Towards selective breeding of Atlantic salmon for sea louse resistance: approaches to identify trait markers

Several species of sea lice, in particular Lepeophtheirus salmonis (Kr?yer), affect the welfare and condition of farmed salmon, with an estimated annual cost to the Scottish industry of 15-30 Pounds million. In Atlantic salmon, some stocks show resistance to L salmonis. Such natural resistance could be utilized for stock improvement using molecular genetic technologies. The development of molecular markers linked to resistance genes, allowing the identification of resistant fish, could increase the efficacy of selective breeding programmes. Various approaches to achieve this goal are described. One way to identify genes conferring resistance is to develop screens for salmon genes that are activated upon louse infection. One such screen--differential display--requires no previous knowledge of gene sequences, involves no preconceptions about which gene families are involved and can therefore identify novel genes. Preliminary results of comparative gene expression in sea-louse-challenged and control fish illustrate the application of differential display.     

拓宽生物防治 持续治理虫害

本文针对我国生物防治资源极其丰富和农民经济实力薄弱的特点，结合我国生物防治成果，论述了应如何发展和拓宽具有我国特色的害虫生物防治，进一步提高综合防治水平，促进农业可持续发展。     

Nonchemical management of soilborne pests in fresh market vegetable production systems

ABSTRACT Nonchemical methods including host resistance, organic amendments, crop rotation, soil solarization, and cultural practices have been used to control soilborne pests in fresh market vegetable production systems. Their suitability as alternatives to methyl bromide will depend on the approach to pest management used by the grower. Traditionally, methyl bromide is used in production systems that rely on the single application of a broad-spectrum biocide to disinfest soils prior to planting. Non-chemical methods are not suitable for a single tactic approach to pest management because they do not provide the same broad spectrum of activity or consistency as fumigation with methyl bromide. Nonchemical methods are compatible with an integrated pest management (IPM) approach, where multiple tactics are used to maintain damage from pests below an economic threshold while minimizing the impact to beneficial organisms. However, adoption of IPM is hindered by the paucity of economically feasible sampling programs and thresholds for soilborne pests and by a reluctance of growers to commit additional resources to the collection and management of biological information. A novel approach to the management of soilborne pests is to design the crop production system to avoid pest outbreaks. Using this "proactive" approach, a tomato production system was developed using strip-tillage into existing bahia-grass pasture. By minimizing inputs and disruption to the pasture, growers were able to reap the rotational benefits of bahiagrass without cultivating the rotational crop. While minimizing the need for interventive procedures, a proactive approach is difficult to integrate into existing crop production systems and will require several years of testing and validation.     

Western flower thrips resistance to insecticides: detection, mechanisms and management strategies

Insecticide resistance continues to be one of the most important issues facing agricultural production. The challenges in insecticide resistance and its management are exemplified by the situation with the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). This highly invasive pest has a great propensity for developing insecticide resistance because of its biological attributes, and cases of resistance to most classes of insecticides used for its management have been detected. To combat insecticide resistance in the western flower thrips, several insecticide resistance management (IRM) programs have been developed around the world, and these are discussed. Successful programs rely on non-insecticidal tactics, such as biological and cultural controls and host plant resistance, to reduce population pressures, rotations among insecticides of different mode of action classes to conserve insecticide efficacy, resistance monitoring, sampling to determine the need for insecticide applications and education to assure proper implementation. More judicious insecticide use is possible with the development of well-founded economic thresholds for more cropping systems. While growers will continue to rely on insecticides as part of western-flower-thrips- and thrips-transmitted virus management, more effective management of these pests will be achieved by considering their management in the context of overall integrated pest management, with IRM being a key component of those comprehensive programs.     

