From Surveillance to Sustainable Control: A Global Review of Strategies for Locust Management

Abstract

Locusts represent a persistent global agricultural pest, responsible for significant crop losses and socio-economic repercussions. The initiation of chemical control measures dates back to the late 19th century, with the use of poisoned baits, before advancing in the mid-20th century with the introduction of organochlorines, such as dieldrin. Despite their efficacy, the associated environmental, ecological, and human health risks led to the prohibition of dieldrin by the United States and the FAO by 1988. The demand for insecticides with reduced persistence and toxicity prompted the establishment of international organizations to coordinate locust research and management. In recent decades, chemical control has transitioned towards compounds with diminished persistence and selective agents. Concurrently, research has progressed in the development of bioinsecticides, notably Metarhizium acridum, and has reinforced preventive strategies. Emerging technologies, including remote sensing and machine learning, have facilitated early monitoring and predictive modeling, thereby enhancing outbreak forecasting. These tools support proactive, targeted interventions and are consistent with Integrated Pest Management principles, promoting more sustainable and ecologically responsible locust control strategies.

1. Introduction

Locusts represent a specific subset of grasshoppers within the Acrididae family [1,2,3], distinguished by their ability to undergo density-dependent phase polyphenism, a phenomenon initially described by Uvarov (1921) [4,5,6]. Under favorable environmental conditions [1,2], locusts transition from a solitary phase to a gregarious one, forming highly mobile hopper bands and swarms capable of consuming their body weight in vegetation daily and traveling hundreds of kilometers [1,2,7,8]. Unlike most orthopterans, these species exhibit polyphagous feeding behavior during outbreaks, targeting a wide array of crops and wild plants [2,3,8,9], thereby ranking among the most destructive insect pests globally [1,10,11]. Of the approximately twelve recognized locust species, the migratory locust (Locusta migratoria), desert locust (Schistocerca gregaria), Moroccan locust (Dociostaurus maroccanus), and Italian locust (Calliptamus italicus) are the most economically significant [1,8,10,11]. These species thrive in arid and semi-arid environments where alternating droughts and rainfall promote breeding and gregarization [1,2,8,11]. Historical records of locust plagues span Europe, Africa, and Asia, leading to recurrent food insecurity and socioeconomic disruption [1,2,3,12]. In the past two decades, significant events such as the 2003–2005 West African desert locust plague, which impacted over 8 million people [1,8,13] and incurred costs exceeding $400 million in control operations [14], and the 2019–2021 East African upsurge, one of the most severe in recent history, have underscored the persistent global threat posed by these insects [3,12].

Over the past century, strategies for managing locust populations have evolved significantly, transitioning from initial mechanical methods to the extensive use of chemical spraying in the mid-20th century [1]. Although chemical insecticides continue to be the primary method of control [1,2,11], they are predominantly reactive and present substantial risks to human health, biodiversity, and ecosystems [1,2,3,15]. These limitations have prompted a gradual shift towards integrated pest management, incorporating the operational use of biocontrol agents such as Metarhizium acridum, as well as the implementation of new technologies such as remote sensing technology, unmanned aerial vehicles (UAVs), and machine learning to improve forecasting and early warning systems [2,11,16].

Despite these advancements, most control campaigns remain reactive [1,2], initiated only when swarms pose a direct threat to crops [17,18,19]. Preventive control, as originally conceptualized by Boris Uvarov, is often misconstrued as synonymous with “outbreak prevention” [20,21,22,23]. In practice, preventive control involves early interventions in outbreak areas to safeguard major agricultural zones, whereas complete outbreak prevention is seldom feasible [5,11,22,24,25]. This misunderstanding, along with financial, logistical, and political constraints, has hindered the consistent adoption of preventive strategies [5,6,19,26,27].

This review critically examines the evolution of locust management, from historical mechanical and chemical approaches to contemporary biological and technological innovations. By integrating historical and recent evidence, we highlight both key advances and persistent challenges, particularly the difficulty of transitioning from reactive crisis responses to sustainable preventive control. We argue that effective locust management in the 21st century must integrate biocontrol, climate- and AI-informed forecasting, and strong institutional cooperation into a coherent preventive framework that safeguards food security in vulnerable regions.

