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Schistocerca gregaria (desert locust)
Abstract
The desert locust, Schistocerca gregaria (Forskål), is one of about a dozen species of short-horned grasshoppers that can form dense, mobile adults’ swarms or huge hopper bands. Desert locust probably is the oldest and most dangerous migratory pest globally, affecting up to 60 countries in Africa, the Middle East and South West Asia. Magnitude of plagues and destruction they cause are due to exceptional gregariousness, mobility, voracity and size of swarms. Sudden and severe damage can be caused to a wide variety of crops. The outbreaks can result in substantial effects on national and regional food security and agricultural and agropastoral livelihoods when they reach upsurge or plague levels. In addition, social costs to the local human population during outbreaks can be enormous, but difficult to estimate. For decades, a preventive control strategy has been implemented under the aegis of the United Nation’s Food and Agriculture Organization (FAO) in Rome, Italy. This strategy aims to intervene early against localized outbreaks before plague status is reached, thus limiting the amount of pesticides used. This strategy is constantly being improved to take advantage of the latest technologies in communications, geographic information systems, satellite remote sensing, drones, models and early warning systems. FAO operates a centralised Desert Locust Information Service to monitor weather, ecological conditions and locust situation on a daily basis to assess current situation and forecast timing, scale and location of breeding, gregarization and migration up to six weeks in advance. Locust survey and control are primarily the responsibility of locust affected countries and are operations undertaken by national locust units. Several regional locust organizations also assist with survey and control operations. The effectiveness of this strategy has been proven for several decades, significantly reducing the frequency and magnitude of invasions since the 1960s. However, a number of challenges remain to make the control of this pest more efficient, sustainable and environmentally friendly.
This datasheet on Schistocerca gregaria covers Identity, Overview, Distribution, Hosts/Species Affected, Diagnosis, Biology & Ecology, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.
... However, when the stressor diminishes or disappears, the phenotype of not just the individual but potentially the whole population will "spring back" to the original phenotype ( Figure 5). An extreme example of rapid phenotypic change and rebound occurs in the desert locust, Schistocerca gregaria, found in Africa, the Middle East and Southeast Asia (Lecoq, 2022). In the absence of rain, individual locusts exist in a behaviorally solitary state, with typically green coloration. ...
Animals from embryos to adults experiencing stress from climate change have numerous mechanisms available for enhancing their long-term survival. In this review we consider these options, and how viable they are in a world increasingly experiencing extreme weather associated with climate change. A deeply understood mechanism involves natural selection, leading to evolution of new adaptations that help cope with extreme and stochastic weather events associated with climate change. While potentially effective at staving off environmental challenges, such adaptations typically occur very slowly and incrementally over evolutionary time. Consequently, adaptation through natural selection is in most instances regarded as too slow to aid survival in rapidly changing environments, especially when considering the stochastic nature of extreme weather events associated with climate change. Alternative mechanisms operating in a much shorter time frame than adaptation involve the rapid creation of alternate phenotypes within a life cycle or a few generations. Stochastic gene expression creates multiple phenotypes from the same genotype even in the absence of environmental cues. In contrast, other mechanisms for phenotype change that are externally driven by environmental clues include well-understood developmental phenotypic plasticity (variation, flexibility), which can enable rapid, within-generation changes. Increasingly appreciated are epigenetic influences during development leading to rapid phenotypic changes that can also immediately be very widespread throughout a population, rather than confined to a few individuals as in the case of favorable gene mutations. Such epigenetically-induced phenotypic plasticity can arise rapidly in response to stressors within a generation or across a few generations and just as rapidly be “sunsetted” when the stressor dissipates, providing some capability to withstand environmental stressors emerging from climate change. Importantly, survival mechanisms resulting from adaptations and developmental phenotypic plasticity are not necessarily mutually exclusive, allowing for classic “bet hedging”. Thus, the appearance of multiple phenotypes within a single population provides for a phenotype potentially optimal for some future environment. This enhances survival during stochastic extreme weather events associated with climate change. Finally, we end with recommendations for future physiological experiments, recommending in particular that experiments investigating phenotypic flexibility adopt more realistic protocols that reflect the stochastic nature of weather.
Since ancient times, locusts have been serious pests wreaking havoc on settled agriculture throughout much of the world. Numerous locust practices have been developed to control infestations. This has led to most commentaries portraying locust infestations only in a negative light while focusing on finding best management practices for suppressing locust populations and lessening crop damage caused by swarms. Yet, locusts are also of great ecological significance in being not only an extraordinary natural phenomenon but also major components of ecosystem nutrient cycling, arising long before settled agriculture. Furthermore, for humans, locusts are a nutritious food source, historically and currently being consumed directly. Locust control today should more regularly include their harvesting. This is now more feasible, as environmentally friendly biopesticides can be used to replace harmful organic pesticides. We focus here on the ecological significance of locusts by using calculations based on a 1 km 2 area of swarming and breeding Desert locusts, Schistocerca gregaria, and show that the huge biomass of locust individuals contributes greatly to ecosystem processes while also having great potential use in human nutrition, especially where there is an urgent need for improved dietary intake and nutrition.