Wild salmonids and sea louse infestations on the west coast of Scotland: sources of infection and implications for the management of marine salmon farms

The sea louse (Lepeophtheirus salmonis Kr?yer) is a major health problem for both farmed and wild salmonids. This paper investigates louse epidemiology and management in the salmon-farming zone of western Scotland. Based on a review of the marine ecology of wild salmon (Salmo salar L) and sea trout (Salmo trutta L), and catch and farm production statistics, best estimates were made for numbers of wild and farm hosts present in coastal waters in March-June 2000. Applying data for ovigerous female louse infections and fecundity, the sources and risks of larval transmission to wild salmon and sea trout were modelled. Farm salmon in the second spring of production were the primary host group (98% of fish), while numbers of wild salmonids (< 1%) and escaped farm salmon (2%) were relatively insignificant. Farm salmon produced 97% of louse eggs at high levels (eight ovigerous lice per fish), and 78% at low levels (one per fish). Wild salmonids produced < 1% of eggs under both scenarios, but escaped farm salmon produced 3% and 21%, respectively. All hosts potentially cross-infect one another, but farm salmon are more likely to infect wild and farm smolts, and also other farm salmon. Monitoring of lice on sea trout in June 1998-2000 by the Association of West Coast Fisheries Trusts corroborated the model's conclusions. Localised epizootics occurred every year and coincided with the presence of ovigerous lice on local farms. In areas of mixed-year class production on farms, epizootics were evident every spring, but occurred every second spring in areas of single-year class production. In 1998-2000 at least 14-40% of sea trout were infected with potentially lethal infestations of lice. Ovigerous louse levels of < 0.005 per fish were required on farm salmon in the spring of 2000 to produce less eggs than those emitted by wild salmonids. With the industry's continued expansion, and thus increased numbers of farm salmon, a target of zero ovigerous lice will be required on farms to minimise impacts on wild salmonids. Due to the limited long-term efficacy and availability of louse medicines, management strategies are discussed which will improve control, including single-year class production over large areas, alternate S1-S1/2 smolt inputs, and 11-month production cycles.     

Occurrence of the microsporidian parasite Nucleospora salmonis in four species of salmonids from the Massif Central of France

Nucleospora salmonis (Hedrick, Groff et Baxa, 1991), an intranuclear microsporidian parasite of marine and freshwater fish, causes diseases mainly in salmonid species. Losses have been reported in stocks of salmonid fish reared in the region of Auvergne (France). The cause of chronic mortalities in the local host species raised in aquaculture and destined for supplementation of the river system Loire-Allier was examined. The presence of N. salmonis was confirmed by PCR and histology in Salmo salar L. previously and in newly investigated salmonid species, Salmo salar, Salmo trutta fario L., Thymallus thymallus (L.) and Salvelinus alpinus (L.), present in European streams. The infection by N. salmonis was consistent in all cases with characteristic symptoms of the disease in deceased or moribund fish. The small subunit ribosomal DNA from N. salmonis was partially sequenced and compared to previously characterised N. salmonis isolates. As a result, a genotype, or clonal entity, was attributed to N. salmonis among Atlantic salmon found along the Northern Atlantic coastal lines and other salmonid species co-inhabiting or co-cultivated in the Auvergne region.     

The role of bacillus-based biological control agents in integrated pest management systems: plant diseases

ABSTRACT Bacillus-based biological control agents (BCAs) have great potential in integrated pest management (IPM) systems; however, relatively little work has been published on integration with other IPM management tools. Unfortunately, most research has focused on BCAs as alternatives to synthetic chemical fungicides or bactericides and not as part of an integrated management system. IPM has had many definitions and this review will use the national coalition for IPM definition: "A sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health and environmental risks." This review will examine the integrated use of Bacillus-based BCAs with disease management tools, including resistant cultivars, fungicides or bactericides, or other BCAs. This integration is important because the consistency and degree of disease control by Bacillus-based BCAs is rarely equal to the control afforded by the best fungicides or bactericides. In theory, integration of several tools brings stability to disease management programs. Integration of BCAs with other disease management tools often provides broader crop adaptation and both more efficacious and consistent levels of disease control. This review will also discuss the use of Bacillus-based BCAs in fungicide resistance management. Work with Bacillus thuringiensis and insect pest management is the exception to the relative paucity of reports but will not be the focus of this review.     

