Agricultural nematology in East and Southern Africa: problems,management strategies and stakeholder linkages

By 2050, Africa's population is projected to exceed 2 billion. Africa will have to increase food production more than 50% in the coming 50 years to meet the nutritional requirements of its growing population. Nowhere is the need to increase agricultural productivity more pertinent than in much of Sub‐Saharan Africa, where it is currently static or declining. Optimal pest management will be essential, because intensification of any system creates heightened selection pressures for pests. Plant‐parasitic nematodes and their damage potential are intertwined with intensified systems and can be an indicator of unsustainable practices. As soil pests, nematodes are commonly overlooked or misdiagnosed, particularly where appropriate expertise and knowledge transfer systems are meager or inadequately funded. Nematode damage to roots results in less efficient root systems that are less able to access nutrients and water, which can produce symptoms typical of water or nutrient deficiency, leading to misdiagnosis of the underlying cause. Damage in subsistence agriculture is exacerbated by growing crops on degraded soils and in areas of low water retention where strong root growth is vital. This review focuses on the current knowledge of economically important nematode pests affecting key crops, nematode control methods and the research and development needs for sustainable management, stakeholder involvement and capacity building in the context of crop security in East and Southern Africa, especially Kenya, Tanzania, Uganda and Zimbabwe. © 2015 Society of Chemical Industry     

How well will stacked transgenic pest/herbicide resistances delay pests from evolving resistance?

Resistance has evolved to single transgenic traits engineered into crops for arthropod and herbicide resistances, and can be expected to evolve to the more recently introduced pathogen resistances. Combining transgenes against the same target pest is being promoted as the solution to the problem. This solution will work if used pre‐emptively, but where resistance has evolved to one member of a stack, resistance should easily evolve for the second gene in most cases. We propose and elaborate criteria that could be used to evaluate the value of stacked traits for pest resistance management. Stacked partners must: target the same pest species; be in a tandem construct to preclude segregation; be synchronously expressed in the same tissues; have similar tissue persistence; target pest species that are still susceptible to at least two stacked partners. Additionally, transgene products must not be degraded in the same manner, and there should be a lack of cross‐resistance to stacked transgenes or to their products. With stacked herbicide resistance transgenes, both herbicides must be used and have the same persistence. If these criteria are followed, and integrated with other pest management practices, resistance may be considerably delayed. © 2016 Society of Chemical Industry     

中国应对草地贪夜蛾入侵研究的主要进展

草地贪夜蛾Spodoptera frugiperda(J. E. Smith)是严重威胁我国粮食生产的重大入侵性害虫。自2019年草地贪夜蛾入侵我国以来,我国植保工作者在其生物学和发生规律、迁飞与种群监测、生态调控和理化诱控、生物防治和化学防控技术等方面取得一系列重要进展：基本明确了草地贪夜蛾在我国的发生规律,建立了以监测预警、生物防治、理化诱控和应急化学防控为一体的草地贪夜蛾综合防控技术体系。本文综述了草地贪夜蛾在我国的总体研究概况及在灾变和治理研究中取得的主要进展,并展望了农民接受、社会认可、生态可持续的草地贪夜蛾安全治理工作,以期为提升我国草地贪夜蛾的安全治理能力提供有力的科技支撑。     

Ecological aspects of pest risk assessment1

The primary purpose of a national plant protection organization is to prevent the spread of quarantine pests. Such pests are characterized according to their predicted capability to be of economic importance in new areas. The determination of the potential of an exotic pest to cause crop losses is a preliminary component in a pest risk assessment (PRA) process. The initial PRA step includes two distinct ecological analyses. The first must predict the expected extent and frequency to which a new pest population will attain and/or surpass the economic injury level. This is necessary to justify the classification of an exotic pest as being of quarantine significance. Secondly, a PRA must estimate the likelihood of establishment for those quarantine pests for which an entry pathway exists. Both require that bioclimatic comparisons be made between the areas of origin and distinct target destinations. The bioclimatic methodologies of the past are currently being enhanced to specify more precisely‘quarantine pest zones of ecological equivalency’, i.e. areas within which the behavior of a specific quarantine pest can be expected to be the same. The information derived from studies that provide a basis for forecasting the behavior of indigenous pests can also be used in PRA.     