Locust outbreaks have impacted agricultural societies for millennia, they persist today, and humans aim to manage them using preventative strategies. While locusts have been a focus for natural sciences for more than a century, social sciences remain largely underrepresented. Yet, organizational, economic, and cultural variables substantially impact these management strategies. The social sciences are one important means through which researchers and practitioners can better understand these issues. This paper examines the scope and purpose of different subfields of social science and explores how they can be applied to different issues faced by entomologists and practitioners to implement sustainable locust research and management. In particular, we discuss how environmental governance studies resonate with two major challenges faced by locust managers: implementing a preventative strategy over a large spatial scale and managing an intermittent outbreak dynamic characterized by periods of recession and absence of the threat. We contend that the social sciences can help facilitate locust management policies, actions and outcomes that are more legitimate, salient, robust, and effective.
Effective locust and grasshopper control is crucial as locust invasions have seriously threatened crops and food security since ancient times. However, the preponderance of chemical insecticides, effective and widely used today, is increasingly criticized as a result of their adverse effects on human health and the environment. Alternative biological control methods are being actively sought to replace chemical pesticides. Nosema locustae (Synonyms: Paranosema locustae, Antonospora locustae), a protozoan pathogen of locusts and grasshoppers, was developed as a biological control agent as early as the 1980s. Subsequently, numerous studies have focused on its pathogenicity, host spectrum, mass production, epizootiology, applications, genomics, and molecular biology. Aspects of recent advances in N. locustae show that this entomopathogen plays a special role in locust and grasshopper management because it is safer, has a broad host spectrum of 144 orthopteran species, vertical transmission to offspring through eggs, long persistence in locust and grasshopper populations for more than 10 years, and is well adapted to various types of ecosystems in tropical and temperate regions. However, some limitations still need to be overcome for more efficient locust and grasshopper management in the future.
The desert locust has been a notorious pest since ancient times. A population upsurge hit Pakistan in 2019 and caused tremendous damage to agriculture and livelihoods. To take advantage of this ongoing upsurge, we conducted a field study to verify whether locust collection could be an interesting control method to protect crops in the event of an invasion, as well as an accepted food resource for poor rural communities. A village in the Thar desertic region was selected as a type-locality. An awareness campaign was launched to promote the collection and consumption of locusts as well as to alert people of their nutritional value. Two large swarms arrived near the village and several other swarms affected places nearby. Around 3033 kg of locusts were collected through handpicking at night. Most of the locusts were eaten and, as a result, hoppers of the next generation did not emerge in the type-locality; however, hopper bands appeared in areas where entomophagy was not practiced. The study area had less locust activity because swarms could not lay eggs due to entomophagy by the villagers. The consumption of desert locusts could be an effective practice to prevent malnutrition and protein deficiency and, to a certain extent, an efficient mitigation measure to help local populations to better protect themselves and their crops against locust outbreaks. Collection and consumption of locusts should be encouraged while remaining realistic about its real impact on locust control. This should also be done in concert with local authorities to take into account the risks to human health and to avoid the consumption of insects treated with pesticides.
Desert locust ( Schistocerca gregaria Forskål) is one of the most serious agricultural pests in the world due to its voracity, speed of reproduction, and range of flight. We discuss the current state of knowledge on its biological control using microorganisms and botanical extracts. Metarhizium flavoviride was among the first fungus to be recognized as a bio-control agent against desert locust in the laboratory and field conditions. Nevertheless, its oil formulation adversely affected non-target organisms, hence led to further research on other microorganisms. Metarhizium anisopliae var. acridum (syn. Metarhizium acridum ) is an environmentally safer bio-pesticide that has no measurable impact on non-target organisms. However, there are various shortcomings associated with its use in desert locust control as highlighted in this review. Bacterial pathogens studied were from species of Bacillus , Pseudomonas , and Serratia . Botanical extracts of 27 plant species were tested against the locust but showed varied results. Azadirachta indica and Melia volkensii were the most studied plant species, both belonging to family Meliaceae, which is known to have biologically active limonoids. Out of the 20 plant families identified, Apiaceae was the most represented with a frequency of 21%. However, only crude botanical extracts were used and therefore, the active ingredients against desert locust were not identified. Through a comprehensive research, an integrated pest management strategy that incorporates these bio-controls would be a realistic option to control desert locust infestations.
The desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), a major Old World pest, is associated with agricultural losses and undesirable societal effects. There are three broad approaches to its control: reaction, proaction, and outbreak prevention. Reaction protects crops from swarms but it is costly and disruptive. Proaction involves early intervention during outbreaks to avert further development to plague status; it is in current use because it is effective, relatively inexpensive, and it is the best available option for now. Outbreak prevention, largely unavailable since the 1970s, at least on a regional scale, will require highly sensitive surveillance to detect the onset of gregarization. Sufficiently early intervention can, hypothetically, extend desert locust recession indefinitely. While research on desert locust biology and behavior is, almost, no longer an urgent requirement to improve the efficacy of control, new priorities have arisen for developing outbreak prevention capability (and for enhancing proaction). Salient needs presently include long residual tactics for prophylactic (preventive) control in breeding areas, intervention thresholds, and improved, sustainable coordination among stakeholders at national, regional, and international levels. The most recent desert locust episode of 2020 provides an illustrative example of how prevention might have averted the entire upsurge, and how proaction in some countries contained the spread of swarms. The initial outbreak in Saudi Arabia escaped control due to unpreparedness, and impacts of armed conflict in Somalia and Yemen, which weakened surveillance and control, further contributed to the invasion of ≥22 countries, and the spraying of ≈4.9 million ha, by the end of 2020.
