organic production, ranging from 19% to 87%. Cover crops that covered soil quickly and which produced much dry matter had the best weed suppressive potential. However, their weed suppressing effect was difficult to predict, as it depended on the year of the investigation, experimental site, cover crop species, the speed of soil cover in autumn and the density of the resulting mulch layer in spring. The study demonstrated that cover crops are a useful tool to suppress weeds under integrated and organic conservation tillage practices. Our recommendation for supporting weed management in conservation tillage systems is to use locally adapted cover crops that have rapid establishment, good soil coverage and high dry matter production. However, additional weed management measures are required for reliable weed control under on‐farm conditions.     

Preliminary findings of potentially resistant goosegrass (Eleusine indica) to glufosinate‐ammonium in Malaysia

Goosegrass (Eleusine indica), regarded as one of the world's worst weeds, is highly pernicious to cash crop‐growers in Malaysia. Following reports in 2009 that glufosinate‐ammonium failed to adequately control goosegrass populations in Kesang, Malacca, and Jerantut, Pahang, Malaysia, on‐site field trials were conducted to assess the efficacy of glufosinate‐ammonium towards goosegrass in both places. Preliminary screenings with glufosinate‐ammonium at the recommended rate of 495 g ai ha^?1 provided 82% control of the weed at a vegetable farm in Kesang, while the same rate failed to control goosegrass at an oil palm nursery in Jerantut. The ensuing greenhouse evaluations indicated that the “Kesang” biotype exhibited twofold resistance, while the “Jerantut” biotype exhibited eightfold resistance towards glufosinate‐ammonium, compared to susceptible goosegrass populations. The occurrence of glufosinate resistance in goosegrass calls for more integrated management of the weed to prevent escalating resistance and further proliferation of the weed in Malaysia.     

Tillage and herbicide treatments with inter‐row cultivation influence weed densities and yield of three industrial crops

Field experiments were conducted in northern Greece in 2003 and 2004 to evaluate effects of tillage regimes (moldboard plowing, chisel plowing, and rotary tilling), cropping sequences (continuous cotton, cotton‐sugar beet rotation, and continuous tobacco) and herbicide treatments with inter‐row hand hoeing on weed population densities. Total weed densities were not affected by tillage treatment except that of barnyardgrass (Echinochloa crus‐galli), which increased only in moldboard plowing treated plots during 2003. Redroot pigweed (Amaranthus retroflexus) and black nightshade (Solanum nigrum) densities were reduced in continuous cotton, while purple nutsedge (Cyperus rotundus), E. crus‐galli, S. nigrum, and johnsongrass (Sorghum halepense) densities were reduced in tobacco. A. retroflexus and S. nigrum were effectively controlled by all herbicide treatments with inter‐row hand hoeing, whereas E. crus‐galli was effectively reduced by herbicides applied to cotton and tobacco. S. halepense density reduction was a result of herbicide applied to tobacco with inter‐row hand hoeing. Yield of all crops was higher under moldboard plowing and herbicide treatments. Pre‐sowing and pre‐emergence herbicide treatments in cotton and pre‐transplant in tobacco integrated with inter‐row cultivation resulted in efficient control of annual weed species and good crop yields. These observations are of practical relevance to crop selection by farmers in order to maintain weed populations at economically acceptable densities through the integration of various planting dates, sustainable herbicide use and inter‐row cultivation; tools of great importance in integrated weed management systems.     

Quality versus quantity: spring wheat seed size and seeding rate effects on Avena fatua interference, economic returns and economic thresholds

A 3-year field experiment was conducted at Kalispell, Montana, USA, to investigate the effects of spring wheat seed size and seeding rate on wheat yield loss (YL), economic returns and economic thresholds (ETs), as a function of Avena fatua density. Crop competitive ability increased as wheat seeding rate and seed size increased, with the greatest differences among treatment factors being observed at low weed densities. Both treatment factors decreased spring wheat YL, increasing economic returns during all 3 years of the study despite the higher associated seed costs. Averaged over all other factors, adjusted gross returns (AGR) were 477 and 537$ ha⁻¹ for the low and high seeding rates, while values of 453, 521 and 547$ ha⁻¹ were obtained for the small, bulk and large seed size classes respectively. Weed-free yield potential varied yearly. As yield potential increased, A. fatua competitive effects were more evident and ETs decreased. Nonetheless, both treatment factors increased ETs in 2 of 3 years. These results demonstrate that the use of higher seeding rates and larger seed size classes both improve wheat competitive ability towards A. fatua while simultaneously increasing economic returns.     

抗药性杂草与治理

抗药性杂草对农田杂草治理和农业生产构成严重威胁,成为备受全球关注的严重问题。随着长期、大量使用相对有限的化学除草剂,全球抗药性杂草发展迅猛,目前已有217种杂草对化学除草剂产生了抗药性,我国抗药性杂草发展也十分迅猛。本文在介绍杂草抗药性基本概念、抗药性杂草发展过程、抗药性杂草现状的基础上,重点描述了抗药性杂草治理策略,以期为我国抗药性杂草研究和治理提供参考。     

非转基因抗除草剂作物研究现状与展望

抗除草剂转基因作物的培育和推广明显提高了农田除草效率,取得了巨大的经济效益。但随着研究的深入,外源基因的不可预测性却越来越多地阻碍了转基因作物的发展。针对转基因作物与非转基因作物的优缺点,该文系统地综述了国内外抗除草剂作物的研究现状,重点阐述了非转基因抗除草剂作物的主要研究方法及存在的问题,并提出研究对策和发展方向。     

Integrated management of Bromus diandrus in dryland cereal fields under no‐till

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.