2. Literature Search and Selection Strategy

This article is organized as a narrative review that integrates research on locust management strategies, with a specific emphasis on methodologies endorsed or assessed by the Locust Pesticide Referee Group (LPRG) of the Food and Agriculture Organization (FAO). Although it does not adhere to a strict systematic review protocol, efforts were undertaken to ensure transparency and comprehensiveness in identifying pertinent studies.

Search Databases and Keywords

Between 10 February and 12 September 2025, a comprehensive literature search was systematically conducted across prominent scientific databases, including Google Scholar, ResearchGate, ScienceDirect, Scopus, and Web of Science. The search strategy employed a combination of keywords such as:

“locust control*”;

“integrated locust management”;

“biological control of locusts”;

“chemical control of locusts”;

“locust monitoring”;

“outbreak prevention”;

“remote sensing”.

We also used species-specific terms, such as Locusta migratoria, Schistocerca gregaria, and Dociostaurus maroccanus.

Inclusion and Exclusion Criteria

Eligible sources comprised peer-reviewed articles, review papers, technical reports, and guidelines from international organizations such as the FAO, EFSA, and EPA. Excluded from consideration were studies not available in English, conference abstracts lacking full texts, and publications that did not directly pertain to locust management. An initial pool of 112 records underwent title and abstract screening, followed by a full-text evaluation, resulting in a final selection of sources that informed this review.

Data Extraction and Synthesis

Data were synthesized narratively rather than quantitatively, emphasizing

• The historical evolution of control strategies;
• The efficacy and ecological impacts of chemical, biological, and preventive methods;
• The role of emerging technologies such as biocontrol, remote sensing technology, UAVs, and AI-driven forecasting.

3. The Institutionalization of Locust Control: Historical Milestones and Global Cooperation

Locusts have been acknowledged as significant agricultural pests since ancient times [1,10,11]; however, international initiatives to formalize their control commenced only in the early 20th century. In 1905, Jules Künckel d’Herculais orchestrated one of the initial international campaigns in Algeria [4,6,26], culminating in the 1916 global locust report by the International Institute of Agriculture, which underscored the pressing necessity for cross-border collaboration [4]. The inaugural international conference on locust control, convened in Rome in 1920, formally signified the commencement of institutionalized management [4,26,28].

During this period, pivotal scientific advancements were achieved. In 1921, Boris Uvarov identified phase polyphenism [4,5,6], a groundbreaking discovery that revolutionized locust research and continues to underpin management strategies [29]. By the 1930s, cooperation expanded through a series of international conferences (Rome 1931, Paris 1932, London 1934, Cairo 1936, Brussels 1938), which highlighted the necessity for global action [4,6,17,24].

Institutional frameworks soon emerged. France established the Comité d’Etudes de la Biologie des Acridiens in Algeria (1932) [4,6], which evolved into the ONAA (1943) [6,30], while Britain founded the Anti-Locust Research Centre (ALRC) in 1945 [6,24,31], later reorganized into several development institutes before becoming today’s Natural Resources Institute [6]. The establishment of the FAO in 1945 was a pivotal moment, providing a permanent platform for global coordination [6,26]. Major initiatives included the Desert Locust Control Committee (DLCC, 1954), the Desert Locust Information Service (DLIS, 1978) [5,6], and the Emergency Prevention System (EMPRES, 1994), which emphasized early warning and preventive action across Africa and the Near East [6,28,32,33].

More recently, regional commissions such as CLCPRO (2000) have reinforced collaboration among frontline states [26,28]. Today, FAO-led systems integrate satellite imaging, AI-driven models, drones, and GIS platforms for real-time monitoring and forecasting. These advancements represent the culmination of a century-long institutional trajectory [5,6,13,26,28].

Despite these accomplishments, international coordination remains limited [6]. Control programs in numerous affected countries are hindered by inadequate funding, fragile governance, and insufficient preparedness, which delay responses [6,11,17,34]. Donor funding remains cyclical—peaking during plagues but diminishing during economic downturns—thereby undermining the long-term preventive ethos originally envisioned by Uvarov [6,10,17].