Despite many areas of progress in recent years, desert locust surveillance and control is impaired by many obstacles, the most intractable of which is insecurity. Insecurity involves rebellions, insurgencies, civil and international war, banditry, terrorism, and minefields. Obstruction of desert locust operations in breeding areas by ongoing armed conflict and landmines constitutes “direct” insecurity. “Indirect” insecurity, although less obvious, is arguably more broadly deleterious by debilitating government function and diverting funds, personnel, and equipment from desert locust management. Indirect “active” insecurity is armed conflict and civil unrest that is occurring at the same time as a desert locust episode, but not in the breeding areas. Indirect “inactive” insecurity refers to the after-effects of insecurity, including weak funding because of prior inattention to capacity maintenance during times of direct and indirect active insecurity, disabled or militarily-appropriated vehicles and other resources, destruction of infrastructure, and deployment of mines. We provide examples of direct and indirect insecurity across 35 years, from 1986 through May 2020, in 13 African and Asian countries (Chad, Eritrea, Ethiopia, India, Mali, Mauritania, Niger, Pakistan, Saudi Arabia, Somalia, Sudan, Western Sahara, and Yemen) with desert locust breeding areas to illustrate the complexity, pervasiveness, and chronic occurrence of insecurity. The upsurge of 2020 is used to show how direct insecurity still contributes to the genesis and expansion of desert locust episodes. Possible mitigation of direct insecurity effects on some desert locust operations is discussed.
Citation: Cheke, R.A.; Young, S.; Wang, X.; Tratalos, J.A.; Tang, S.; Cressman, K. Evidence for a Causal Relationship between the Solar Cycle and Locust Abundance. Agronomy 2021, 11, 69. https://doi.org/10.3390/agronomy11010069.
Dating population divergence within species from molecular data and relating such dating to climatic and biogeographic changes is not trivial. Yet it can help formulating evolutionary hypotheses regarding local adaptation and future responses to changing environments. Key issues include statistical selection of a demographic and historical scenario among a set of possible scenarios, and estimation of the parameter(s) of interest under the chosen scenario. Such inferences greatly benefit from (a) independent information on evolutionary rate and pattern at genetic markers; and (b) new statistical approaches, such as approximate Bayesian computation‐random forest (ABC‐RF), which provides reliable inference at a low computational cost and the possibility to measure prediction quality at the exact position of the observed data set. Here, we show full potential of the ABC‐RF approach including prior knowledge on microsatellite genetic markers to decipher the evolutionary history of the African arid‐adapted pest locust, Schistocerca gregaria, with support for a southern colonization of Africa, from a low number of founders of northern origin, dating back 2.6 Ky (90% CI: 0.9–6.6 Ky). We verify that this divergence time estimate accurately reflected true divergence time values by computing accuracy at a local posterior scale from simulated pseudo‐observed data sets. The inferred divergence history is better explained by the peculiar biology of S. gregaria, which involves a density‐dependent swarming phase with some exceptional spectacular migrations, rather than a continuous colonization resulting from the continental expansion of open vegetation habitats during more ancient Quaternary glacial climatic episodes.
GB - The Desert Locust, Schistocerca gregaria Forskål, 1775, is a major threat to agriculture. Refining our knowledge on its spatial distribution is a key point for its preventive management. To do so, we used in Chad a method of spatial smoothing of densities upon 7014 survey points (1965-1971 and 1986-2017) of the Desert Locust to develop seasonal distribution maps for invasion and remission periods. Three zones corresponding to breeding and gregarization areas have been identified: 1) Kanem/lake Chad, 2) Batha, 3) Ennedi. The first one may be a new gregarization area. These zones add to the Tibesti mountains where locust reports are less frequent than in the past, due to insecurity. More regular surveys should confirm that the distribution of the Desert Locust has recently changed. FR - Le criquet pèlerin Schistocerca gregaria Forskål, 1775, est un ravageur majeur pour l’agriculture. Affiner les connaissances sur sa distribution spatiale est essentiel pour sa gestion préventive. Dans ce but, nous avons utilisé au Tchad une technique de lissage spatial de densités sur 7014 observations du criquet pèlerin (1965-1971 et 1986-2017) afin d’élaborer des cartes saisonnières de répartition pour les périodes d’invasion et de rémission. Trois zones correspondant à des aires de reproduction et foyers de grégarisation ont été identifiées : 1) Kanem/lac Tchad, 2) Batha, 3) Ennedi. La première pourrait être un nouveau foyer de grégarisation. Ces zones se rajoutent à celle du massif du Tibesti, où les signalements sont plus rares que par le passé à cause de l’insécurité. Des prospections plus régulières devraient permettre de confirmer que la distribution du criquet pèlerin a récemment évolué.
Main useful information on the Desert Locust, a pest of great economic importance : identification and diagnosis, distribution, hosts plants, plant damage & economic impact, reproductive biology, management (biological, cultural and chemical control, early warning system, field monitoring), main information sources.
This encyclopedia covers the main Orthoptera species–locusts, grasshoppers and crickets–considered as important pests of crops and pasture worldwide. Some of these species are invasive at a continental scale. Their control is sometime critical to food security worldwide, requiring governmental or international involvement. This book–illustrated with more than 120 color photos–may be useful in identifying these pests, also providing biological and ecological data, as well as information on how to manage them in the framework of integrated pest management strategies. It will provide very various readers–academics, entomologists, farmers, researchers, extensionists–with key information on this group of insects of great economic importance.