Some Opportunities for Pest Prevention by Ultra-low Volume Spraying

The needs of the modern system of integrated control, or pest management, are contrasted with those of the prevailing view that pest control is an individual responsibility. It is argued that a rational approach to pest management must be based on a knowledge of the scale on which it must be exercised. In the case of mobile insects the scale normally far exceeds the ecologically artificial boundaries represented by fields or private holdings. The argument is illustrated by the desert locust where numbers are reckoned in millions of millions and mobility in terms of hundreds and thousands of km., calling for international action, and the Tsetse fly where numbers are reckoned in less than 10 per ha. and mobility in terms of km. Experience in the control of paddy pests in Java is drawn on to show the contribution of synoptic survey to delimit the scale and time for appropriate action, followed by synchronous application of pesticides in achieving, through control of pests, yield increases in excess of what could be expected from small scale plot trials. The value of spraying at ultra-low volume rates is that it provides the means of achieving more or less synchronous application of pesticides on the scale demanded by the problem.     

Factors in the Success and Failure of Microbial Control in Turfgrass

Turfgrass is an important component of urban landscapes and turf associated products and services are valued at about $45 billion in the US alone. Turf insecticide market is about $500 million per year of which microbial insecticides constitute less than 0.1%. Major factors in the poor market penetration of microbial insecticides include low damage thresholds, narrow spectrum of activity, a definite pest monitoring requirement, shortage of quality products, and competition with the newly registered less-toxic chemical insecticides. Enhancement of market share of microbial insecticides in turf will depend upon successful development of more appropriate application strategies, an increase in the availability of quality products, and the development of a systems approach in which microbial insecticides are used together with chemical insecticides in a more compatible manner. The long-term benefits derived from the use of microbial insecticides must be documented to enhance acceptance of microbial control.     

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.     

Sampling plans,selective insecticides and sustainability: the case for IPM as ‘informed pest management’

Integrated Pest Management (IPM) is considered the central paradigm of insect pest management and is often characterized as a comprehensive use of multiple control tactics to reduce pest status while minimizing economic and environmental costs. As the principal precursor of IPM, the integrated control concept formulated the economic theory behind pest management decisions and specified an applied methodology for carrying out pest control. Sampling, economic thresholds and selective insecticides were three of the critical elements of that methodology and are now considered indispensable to the goals of IPM. We examine each of these elements in the context of contemporaneous information as well as accumulated experience and knowledge required for their skillful implementation in an IPM program. We conclude that while IPM is principally about integrating control tactics into an effective and sustainable approach to pest control, this overarching goal can only be achieved through well‐trained practitioners, knowledgeable of the tenets conceived in the integrated control concept that ultimately yield informed pest management. Copyright © 2009 Society of Chemical Industry     

There has never been a better time or a greater need for resistance management

Integrated pest management (IPM) and sustainable agriculture benefit from selective and environmentally benign crop-protection products. The performance of these products, however, is threatened by resistance. If it is to be prevented from standing in the path of progress, resistance must be managed. As agricultural practices move towards IPM and sustainable crop protection, selection pressure will be concentrated on products which are compatible with these systems. Producers, researchers, government and extension workers cannot solve these complex problems alone. The key to success is collaboration. The Insecticide Resistance Action Committee (IRAC) was set up by the crop-protection industry in 1984 to promote and co-ordinate its contribution to resistance management. Today, it is collaborating with research institutes, government organisations and extension services to combat resistance. IRAC focuses on research and communication projects which reduce selection pressure, organising workshops in ‘resistance hot spots’ and providing input to draft legislation. Selected examples of IRAC's collaborative work are described. ©1997 SCI     

Botanical insecticides: for richer, for poorer

Botanical insecticides presently play only a minor role in insect pest management and crop protection; increasingly stringent regulatory requirements in many jurisdictions have prevented all but a handful of botanical products from reaching the marketplace in North America and Europe in the past 20 years. Nonetheless, the regulatory environment and public health needs are creating opportunities for the use of botanicals in industrialized countries in situations where human and animal health are foremost--for pest control in and around homes and gardens, in commercial kitchens and food storage facilities and on companion animals. Botanicals may also find favour in organic food production, both in the field and in controlled environments. In this review it is argued that the greatest benefits from botanicals might be achieved in developing countries, where human pesticide poisonings are most prevalent. Recent studies in Africa suggest that extracts of locally available plants can be effective as crop protectants, either used alone or in mixtures with conventional insecticides at reduced rates. These studies suggest that indigenous knowledge and traditional practice can make valuable contributions to domestic food production in countries where strict enforcement of pesticide regulations is impractical.     