Towards the construction of a resistance risk evaluation scheme

Pesticide resistance management needs an indication of the risk of resistance developing in pests against pesticide applications. This paper describes an evaluation system for the ranking of these risks. The term pests includes all organisms which are causing economic damage in agriculture, including weeds and plant pathogens. The system distinguishes six broad risk categories. It is based on expert judgement of answers to a maximum of ten questions on crop husbandry, pest biology and pest control. The system has been developed for registration purposes in The Netherlands, and is currently being discussed within the European and Mediterranean Plant Protection Organisation (EPPO). ©1997 SCI     

玉米根萤叶甲的抗逆性与防治研究进展

玉米根萤叶甲（Diabrotica virgifera virgifera Leconte）在美国是最重要的玉米害虫。它不仅对一些环戊二烯、有机磷类和氨基甲酸盐类化学杀虫剂产生了很强的抗药性,还对玉米 大豆轮作和调整播期等农业防治措施产生了适应性。此外,该虫有较广的适生性和扩展性。在过去的60年内,它从美国中西部传到了东北部沿海地区,并入侵欧洲定殖为害。新近采用的防治方法主要是种植转Bt基因抗虫玉米。表达经生物工程改良并导入的某个Bt毒素基因如Cry3Bb1、Cry34Ab1/Cry35Ab1或mCry3A的转基因抗虫玉米可毒杀取食的玉米根萤叶甲。但在转Bt基因玉米使用数年后,田间观察和温室筛选研究显示,玉米根萤叶甲具有对转基因玉米的潜在抗性。本文对该叶甲与防治有关的生物学特性、抗逆性及其机制、防治措施做了综述和讨论,旨在对该害虫的检疫防除有所帮助。     

Sea louse control in Scotland,past and present

Methods for farming the Atlantic salmon (Salmo salar L) in Scotland were developed at the Unilever Research Laboratory facility at Lochailort on the west coast of Scotland in the late 1960s. By the spring of 1972 a fledgling commercial company had been set up and Marine Harvest, as it was known, received its first year class of smolts at Lochailort. Sea lice (Lepeophtheirus salmonis Kr?yer) from passing wild fish infected the smolts but did not cause any significant damage until the summer of 1976 when intervention was required. The Scottish industry has since grown to become a vital source of employment for fragile rural economies and produced about 130,000 tonnes of salmon in 2000. This paper gives an overview of how fish welfare has been maintained by the development of treatments and management strategies aimed at minimising the impact of sea lice.     

Resistance management in Europe: a preliminary proposal for the determination of a minimum number of active substances necessary to manage resistance

The evolution of resistance to plant protection products (PPPs) is an increasing management challenge that relates to both an increasing number of species and a limited number of active substances. The number of available active substances (a.s.) has decreased considerably over the past two decades, increasing the gravity of the resistance problem. Managing the threat of resistance is based on a reasoned choice of a.s., their sequence and combination. No quantitative information is available on how many different PPPs are needed for a sustainable control system of a given pest. This paper provides a first expert judgement‐based attempt at estimating the number of different a.s. necessary for sustainable control of a pest in which the evolution of resistance is prevented.     

Frankliniella occidentalis (Pergande) integrated pest management programs for fruiting vegetables in Florida

BACKGROUND: The spread of the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), resulted in the worldwide destabilization of established integrated pest management programs for many crops. Efforts to control the pest and the thrips‐vectored tospoviruses with calendar applications of broad‐spectrum insecticides have been unsuccessful. The result has been a classic ‘3‐R’ situation: resistance to numerous insecticides; resurgence of the western flower thrips populations as a result of natural predators and native competitor thrips being eliminated; replacement by various other pests. This paper reports on integrated pest management programs for fruiting vegetables that are effective, economical, ecologically sound and sustainable. RESULTS: The components include the following: define pest status (economic thresholds); increase biotic resistance (natural enemies and competition); integrate preventive and therapeutic tactics (scouting, ultraviolet‐reflective technologies, biological control, compatible insecticides, companion plants and fertility); vertically integrate the programs with other pests; continually communicate latest science‐based management tactics with end‐users. CONCLUSION: These programs have been widely implemented in Florida and have significantly improved the management of western flower thrips and thrips‐transmitted viruses. Copyright © 2012 Society of Chemical Industry     