Online sales worldwide available on the website of the Orthopterists' Society at: http://orthsoc.org/publications/books/
Locusts and grasshoppers (Orthoptera: Acridoidea) are among the most dangerous agricultural pests. Their control is critical to food security worldwide and often requires governmental or international involvement. Although locust and grasshopper outbreaks are now better controlled and often shorter in duration and reduced in extent, large outbreaks, often promoted by climate change, continue to occur in many parts of the world. While some locust and grasshopper control systems are still curative, the recognition of the damage these pests can cause and the socioeconomic consequences of locust and grasshopper outbreaks have led to an increasing paradigm shift from crop protection to preventive management. We are far now from a system of all-chemical control that D.L. Gunn wrote about in his review in 1960 (Annu. Rev. Entomol. 5:279–300). Effective preventive management strategy nowadays relies on an improved knowledge of the pest biology and ecology and more efficient monitoring and control techniques.
Abstract
This paper presents the first attempt to include soil moisture information from remote sensing in the tools available to desert locust managers. The soil moisture requirements were first assessed with the users. The main objectives of this paper are: i) to describe and validate the algorithms used to produce a soil moisture dataset at 1 km resolution relevant to desert locust management based on DisPATCh methodology applied to SMOS and ii) the development of an innovative approach to derive high-resolution (100 m) soil moisture products from Sentinel-1 in synergy with SMOS data. For the purpose of soil moisture validation, 4 soil moisture stations where installed in desert areas (one in each user country). The soil moisture 1 km product was thoroughly validated and its accuracy is amongst the best available soil moisture products. Current comparison with in-situ soil moisture stations shows good values of correlation (R>0.7R>0.7) and low RMSE (below 0.04 m3 m−3). The low number of acquisitions on wet dates has limited the development of the soil moisture 100 m product over the Users Areas. The Soil Moisture product at 1 km will be integrated into the national and global Desert Locust early warning systems in national locust centres and at DLIS-FAO, respectively.
Keywords
Remote sensing; Soil moisture; Desert locust management; West Africa; SMOS; Disaggregation; Sentinel-1
Understanding Desert Locust population dynamics is a prerequisite for the implementation of a preventive management strategy against its invasions. The present study aims to describe these dynamics through conducting probability analyses of locust presence in time and space. Historical data from field surveys conducted by management teams in Mauritania and Morocco for the period 1988–2015 were used. Temporal smoothing and spatio-temporal extrapolations were performed on a monthly basis. We established monthly probability maps of locust observation following two scenarios: recession period (mainly solitarious phase) and invasion period (mainly gregarious phase). Also, observation probability maps of hoppers or mature adults allowed the identification of seasonal breeding areas. The methodology highlights the potentially favourable areas to be monitored every year. It also highlights the lack of information in some areas of the two countries. We observed that the seasonal survey process during recession periods follow the seasonal pattern of gregarious invasions. We argue that this is the result of climatic conditions related to the oscillation of the intertropical convergence zone. However, we advise that these similar yearly cycles should not hinder surveys in recession periods to be conducted in places not receiving swarms during invasion periods. Nevertheless, we conclude that these maps should be helpful for planning the preparation of survey teams in the field. This will reduce survey operation costs and decrease invasion risks.
Locusts are grasshoppers (Orthoptera: Acrididae) that are characterised by their capacity for extreme population density-dependent polyphenism, transforming between a cryptic solitarious phase that avoids other locusts, and a swarming gregarious phase that aggregates and undergoes collective migration. The two phases differ in any aspects of behaviour, physiology and ecology, making locusts a useful model through which to investigate the phenotypic interface of molecular processes and environmental cues. This review summarises recent progress in understanding the mechanisms and consequences of locust phase change, from differential gene expression and epigenetic regulation through to neuronal plasticity and altered behaviour. The impact of techniques
such as RNA interference and the sequencing of the first locust genome are discussed, and we consider the evidence from comparative analyses between related locust species for the possible evolution of locust-like phenotypic plasticity. Collective movement, and new ways of measuring the behaviour of both migrating bands in the field and individuals in the laboratory, are analysed. We also examine the environmental factors that affect phase change, along with the wider impact of land use and management strategies that may unwittingly create environments conducive to outbreaks. Finally, we consider the human costs of locust swarming behaviour, and use combined social, economic and environmental approaches to suggest potential ways forward for locust
monitoring and management.
The Food and Agriculture Organisation of the United Nations operates a centralised Desert Locust Information Service. Similar to most early warning systems, it relies on accurate information received in a timely manner, in this case, from countries affected by locusts, regional centres and meteorological services. Until recently, this information was managed manually at FAO Headquarters. However, this has changed with the introduction of a computer-based geographic information system. This system operates on a UNIX workstation and uses ARC/INFO and INGRES software. It is connected to a satellite receiving station and to the Internet. The system will allow forecasters to manage locust and environmental data better, and it may encourage more precise data collection in the field. As locust forecasters become more proficient in the use of SWARMS, as field data improve and as remote sensing imagery become validated. FAO should be able to provide more accurate forecasts and early warnings to affected countries FAO should also be able to provide better advice to the international donor community, which in turn could contribute to improved planning and decision making.