Global developments in biological control and the implications for Europe1

Developed and developing countries, for a range of reasons, have strongly endorsed an IPM approach to sustainable pest management. IPM is founded on the self-renewing contribution of natural enemies to pest suppression, or biological control. However, many pests today escape such natural control because they are exotic introductions, and for these pests the introduction of specific biological control agents is a proven and valuable technique. With growing exotic pest problems in agriculture and forestry, due both to increased trade and to the policy of the WTO, with new concern for exotic invasive species affecting biodiversity, and with a booming biocontrol industry, there is a rapid growth of interest in introduced biological control agents (including biopesticides, which are generally still not acknowledged as introductions). To meet this demand for biological control introductions, it is necessary to address issues of research, safety and the rights of governments and peoples to their genetic resources. By and large, Europe has not done this, and this is proving both an opportunity for environmental accidents and a disincentive for sustainable agriculture and conservation.     

Assessing Risks from Exotic Pests1

Detailed assessment of the potential of an alien species to become a pest when introduced into a new area requires a comprehensive knowledge of the biology of that species. In the absence of such knowledge, species can be classified for temperate areas into one of four categories of risk on the basis of capacity for survival in similar climates and presence of host plants outdoors or under glass. The categories are: 1) potential outdoor pests, 2) potential glasshouse pests, 3) species that have outdoor hosts but are unlikely to become pests on them unless they adapt genetically (no hosts under glass), and 4) species that have no host plants outdoors or under glass, or are incapable of prolonged survival outdoors. Some aspects of the more detailed assessment of better known species are suitable for computer simulation modelling. The features of a phenological model currently being developed in England are briefly described. Estimates of the benefits derived from excluding a particular alien pest can be obtained from the cost of the additional annual control measures likely to be required if the pest were to be introduced. Estimates of factors such as crop losses, environmental problems and increased research and advisory work must be added to obtain a range of costs for years when pest populations are likely to be ← high →, ← normal → and ← low →. Costs of excluding the pest must include cost to government (staff costs, eradication measures, publicity etc.) and costs to industry. The resulting comparison of benefit with cost can aid decisions on the design and enforcement of phytosanitary regulations.     

Plant pest introductions and their spread: call for action or just watch? An African perspective

Pest introductions and the spread of pests in Africa have caused serious economic consequences (both direct and indirect) in many different countries in recent decades. Unintentional pest introductions, if not addressed, will continue to devastate individuals’ livelihoods, endanger national food security and damage the economy due to negative effects on export, which could include banning the exports of certain crops/products. Regulatory authorities are key to minimizing these pest introductions and their spread. These authorities need to become proactive and ask questions such as why this is happening, what potential actions can be taken as intervention strategies to stop/reduce pest invasions and how can spread be reduced? Several potential actions are possible but this paper narrows these down to (1) capacity building for national plant protection organizations (NPPOs), (2) public–private partnership and cooperation, and (3) investment in research for data collection and models for pest predictions. Information on these actions is given considering the situation in Africa. African countries are at high risk of pest introduction, potential losses of food and limitations to market access. NPPOs need to act now to minimize the risks and ensure food and environmental safety.     