Semiochemical strategies for sea louse control: host location cues

The development of behavioural bioassays and electrophysiological recording techniques has enabled the role of semiochemicals to be investigated for the first time in Lepeophtheirus salmonis (Kr?yer). Adult male sea lice L salmonis were activated by, and attracted to, salmon-conditioned water (SCW) and SCW extract. Non-host fish odours, turbot-conditioned water (TCW) and turbot-conditioned water extract (TCW extract), elicited activation but no attraction in the lice. Solid-phase extraction techniques were developed to extract low molecular weight components of fish odours, and biological activity was shown to be confined to these. Electrophysiological activity from aesthetascs in the first antennae was found and neural responses to odours were recorded from the antennal nerves. Preliminary experiments on individual chemicals (isophorone, 1-octen-3-ol) linked to salmon revealed behavioural activation and electrophysiological responses in adult male L salmonis. Isophorone was shown to be significantly attractive to sea lice when placed in a slow-release system in a perfused tank of seawater in a choice situation. Proof of concept has been established for successfully extracting odour cues from seawater, analysing their biological activity and applying these to slow-release technologies for field trapping of lice. Future work involving linked GC-MS techniques using behaviour, electrophysiological responses, and organolepsis will establish further host location cues specific to Atlantic salmon.     

A review of research to address carrot fly (Psila rosae) control in the UK1

Carrot fly (Psila rosae) is a serious pest of umbelliferous crops such as carrot, parsnip, celery and parsley. Carrot fly has been studied in the UK for more than 60 years. Whilst some of these studies have been focused on insecticides, others have demonstrated the potential for non‐insecticidal methods of control that might contribute to an integrated pest management strategy. These include rotation and spatial separation of susceptible crops; carrot varieties with partial resistance to carrot fly; and crop management strategies to avoid oviposition or the development of severe damage. This paper outlines some of the approaches that have been taken and indicates how these are, or might be, used in practice.     

Quantitative and qualitative analysis of accidental insect pest introduction into Switzerland and its implications for plant protection1

The purpose of this study is to assess the characteristics of accidental introduction of pest organisms into Switzerland by means of international plant trade, and to discuss its consequences for the development of plant protection strategies. We found substantial levels of infestation in samples of all producing countries included in the study. Since the use of synthetic pesticides is the main basis of pest control in the ornamental industry, the results of this study indicate that chemical pest control has reached a limit above which no further reduction of pest population levels is possible. The increased pesticide tolerance of many arthropod pests is mainly due to increased levels of resistance to pesticides caused by their excessive use. Therefore, alternative methods supplementing pesticide use are required to develop an optimal pest management strategy for the future. It is proposed that, in the Swiss ornamental production industry, pest monitoring should be the first step in this direction.     

Ecological pest management and control by using allelopathic weeds (Ageratum conyzoides,Ambrosia trifida,and Lantana camara) and their allelochemicals in China

The development of pest management and control is striving toward a future of sustainable agriculture. Weeds cause serious problems in agricultural ecosystems and attempts to control them have met with limited success. However, many weeds are allelopathic; that is, they can produce and release allelochemicals to interact with other plant competitors and to attack microbes or insect and other animal predators. These allelopathic weeds and their allelochemicals may be put into use for ecological pest management and control or employed for other uses. Currently, little attention has been paid to how allelopathic weeds and their allelochemicals potentially can be utilized as an important part of pest management and control in agricultural ecosystems. This review outlines recent research regarding the potential for pest management and control by allelopathic weeds and their allelochemicals by studying the cases of Ageratum conyzoides, Ambrosia trifida, and Lantana camara and provides examples of allelopathic weeds and their allelochemicals that have been incorporated into ecological pest management and control in China.     