Chemical pesticides applied for locust control represent a risk for humans, terrestrial non-target fauna and aquatic ecosystems. This paper reviews the field experience on side-effects. Humans most at risk are field operators themselves. Of the insecticides recommended by the Food and Agriculture Organisation of the United Nations (FAO) specifically, organophosphates and carbamates should be handled with the most care. These compounds also pose a risk to birds, either by direct poisoning or by food depletion. Among the terrestrial non-target invertebrates, there are beneficial species. They appear to be generally affected by treatments, in some cases causing upsurges of secondary pests. Long-term disturbances (over one year) were observed in terrestrial invertebrate communities. The risk of environmental damage can be mitigated considerably by proper selection and use of pesticides. An improvement in the information given decision makers and in the training of operators are essential tools to achieve these goals.
Locusts and grasshoppers continue to pose a threat to agriculture in Africa. To date, insecticides are still perceived as the only effective way of combating locusts. Since 1986, on average 3 million hectares have been treated annually with insecticides in Africa and the Middle East. Since locusts are preferably controlled before they reach cultivated areas, almost any type of ecosystem may be affected by the treatments, including desert grassland, wadis and oases in the Sahara, semi-arid pasture lands in the northern Sahel, and crops further south. Sedentary grasshoppers are mainly sprayed in cultivated areas, but not necessarily while on the crops. Most of the insecticides used are organophosphates (e.g. chlorpyrifos, fenitrothion) or pyrethroids (e.g. deltamethrin, X-cyhalothrin) and have broad-spectrum activity. Recently, more specific chitin synthesis inhibitors (e.g. diflubenzuron, triflumuron) and phenyl pyrazoles (fipronil) are being applied as well.
Cressman, K. and D. Hodson. 2009. Surveillance, Information Sharing and Early Warning Systems for Transboundary Plant Pests Diseases: the FAO Experience. Arab Journal of Plant Protection, 27: 226-232. The Desert Locust (Schistocerca gregaria Forskål) is probably the oldest and most dangerous migratory pest in the world. The UN's Food and Agriculture Organization (FAO) has been operating a surveillance and early warning system for the past 30 years. The system incorporates the collection, transmission and analysis of locust and ecological field data with models, meteorological data and remote sensing imagery to assess current conditions and forecast the scale, timing and location of locust breeding and migration. A variety of information products are disseminated to warn affected countries and donors so that early action can be taken to avoid the development of locust plagues and protect crops and food security. Lessons learned in the Desert Locust system can be applied to other surveillance and monitoring systems. This paper provides an overview of the Desert Locust early warning system and its current application to other transboundary plant pests and diseases, such as wheat rusts.
Desert locust (Schistocerca gregaria, Forskål) plagues have historically had devastating consequences on food security in Africa and Asia. The current strategy to reduce the frequency of plagues and manage desert locust infestations is early warning and preventive control. To achieve this, the Food and Agriculture Organization of the United Nations operates one of the oldest, largest, and best-known migratory pest monitoring systems in the world. Within this system, remote sensing plays an important role in detecting rainfall and green vegetation. Despite recent technological advances in data management and analysis, communications, and remote sensing, monitoring desert locusts and preventing plagues in the years ahead will continue to be a challenge from a geopolitical and financial standpoint for affected countries and the international donor community. We present an overview of the use of remote sensing in desert locust early warning.
The Desert Locust is a major pest in many countries in Africa and the Near East. The episodic invasions are linked to favourable periods of rain in its desert outbreak areas where it originates. Recent studies have dealt with the persistence of the threat and have highlighted the economic, social and environmental issues which are very different from the usual crop protection problems encountered and which require specific actions. Monitoring and control are organised at both the national and regional levels with the support of the FAO (Food and Agriculture organization), thanks to three Desert Locust control commissions. At the international level, the FAO plays a major role - mandated by its members - in the coordination of monitoring and control activities. It operates a central forecasting and warning service and plays an importdnt role in the coordination of assistance, particularly during periods of recrudescence and plague. The Desert Locust Controi Committee was created by FAO in 1955, uniting the concerned countries and is responsible for following the development of locust activity throughout the entire invasion area, defining the most well adapted control strategies, mobilising the resources necessary for control operations, promoting research earmarked for the improvement of locust control and encouraging the coordination of domestic and international operation plans concerned with preventive actions. The last plague, from 1987-1989, the result of the gradual weakening of the preventive control system (responsible for the long recession period beginning in the 1960's) set off the debate once again about the importance of the Desert Locust and control strategies, in which the FAO played a key role. Today's preventive control strategy is still considered as the best possible aproach and consists of two basic elements: early waming and early reaction. In 1994 the FAO launched the EMPRES program, aimed at reinforcing the locust control capabilities of countries with outbreak areas and strengthening related regional and international cooperation. The success of the EMPRES program is vital to ensuring the sustainability of preventive control, to reducing invasion risks, to maintaining food safety in the region and to guaranteeing the preservation of the environment threatened by intensive chemical locust control campaigns.
This paper estimates the long-run impact of a large income shock based on regional variations in the 1987–89 locust plague
in Mali. We take comprehensive population census data to construct birth cohorts of individuals and compare those born and
living in the years and villages affected by locust plagues with other cohorts. We find a clear, strong impact on the educational
outcomes of children living in rural areas, but no impact at all on children living in urban areas. School enrolment by boys
born or less than four at the time of shock is found to be affected. School enrolment by boys born in 1987–88, the main infestation
years, is found to be hardest hit by the plagues. However, although the impact on school enrolment figures is greater for
boys than girls, the educational attainments of girls attending school and living in rural areas are harder hit than the boys.