Resistance to foliage-feeding insects in conifers: implications for pest management

The ecological implications of insect resistance in conifers are rarely discussed. It is however a fairly straightforward plant-insect interaction and should be treated as such, making use of the increasing amount of information in this field. Work on tree breeding is usually carried out by silviculturalists who, not surprisingly, rarely consider the insect component of the environment in which the treess are growing. In all fairness, it must be stated that many entomologists, fail to consider the plant component of the interaction. Clonal forestry will almost certainly result in the loss of genetic variability. The use of clonal material has already been cited as a possible source for the diminution of the resistance against pests and diseases and if particular resistance mechanisms against forest pests are sought in the future the reduction in genetic material caused by clonal selection could have serious consequences. The ethics of clonal forestry have been questioned as have the ethics of biotechnological advances in the area of recombinant DNA molecules. The potential of both these techniques should be publicized and brought to the attention of the general public and the scientific community at large and evaluated. To improve our forest environment and to protect the environment as a whole, entomologists, geneticists, physiologists and silviculturalists must work together to produce better trees that require little, if any, chemical aid, be it insecticides, herbicides, fungicides or fertilizers. An increasing awareness of the environmental problems generated by large-scale insecticide applications to forest plantations, coupled with an increasingly chemophobic work-force and the difficulty in obtaining pesticide registration for use in forest environments, means that the forest industry world-wide must look to the use of integrated control measures with more diligence than has been shown in the past. Many recent outbreaks of pests and diseases have been linked with particular seed origins of tree crops. Host plant resistance as part of a suite of other proposed integrated control tools is thus an obvious candidate for development. Despite this, scientists concerned with tree improvement continue to select largely for silvicultural traits rather than for resistance to pests and disease. The different avenues open to plant breeders are examined and the potential of breeding trees resistant to insect attack highlighted. Using resistant trees as part of an integrated pest management system has five very important properties. Firstly, there is no additional pest control cost to the grower, secondly, it operates at all levels of insect incidence and not just when the pest is at high population levels, thirdly, it reduces the insect population cumulatively, fourthly it avoids toxic residues and environmental pollution and, finally, it usually interacts well with the other integrated pest management strategies in existence.     

Plant Protection and Production in Modern Society1

Many currently existing agricultural production techniques have been developed in total reliance on effective chemical pest control. Today, however, it is becoming clear that chemical pest control has a number of limitations, and its ever increasing costs may well make it a limiting factor in agricultural production. This has already occurred in a number of cotton growing areas. The need for increased world food production will require improved pest control methods. If no special precautions are taken, we will undoubtedly end up in many other crops with a situation similar to that of cotton. In view of the reduced availability of new pesticides, those currently available should be used in the optimal way. At the present time, the integrated pest control approach is the best means of accomplishing this. The introduction of such programs will require official support through legislation or technical assistance. In the future, various new developments in pest control are to be expected. Greater reliance will be placed on the use of computer science. Further effort will be needed in areas such as crop loss assessment, stored product pests, technical assistance to farmers and pesticide selectivity. Closer international collaboration on plant quarantine matters and pesticide registration are essential for the future of pest control.     

Monitoring of Pear Psylla for Pest Management Decisions and Research

Pear psylla, Cacopsylla pyricola (Foerster) (Homoptera: Psyllidae), is one of the key insect pests in North American pear production. In some growing areas, more than 50% of dollars spent to control arthropod pests in commercial pear are directed specifically at controlling this species. Control measures require accurate and timely information about dispersal, onset of egg-laying in spring, densities in the orchard, and age composition of the population. To meet these ends, a number of sampling methods have been developed to monitor pear psylla, the most common being (for pest management purposes) visual inspection of spurs and foliage for nymphs and eggs, and use of beat trays to monitor adults. Action thresholds have been developed for counts obtained with either method. However, threshold estimates are fairly narrowly defined, referring to a somewhat limited group of pear cultivars, type of injury to be prevented, and pest management program being used. Further refinement has been difficult because of an incomplete understanding of psylla's spatial distribution, seasonal changes in spatial distribution, and unknown or seasonally changing action thresholds. Beat trays and visual inspection of foliage have also been used to monitor pear psylla in various types of research projects, including studies of dispersal and biological control. Other sampling tools used in research include sticky traps, suction traps, and water pan traps. Density estimates obtained by these different sampling methods tend be positively correlated, albeit with high levels of unexplained variation. For counts obtained by sticky traps, much of the unexplained variation can be attributed to flight activity of the insect, which is known to depend (at a minimum) on sex, morphotype, reproductive status, time of year, time of day, leaf fall, and weather. Thus, if sticky traps are to be used in a pest management program for pear psylla, it must be recognized that counts on traps will include both density and (potentially large) behavioral components. I conclude this review with suggestions about the type of research that would improve monitoring techniques for this pest and assist eventually in developing a more effective control program.     