Furthermore, the uneven adoption of modern technologies such as satellite-based early warning systems, UAVs, and predictive modeling highlights capacity disparities between well-resourced and resource-poor countries. Political instability and bureaucratic inertia further impede effective cross-border coordination [6,17].

Critically, while the institutional framework for locust control has become increasingly sophisticated, its effectiveness still relies more on sustained political will and financing than on technical capacity. Without addressing these structural bottlenecks, global locust control remains susceptible to the same reactive cycles documented for over a century.

4. Locust Control Approaches

The management of locust populations has traditionally been categorized into two primary strategies: the reactive approach and the preventive approach [18,23]. Although recent literature has introduced the term “proactive” as an intermediate concept, this has frequently led to confusion [21,23,35]. Consistent with Uvarov’s original framework and the prevailing consensus among locust specialists [5,22,24,25], we identify only two principal approaches—reactive and preventive—while elucidating the limitations of “outbreak prevention” as a distinct concept [21,22,23].

4.1. Reactive Approach

The reactive approach pertains to interventions initiated only after swarming has occurred and substantial populations are already in motion. This approach characterized much of the 20th century and continues to be the standard response during emergency plague situations [17,18,19,23]. Typically, reactive operations involve large-scale aerial or ground spraying of broad-spectrum insecticides over extensive infested areas [1,2,11], necessitating considerable financial resources and logistical coordination [5,10,27,36,37]. The efficacy of such operations in mitigating immediate crop damage has been consistently demonstrated; however, they are accompanied by several significant drawbacks: high operational costs [1,2,14], reliance on international donor funding [6,10,17,34,36], risks to human health and non-target biodiversity, and the challenge of containing highly mobile swarms that may traverse political borders within days [1,2,3,15]. Consequently, reactive campaigns are frequently criticized as being untimely, costly, and environmentally unsustainable, although they remain indispensable when early control efforts fail or are not implemented in a timely manner [2,14,16].

4.2. Preventive Approach

Preventive control, as initially conceptualized by Uvarov in the early 20th century, represents a strategic shift from reactive crisis management to proactive early intervention [5,22,23,37]. The core principle of this approach is the timely identification and management of nascent outbreaks in established breeding areas to prevent their escalation into widespread plagues [5,22,24,25]. It is crucial to distinguish preventive control from the absolute prevention of outbreaks, as outbreaks are an inherent aspect of locust ecology and cannot be entirely averted in practice [5,20,21,23]. Instead, as emphasized by Uvarov, the objective is to manage outbreaks and safeguard key agricultural regions through ongoing monitoring, forecasting, and swift localized interventions [5,22,23,37].

The practical application of preventive control is founded on three main components: (1) early warning systems that integrate field surveys with meteorological and remote-sensing data to detect breeding conditions [6,38,39,40,41]; (2) institutionalized monitoring and coordination, often facilitated by the FAO or regional organizations [4,5,6,17,27,31]; and (3) targeted interventions, typically employing insect growth regulators or biological agents, applied in barrier treatments rather than extensive blanket spraying [1,5,6,11,39,40,42,43]. This model has been progressively institutionalized since the mid-20th century and is regarded by many experts as the “best practice” in locust management [11].

The efficacy of preventive control has varied considerably across different locust species and regions. For species with relatively confined outbreak areas, such as the red locust (Nomadacris septemfasciata) in southern Africa, the African migratory locust (Locusta migratoria migratorioides) in the Sahel, and the South American locust (Schistocerca cancellata), preventive measures have often been successful in preventing plagues for extended durations, sometimes spanning decades. In these instances, the ability to focus surveillance and interventions within limited outbreak zones significantly enhances the likelihood of success [10,36,37].

In contrast, for more widespread and highly mobile species such as the desert locust (Schistocerca gregaria) and the Australian plague locust (Chortoicetes terminifera), preventive control measures can only partially mitigate outcomes. Although preventive programs have succeeded in reducing the size, duration, and frequency of plagues in these species, complete prevention remains elusive. Environmental variability, extensive breeding ranges, and the rapid mobility of swarms often exceed the capabilities of even well-funded surveillance systems [10,36,37].