Our controls for individuals' potentially selective migration behaviour and for differences in school infrastructures do nothing
to change our results. Our findings are also robust to controls for age misreporting and variations in the cohort cut-off
point.
BACKGROUND
Poorly organised risk management system may dysfunction when used. The consequences can be dramatic for those supposed to be protected. Since the 1960s, preventive control strategies, which field officers are the living memory, have been developed to monitor locusts. Preserving their experience of past plagues is consequently essential. Wrong use of their knowledge can disrupt the whole management chain. We explored these conditions using a multi-agent model representing a preventive system. We simulated how the field teams’ tendency to repeatedly visit past outbreak areas (hotspots) by allocating them an attraction weight, can help in preventing plagues.
RESULTS
When field teams’ attention remained constant over time, there was dramatic decrease in the number of plagues with increasing interest in hotspots, as long as interest was less than 2.5 times more than elsewhere. When the field teams were only attentive during recession times, plagues were better controlled using a low weight for hotspots. The spatial structure of hotspot distribution had an effect: the more frequent and the bigger the hotspots, the lower the optimal hotspot weighting needed to reduce plagues.
CONCLUSION
Orienting surveys towards hotspots particularly during recession times reduces plagues. The spatial structure of locust habitats may influence the way to manage them. Habitats located outside the multiple hotspots of species such as the desert locust should be visited more frequently than those with only one hotspot, such as the South American locust. The decline/loss of the field officers’ experience highlights the need to save, capitalize and disseminate this knowledge.
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The desert locust (Schitocerca gregaria) swarms in numbers that decimate farmland, threatening an already vulnerable horn and Eastern region of Africa. The aim of this research was to assess the nutrient content and oil characteristics of the desert locust and for possible utilization as a food resource at industrial scale. The desert locusts were harvested from swarms in various regions of Kenya. Nutrient analysis was performed using standard protocols and physico-chemical characteristics of the extracted oil were evaluated. A 100 g sample contained 450Kcal energy, 46 g protein, 32 g fat and 4 g fibre. Calcium was the most abundant macro mineral (208.36 mg/100 g), iron was the most abundant trace mineral (4.83 mg/100 g) while α-tocopherol content of 267.47 µg/g was recorded. Oleic acid was the main fatty acid (30.78%) with total unsaturated fatty acids being 66.47% of the total fatty acids. The n-6:n-3 ratio of 2,4 was reported which indicated a significant nutritional quality of the locust oil. The locust oil had 0.94 specific gravity indicating potential industrial applications. Iodine value (75 g iodine/100 g oil), peroxide value (0.18 mEq/Kg) and saponification value (171 mg KOH/Kg) indicated an oil with relative stability and potential for industrial utilization in the food industry. As a result, locust control efforts could therefore include harvesting and consumption as part of the integrated management.
The current outbreak of the Desert Locust has affected much of eastern Africa and has reached as far as Pakistan and India in Asia, generating significant agricultural losses in a region that is already highly unstable economically, politically, and in terms of food security for its human populations. During the last 50 years the management strategy for this pest resulted in a considerable decrease in the number and intensity of outbreaks and plagues. Socio-political instability in some key areas for this locust is mainly responsible of the current situation. Climatic events observed since 2018 fall within the historical range, even if an impact of global changes in the future is foreseeable. The highest priorities should be (a) to ensure that the political and socio-economic conditions are in place so that vulnerable human populations can adapt to new large-scale threats and (b) to maintain a culture of long-term risk assessment with constant necessary means.
Background:
The spatial structure of locust outbreaks is a major aspect of preventive management that relies on where survey teams have to be sent in order to react in time to any upsurge. The concentration of areas propitious to outbreaks has been documented for many species. Areas where preventive management fails to collect information because of insecurity or remoteness constitute other limits. We explored these conditions with a spatially-explicit multi-agent model representing a preventive management system. We simulated areas where field teams had limited or no access and areas where the probability of initial outbreaks was concentrated in hotspots.
Results:
A strong effort of the budget holder to maintain funding over time might be cancelled out with 5% of a territory having limited access. The larger the no access areas were, the worse was the proportion of plague years. Several no access areas generated more plagues than only one no access area of equivalent size because more fronts must be controlled. Concentrating outbreaks in hotspots increased the probability of plagues. Only one hotspot was easier to control than several same-sized hotspots. The period of the budget holder's cyclical behaviour between awareness and reduction in funding was longer with one hotspot than with several.
Conclusion:
These results highlight the need to consider the spatial condition and accessibility of locust species when planning the sustainability of management systems. Despite the significant budgets to set in place a preventive management system, cyclical locust outbreaks may be related to these spatial conditions. This article is protected by copyright. All rights reserved.