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry     

Integrated pest management of coffee for small-scale farmers in East Africa: needs and limitations

Coffee in East Africa (Kenya, Tanzania and Uganda) is an important cash and export crop for small-scale farmers. The crop suffers heavy yield losses due to damage caused by a wide range of indigenous pests (insects, diseases, nematodes and weeds). Current recommended pest control measures include a combination of cultural, resistant/tolerant cultivars and the use of broad spectrum chemical pesticides. Chemical pesticides are far more popular at the farm level than any of the other recommended pest control measures. Coffee pest control strategies are often aimed at individual pests with little consideration of the implications for the total coffee pest complex and its agro-ecosystem. This unilateral approach has resulted in increased pest pressure on coffee and some of its companion crops, outbreak of new pests of coffee, development of pest strains resistant to the cheap and commonly available chemical pesticides, increased environmental problems, increased health risks to man and livestock and an overall increase in the costs of coffee production, thus forcing many farmers to neglect their coffee plantations. Measures to alleviate the above problems, particularly the high production costs, are needed to improve coffee production and increase the cash return to the small-scale farmer. Integrated pest management (IPM) offers the best prospects for solving the above problems. However, lack of national IPM policies, poor extension systems, inefficient research-extension-farmer linkage and the lack of a holistic approach will delay the development and implementation of appropriate, acceptable and sustainable IPM practices.     

United States Department of Agriculture-Agricultural Research Service research on managing insect resistance to insecticides

Insecticide resistance has developed within many classes of pesticide, and over 500 species of insects and mites are resistant to one or more insecticides. Insecticide resistance and the consequent losses of food and fiber caused by failure to control insect and mite pests causes economic losses of several billion dollars worldwide each year. It is the goal of insect resistance management (IRM) to preserve useful pesticides by slowing, preventing or reversing development of resistance in pests. Important aspects of this goal are understanding the development of resistance and monitoring to determine ways to prevent its development. We describe programs specific to missions of the US Department of Agriculture, Agricultural Research Service, which are designed to characterize insecticide resistance in insects and mites with the goal of managing pests in an ecologically acceptable manner. Resistance management of cotton, potatoes, vegetables, melons, ornamentals, greenhouse crops, corn, stored grains, livestock, honeybees and mites, as well as management of transgenic crops are evaluated. We conclude that IRM is a vital part of stewardship of any pest management product and must be a combined effort of manufacturers, growers, consultants, extension services and grower organizations, working closely with regulators, to achieve logistically and economically feasible systems that prolong the effectiveness of all pest-control products.     

A philospohy of pest control —A biological approach to new pesticide developments

The influences on pest control that are external to the pesticide industry are discussed first. The complexity of the interrelationship between the five main parties to the pesticide controversy (the farmer, the public, the pesticide manufacturer, wild life interests and the government) explains in some measure the intensity of the controveersy itself. It is to be hoped that with increasing knowledge all parties will be able to move together along an agreed, optimum course.The responses within pest control in general, and the pesticide industry in particular, to these external influences are then discussed. Existing pest control practices largely utilise control at the level of the individual. Much current research relates to population control procedures. The pesticide industry is concerned with innovations relating to the mode of action of conventional insecticides as well as to new ways of using chemicals to control insect populations. It is suggested the long term success of population control procedures depends as much on the provision of appropriate organisasuccess of population control procedures depends as much on the provision of appropriate organisational requirements as on solving the technical problems.Finally, the likely future couse of pest control is considered. It is suggested that over the next 10 years or more the major burden of pest control will continue to fall on the pesticide industry much as at present. The first innovations, over the period 5–15 years hence, are likely to concern conventional pesticides with novel modes of action. Population control procedures will gradually become established and this process will accelerate over the period 10–20 years hence and beyond. However, full benefit from such procedures will only accrue if organisatonal requirements have been met.