Problem Identification and Knowledge Acquisition for the Solution of Pest Problems: A Suggestion for a Comprehensive Approach

The reduction of pre- and post-harvest yield losses due to pest attack represents a substantial contribution to the increase in food supply which will be absolutely essential in future. Not only must more food be produced but, in addition, this must be accomplished in an ecologically, economically and socially sustainable manner in a broader concept of food security improvement and poverty alleviation. Integrated pest management can play a key role in this process. Firstly, constraints and anticipated global food production requirements are presented in an overview. This is followed by a discussion of the various knowledge acquisition techniques for identifying and eliminating knowledge gaps with a view to solving pest problems in a systematic manner. It is concluded that the development of better integrated approaches based on an expanding theoretical, methodological and empirical basis will produce solutions which are more effective, sustainable and competitive compared with the currently prevailing procedures for pest problem solution.     

Microbiome facilitated pest resistance: potential problems and uses

Microbiome organisms can degrade environmental xenobiotics including pesticides, conferring resistance to most types of pests. Some cases of pesticide resistance in insects, nematodes and weeds are now documented to be due to microbiome detoxification, and is a demonstrated possibility with rodents. Some cases of metabolic resistance may have been misattributed to pest metabolism, and not to organisms in the microbiome, because few researchers use axenic pests in studying pesticide metabolism. Instances of microbiomes evolving pesticide resistance contributing to resistance of their hosts may become more common due the erratic nature of climate change, as microbiome populations typically increase and evolve faster in stressful conditions. Conversely, microbiome organisms can be engineered to provide crops and beneficial insects with needed resistance to herbicides and insecticides, respectively, but there has not been sufficient efficacy to achieve commercial products useful at the field level, even with genetically engineered microbiome organisms. © 2017 Society of Chemical Industry     

Pyrethroid resistance discovered in a major agricultural pest in southern Australia: the redlegged earth mite Halotydeus destructor (Acari: Penthaleidae)

BACKGROUND: The redlegged earth mite (Halotydeus destructor Tucker) is an important pest of field crops and pastures. Control of this pest relies heavily on chemicals, with few genuine alternatives presently available. Pesticide responses of H. destructor from the field with reported chemical control failures were compared with mites from susceptible 'control' populations. Toxicology bioassays were conducted on adult mites across multiple generations. RESULTS: Very high levels of resistance to two synthetic pyrethroids, bifenthrin and alpha-cypermethrin, were detected in this species for the first time. For bifenthrin, LC(50) estimates showed a difference in resistance of greater than 240 000-fold. Resistance to alpha-cypermethrin was almost 60 000-fold. This resistance was shown to be heritable, persisting after several generations of culturing. There was no evidence that resistance to organophosphorus chemicals had evolved, which is likely to be a direct consequence of the history of chemical applications these mites have experienced. CONCLUSION: These results highlight the need for more judicious management decisions in order to control pest species in a sustainable manner. The implications of these findings in regard to the management and future research of the redlegged earth mite are discussed.     

Advocating a need for suitable breeding approaches to boost integrated pest management: a European perspective

Currently, European farmers do not have access to sufficient numbers and diversity of crop species/varieties. This prevents them from designing cropping systems more resilient to abiotic and biotic stresses. Crop diversification is a key lever to reduce pest (pathogens, animal pests and weeds) pressures at all spatial levels from fields to landscapes. In this context, plant breeding should consist of: (1) increased efforts in the development of new or minor crop varieties to foster diversity in cropping systems, and (2) focus on more resilient varieties showing local adaptation. This new breeding paradigm, called here ‘breeding for integrated pest management (IPM)’, may boost IPM through the development of cultivars with tolerance or resistance to key pests, with the goal of reducing reliance on conventional pesticides. At the same time, this paradigm has legal and practical implications for future breeding programs, including those targeting sustainable agricultural systems. By putting these issues into the context, this article presents the key outcomes of a questionnaire survey and experts' views expressed during an EU workshop entitled ‘Breeding for IPM in sustainable agricultural systems’. © 2017 Society of Chemical Industry