Acridids (grasshoppers and locusts) can range from being rare curiosities to abundant menaces. Some are threatened with extinction and become subjects of intensive conservation efforts, while others are devastating pests and become the objects of massive control programmes. Even within a species, there are times when the animal is so abundant that its crushed masses cause the wheels of trains to skid (the Rocky Mountain grasshopper, Melanoplus spretus Walsh in western North America in the 1860s and I 870s), while at other times the animal is alarmingly scarce (the Rocky Mountain grasshopper went extinct in the early 1900s). Why are there these extremes in one insect family, and even in a single species? The NATO workshop examined this paradox and its implications for Environmental Security, which must address both the elements of land use (agricultural production and pest management) and conservation of biodiversity. The reconciliation of these objectives clearly demands a critical assessment of current knowledge and policies, identification of future research, and close working relationships among scientists. Insects can present two clear faces, as well as the intervening gradation. These extremes require us to respond in two ways: conservation of scarce species and suppression of abundant (harmful) species. But perhaps most important, these opposite poles also provide the opportunity for an exchange of information and insight.
Preventive management of locust plagues works in some cases but still fails frequently. The role of funding institution awareness was suggested as a potential facilitating factor for cyclic locust plagues. We designed a multi-agent system to represent the events of locust plague development and a management system with three levels: funding institution, national control unit and field teams. A sensitivity analysis identified the limits and improvements of the management system.
The model generated cyclic locust plagues through a decrease in funding institution awareness. The funding institution could improve its impact by increasing its support by just a few percent. The control unit should avoid hiring too many field teams when plagues bring in money, in order to assure that surveys can be maintained in times of recession. The more information the teams can acquire about the natural system, the more efficient they will be.
We argue that anti-locust management should be considered as a complex adaptive system. This would not only allow managers to prove to funders the random aspect of their needs, it would also enable funders and decision-makers to understand and integrate their own decisions into the locust dynamics that still regularly affect human populations.
The desert locust is an agricultural pest that is able to switch from a harmless solitarious stage during recession periods, to swarms of gregarious individuals that disperse long distances and affect areas from western Africa to India during outbreak periods. Large outbreaks have been recorded through centuries, and the Food and Agriculture Organization keeps a long-term, large-scale monitoring survey database in the area. However, there is also a much less known subspecies that occupies a limited area in southern Africa. We used large-scale climatic and occurrence data of the solitarious phase of each subspecies during recession periods to understand whether both subspecies climatic niches differ from each other, what is the current potential geographical distribution of each subspecies, and how climate change is likely to shift their potential distribution with respect to current conditions. We evaluated whether subspecies are significantly specialized along available climate gradients by using null models of background climatic differences within and between southern and northern ranges, and applying niche similarity and niche equivalency tests. The results point to climatic niche conservatism between the two clades. We complemented this analysis with species distribution modeling to characterize current solitarious distributions and forecast potential recession range shifts under two extreme climate change scenarios at the 2050 and 2090 time horizon. Projections suggest that, at a global scale, the northern clade could contract its solitarious recession range, while the southern clade is likely to expand its recession range. However, local expansions were also predicted in the northern clade, in particular in southern and northern margins of the current geographical distribution. In conclusion, monitoring and management practices should remain in place in northern Africa, and in southern Africa the potential for the subspecies to pose a threat in the future should be investigated more closely. This article is protected by copyright. All rights reserved.
This study addresses geographic variation of body size and shape and of allele frequencies at 21 microsatellite loci in southern African populations of the desert locust, Schistocerca gregaria. These populations, which belong to the subspecies S. g. flaviventris, lack the capacity to change phase and to swarm relative to the northern populations of the nominate subspecies, S. g. gregaria. We reported overall genetic and morphological similarities among localities that cover most of the subspecies range. Of particular interest, the level of genetic diversity was moderately lower than in the swarming subspecies of the northern range. In addition, S. g. flaviventris populations were genetically homogeneous, such as observed in the northern range of the nominate subspecies. This result can be explained by north-southwest seasonal migration to follow rainfall.
The desert locust, Schistocerca gregaria (Forskal) (Orthoptera: Acrididae), is a major pest and well known in its gregarious phase. However, it is not well understood during recession periods, when the solitarious phase populations are discrete. Nonetheless, these populations are at the origin of the invasions when ecological conditions become favourable. This lack of knowledge of the solitarious phase individuals impedes effective preventive management of this pest. Archive data collected in Algeria from 1980 to 2011 were used to analyse solitarious population dynamics across the Algerian Sahara where some outbreak areas are located that play a major role in the invasion process. The results confirm previous empirical observations on solitarious population dynamics. First, a clear difference could be documented between the northern and southern Saharan regions of Algeria concerning the locust dynamics and the impact of environmental conditions. The importance of runoff was clear to create suitable habitats over a long period and to very distant places from rainy areas. Second, a link, on an annual basis, between green vegetation and presence of solitarious locusts was found. Third, statistical relationships between various locations demonstrated a clear regional dynamics. Our study confirmed the importance of migrations of solitarious populations among Algerian regions and more generally within the recession area of this species. The operational implications of these findings are multiple. First, they confirm the need of a flexible and scalable preventive system during the year, from 1 year to another and with a clear distinction between the northern and southern Saharan areas of Algeria. Second, they also confirm the necessity for the inclusion of wadis and soil moisture estimations from remote sensing in geographic information systems for preventive management. And third, they clearly illustrate the importance to target solitarious locusts for more efficient preventive survey operations.