Thus, distinguishing between preventive control and outbreak prevention is crucial. While outbreak prevention has occasionally been proposed as the ultimate objective, it has proven unattainable in practice, particularly for species with continental distributions. Misunderstandings of these terms have led to debates regarding program effectiveness and resource allocation [5,20,21,22,23]. As Hunter, 2024 emphasizes, the true measure of success lies not in preventing outbreaks entirely, but in mitigating their impact and protecting major agricultural areas through accurate forecasting and timely, targeted interventions [11].

Over recent decades, preventive control has largely met this benchmark in numerous regions. Uvarov’s original vision—safeguarding key agricultural zones from devastating plagues—has been realized through the establishment of early warning systems, regionally coordinated monitoring, and increasingly sustainable intervention strategies [3,5,13,23,40]. Nonetheless, challenges persist, particularly the reliance on organophosphate insecticides, the underutilization of biological agents [23,25,26,41,44], and the susceptibility of preventive programs to funding shortages and political instability [6,17,37].

The dual framework of reactive versus preventive control remains the most effective conceptual model for locust management [37]. While reactive measures will continue to be necessary during crisis situations [1,2,17,18,19,23,37], preventive control represents the most sustainable approach, contingent upon adequate resourcing, scientific support, and institutional integration [6,17,18,19,23,36,37]. Although outbreak prevention may be an aspirational goal, in practice, the true measure of success lies in impact mitigation and the protection of agriculture, rather than the ecological suppression of the outbreaks themselves [5,20,21,22,23].

5. Preventive Methods

The foundation of modern preventive locust control strategies can be traced back to 1921, when Uvarov introduced the phase polyphenism theory to elucidate the recession and upsurge of locust populations [22,23,45]. This theory significantly enhanced the understanding of locust biology and laid the groundwork for the development of effective preventive measures [5,22,23]. Over a decade later, Uvarov proposed the original plague prevention strategy to avert crop damage in the principal agricultural regions of Africa, the Near East, Iran, and Indo-Pakistan [5,22,24,25]. According to this original preventive strategy, crop damage could be mitigated by managing hopper bands and swarms in outbreak areas [5,22,24,25]. Thus, preventive control and outbreak prevention should not be conflated [22]. On one hand, preventive control methods aim to reduce crop damage, as Uvarov proposed [20,22,24]. On the other hand, outbreak prevention endeavors to maintain locust population densities at a minimal level indefinitely [21,22,23].

Historically, preventive campaigns relied on long-residual insecticides such as dieldrin, which remained active in the soil for months and effectively suppressed hopper development. However, increasing awareness of their environmental persistence and ecological impacts led to their prohibition [5,46]. This shift created a critical gap: while the principle of preventive control remains valid, its implementation has become increasingly challenging without comparable alternatives [5].

Contemporary preventive strategies prioritize early detection, targeted biocontrol, and environmentally sustainable interventions. Technological advancements in satellite imaging, remote sensing, unmanned aerial vehicles (UAVs), and machine-learning models have significantly enhanced the precision in identifying potential outbreak zones [3,5,13,23,47]. Biopesticides, such as Metarhizium acridum, offer operationally viable and safer alternatives [48,49,50,51]; however, their limited persistence, elevated costs, and logistical challenges, including cold-chain storage and slower kill rates, constrain their scalability in preventive programs [26,41,51,52].

Despite its recognition as the most sustainable approach to locust management, preventive control remains the least consistently implemented strategy. The primary obstacles are not rooted in scientific knowledge but rather in structural and operational limitations [5,19,26]. Financial instability, characterized by donor-driven funding cycles that dissipate between plagues, undermines long-term preparedness [6,17,34]. Logistical constraints, such as the necessity for year-round surveillance, rapid deployment capacity, and cold-chain infrastructure for biopesticides, render implementation particularly challenging in resource-limited regions [6,11,17]. Technical bottlenecks also persist: although biopesticides and precision-monitoring tools are available, their adoption in the field is impeded by formulation, storage, and cost barriers [6,41,44]. Furthermore, political and institutional fragility, especially in frontline countries, restricts cross-border cooperation and delays coordinated action [6,17,37]. Consequently, preventive control remains more of an aspirational framework than an operational reality, with most countries continuing to rely on proactive or reactive strategies. Bridging this gap necessitates sustained financing, international commitment, and the translation of technological advances into field-ready solutions [5,27,37].