We evaluated the validity of the subspecific designation for Schistocerca gregaria gregaria (Forskål) and Schistocerca gregaria flaviventris (Burmeister), isolated in distinct regions along the north–south axis of Africa. Towards this goal, we assessed the variation of multiple morphological and molecular traits within species. We first used elliptic Fourier and landmark-based relative warps analyses to compare the size and shape of two internal and two external structures of male genitalia. We provide a discriminant function which classified the specimens with 100% accuracy and selected shape elements of the external structures only (cercus and epiproct). We also tested eight molecular markers, and because of either absence of variation or contamination by mitochondrial DNA (mtDNA)-like sequences, we used a clone-and-sequence analysis of the standard cytochrome c oxidase subunit I mitochondrial DNA barcode only. We differentiated 185 true mitochondrial sequences from 66 mitochondrial DNA-like sequences, most of which were from S. g. gregaria specimens. On the dataset of mitochondrial origin, we identified three characteristic point mutations that diagnosed the two allopatric subspecies with 94% accuracy. Minimum spanning network and parsimony tree analyses identified S. g. flaviventris as a monophyletic lineage distinct from the nominate subspecies. Accordingly, microsatellite data indicate rarely occurring admixture events only, showing that independent evolutionary history is the norm.
For desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), the hopper density threshold of gregarization remains poorly documented. Field sampling was carried out in traditional seasonal breeding areas of Mauritania during two successive years without invasion to approximate the gregarization threshold. Hopper densities were assessed at numerous sampling sites. Vegetation was also sampled to characterize the habitats. Hopper behavior was analyzed in situ with the help of a behavioral circular arena to test our assumptions on empirical locust phases determination based on physical appearance (coloration and behavior) following FAO guidelines. The results provided a critical density value around 2.45 hoppers m−2, above which gregarious hoppers were expected to be seen more frequently in nature. Hopper density was confirmed as the main factor explaining the presence of gregarious individuals. The level of involvement of vegetation parameters such as plant density, basal area, volume, distance between plants, greenness, or combinations of these indicators was low in explaining the observation of gregarious hoppers compared with hopper density. Vegetation cover and height were the only vegetation characteristics that could enhance the prediction of phase status with hopper density. The hoppers' phase determined from their behavior observed in the arena was similar to that characterized through FAO guidelines phase assessment, making consistent the field sampling method. Additionnally, the use of this arena illustrated that the grouping behavior of hoppers is a gradual response to density. This study can be seen as a step forward in the estimation of hopper density thresholds of gregarization in the field. This should improve the decision making for intervention during preventive control operations.
Variations in the incidence of plagues of 4 locust species were independent of any differences in the intrinsic rate of natural increase (r) for each species. Behavioural changes in locusts, as density increases, prevent populations exceeding carrying capacity of the habitat, and it is unlikely therefore that intrinsic population fluctuations, predicted by the logistic model, contribute to the periodicity of plagues. Small variations in immature survival, rather than natality, account for most of the differences in the growth rates of field populations and are largely controlled by the direct and indirect effects of rainfall. In 3 of the species, high rates of population growth occur under favourable environmental conditions and are capable of initiating outbreaks in the course of only 2 or 3 generations. Outbreaks are also influenced by the increases in population density associated with concentration. Stochastic interactions between meteorological factors and locust populations in the recession and invasion areas, control the plague dynamics of the species studied. -from Authors
Little quantitative information is available on the natural mortality of the desert locust and it all comes from eastern Africa. The problems of such studies arise from the extreme mobility of the desert locust, its wide range of habitats and its changes of phase. The different types of natural enemies affecting the desert locust are listed. The losses of eggs and of post-embryonic stages are discussed separately; techniques of study as well as results are noted. The eggs of solitary and gregarious desert locusts must be investigated in different ways. Entomophagous insects, particularly Stomorhina lunata (Calliphoridae), Systoechus spp. (Bombyliidae) and Trox procerus (Trogidae), are important causes of mortality of phase gregaria but do little damage to phase solitaria. The post-embryonic stages are eaten by birds which can be a major factor in the extinction of a small population. Other predators are too little known for an assessment of their role to be made. Insect parasites, especially Blaesoxipha spp., may play an important part in controlling small non-gregarious populations. Large gregarious populations are less affected, though Symmictus costatus (Nemestrinidae) can parasitize a large proportion. Mortality due to inability to moult and to cannibalism is widespread and possibly universal. Heavy mortality of first and second instar nymphs which is possibly a mechanism for the elimination of unsuitable genotypes is also discussed. Dempster's (1963) conclusion that weather is the ultimate controlling factor of acridid populations is criticized because biotic factors may be more important in tropical areas than he believes. An attempt is made to estimate the range of multiplication rates encountered. It seems that rates of over 11 for gregaria or 16·5 for solitaria are unlikely. If this is true it is shown that quite acceptable rates of parasitism and predation are capable of preventing increases in locust populations. Much more detailed quantitative work is needed.
In the desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), the threshold density inducing the gregarization phenomenon has never been determined under natural conditions. The influence of environmental factors on this phenomenon has been studied mostly in controlled environments. Based on data collected during several years by the survey teams of the National Center for Locust Control in Mauritania, we analyzed the influence of locust density, vegetation cover, and vegetation status on the probability of observing gregarious locusts. We assumed that a probability to observe gregarious locusts of 0.5 corresponded to the density threshold of gregarization. The results showed in detail the change in the threshold of gregarization according to the cover and status of the vegetation. Low cover and dry vegetation led to a low density threshold of gregarization probably due to high probability of individuals to touch each other. Dense and green vegetation favored a high threshold of gregarization probably due to a dispersion of the individuals and a low probability of individual encounters. These findings should help the management of locusts and decision making during control operations.