6. Mechanical Control Methods

Mechanical control constitutes the earliest method of locust management, preceding the advent of chemical and biological strategies [25]. Historically, communities employed direct physical interventions to mitigate damage from hopper bands and swarms [25]. Common techniques included excavating trenches to trap and bury hoppers, incinerating infested vegetation [25,33,51,53,54], and utilizing manual tools to crush or disorient locusts [24,25,33]. In certain regions, specialized collection machinery was introduced [25,54], while other practices involved the use of fire, smoke, or loud noise to repel swarms [24,35,53,54,55].

Paraffin-based sprays were occasionally applied to impair locust mobility and reproduction [54], while the destruction of egg pods through plowing or digging was employed as a preventive measure [24], albeit often with limited success [24,25]. Other localized measures included protective nets treated with natural repellents, such as garlic or neem oil, to safeguard nurseries and small agricultural plots [33,53,56].

Although mechanical methods were indispensable prior to the pesticide era, they are labor-intensive, locally constrained, and unsuitable for large-scale infestations [9,57]. Their historical significance lies in providing immediate protection to farmers and laying the groundwork for subsequent, more advanced control practices. Presently, they retain value primarily for smallholder farmers and localized outbreaks, particularly in contexts where chemical or biological options are unavailable or unaffordable. However, their scalability and sustainability are severely limited, precluding them from substituting modern integrated approaches. Instead, their relevance is best understood as complementary measures within broader Integrated Pest Management (IPM) strategies, where community-based action can reinforce more systematic interventions [1,2,25,33,37].

7. Chemical Control

Since the mid-20th century, chemical insecticides have constituted the primary strategy for locust management, facilitating rapid and extensive suppression of outbreaks [25,26,44]. Initial approaches utilized poisoned baits containing arsenic or organochlorines; however, these methods were found to be either inefficient or environmentally persistent [24,51,54,58]. The introduction of dieldrin in the 1950s marked a significant advancement in locust control due to its prolonged residual activity, which enabled effective “barrier spraying” against hopper bands [25,31,54]. Nevertheless, its persistence, bioaccumulation, and toxicity to wildlife [54,59] resulted in international prohibitions by the 1980s [40].

In response, the Food and Agriculture Organization (FAO) established the Locust Pesticide Referee Group (LPRG) in 1989 [41,47] to assess insecticides for efficacy, safety, and environmental impact [41,47]. This group formulated standardized guidelines, emphasizing barrier treatments over blanket applications and advocating for the adoption of less toxic alternatives, such as insect growth regulators (IGRs) and biological pesticides [32,43,46,48,49,50,60,61,62,63]. Despite these initiatives, the majority of operational campaigns continue to rely on neurotoxic insecticides, including organophosphates and pyrethroids, primarily due to their availability and cost-effectiveness [43].

Main Pesticide Groups

Organochlorines, including compounds such as DDT, dieldrin, aldrin, and BHC, were the initial synthetic insecticides extensively employed in locust control from the late 1940s onwards [25,54]. Their prolonged persistence and stomach-poison action facilitated barrier treatments and large-scale aerial spraying, thereby revolutionizing control campaigns [25,31,51,53,54,64]. However, due to their bioaccumulation, ecological toxicity, and associations with human health risks [41,65], widespread bans were initiated in the 1970s [25,54], with the FAO officially prohibiting the use of dieldrin in 1988 [40].

The Locust Pesticide Referee Group (PRG), established by the FAO in 1989 [41,47] and renamed LPRG in 2021 [41], systematically reviewed insecticides for efficacy and environmental safety [41,47]. Over time, it approved organophosphates, pyrethroids, carbamates, insect growth regulators, fipronil, and the biopesticide Metarhizium acridum, gradually guiding locust management towards safer compounds. Despite this progress, campaigns continue to rely heavily on organophosphates and pyrethroids due to their cost-effectiveness, and few new products have been introduced in recent decades [32,43,46,48,49,50,60,61,62,63].

Organophosphates (OPs), such as fenitrothion, malathion, and chlorpyrifos, emerged as the primary substitutes for organochlorines [25,61] and remain the cornerstone of modern locust control [43]. These compounds function as fast-acting cholinesterase inhibitors, providing high efficacy in both hopper and adult stages [41]. They are widely available and relatively inexpensive, making them particularly valuable for large-scale emergency campaigns [43]. However, they also pose acute toxicity risks to applicators, pollinators, and aquatic organisms, and chronic exposure has been linked to human health effects [41,48,66,67,68]. Increasing regulatory restrictions and public concern underscore the urgent need for safer alternatives in future control programs [41,69,70].

Pyrethroids, including synthetic variants such as deltamethrin and lambda-cyhalothrin, are preferred for emergency spraying due to their rapid knockdown effect on locust populations [62,71]. These compounds are frequently applied in ultra-low-volume (ULV) formulations, which allow for effective coverage with minimal quantities of active ingredient [25,26]. Despite their operational appeal, the high toxicity of pyrethroids to non-target insects, particularly bees and other pollinators, as well as their detrimental effects on aquatic organisms, poses significant challenges to their long-term sustainability [49,50,71]. Additionally, sublethal effects on insect physiology and the development of resistance in certain pest species further exacerbate these concerns [72]. Nonetheless, pyrethroids remain among the most commonly utilized compounds in reactive locust control efforts globally [41,71].

Insect Growth Regulators (IGRs), specifically benzoylurea-based IGRs, have been endorsed over the years for locust control strategies by the LPRG [62]. The insecticidal action of IGRs is predicated on the inhibition of chitin synthesis [41,64], rendering them effective solely for hopper control, as adult locusts are not significantly impacted [51,62]. Due to their prolonged foliar persistence, IGRs have been deemed suitable for barrier spray treatments since 1994 [23,62,73]. However, their slow mode of action renders them inadequate for emergency responses during large swarms [63], and regulatory prohibitions in the European Union have further restricted their availability [41,74]. Despite these limitations, IGRs continue to play a crucial role in preventive control, particularly when employed in targeted barrier treatments during the early stages of outbreaks [41].

Phenylpyrazoles: Fipronil, a phenylpyrazole insecticide, has demonstrated remarkable efficacy against locusts at minimal dosages, rendering it a promising candidate for barrier treatments [32,47,63,75]. However, research has underscored its significant toxicity to aquatic arthropods, soil invertebrates, and other non-target organisms, thereby raising substantial ecological concerns [47,48,49,50]. Consequently, its operational application has been confined to limited use in non-crop areas [43,47,49,50]. Although fipronil remains on the FAO’s list of recommended insecticides for locust control, its role has been considerably diminished as international agencies increasingly prioritize environmental safety and sustainability. Its future utilization is likely to decline further unless new, safer formulations become available [41,74].

Neonicotinoids: Compounds such as imidacloprid and thiamethoxam were evaluated for locust management during the late 1990s and early 2000s [48], initially showing promise due to their systemic action and relatively novel mode of activity [49,76]. However, evidence from both field and ecotoxicological studies has revealed risks to pollinator health, particularly affecting honeybees and wild bees, as well as concerns regarding soil and water contamination [41,76]. As a result, neonicotinoids were never widely adopted for locust control and remain excluded from the FAO’s recommended list of operational insecticides [49]. Their use has largely been abandoned in favor of safer compounds [76].

Spinosad: Spinosad, derived from the soil actinomycete Saccharopolyspora spinosa [77], was first evaluated for locust control in 2004 as a bio-derived alternative with a favorable ecotoxicological profile [49]. It acts primarily on the nicotinic acetylcholine receptor, offering rapid knockdown with low mammalian toxicity [49,77]. Field trials have shown encouraging results in terms of efficacy and safety, but its integration into large-scale operational campaigns has so far been limited [50]. Despite spinosad not being approved as a control agent against locusts, the LPRG recommended further efficacy trials in 2023 [43].

The progression of chemical control strategies in locust management illustrates an ongoing equilibrium between effectiveness, cost-efficiency, and sustainability [23,40]. Organochlorines, such as dieldrin, achieved near-complete control but were discontinued due to their ecological toxicity [40,54]. Although organophosphates and pyrethroids are cost-effective and efficient, they continue to pose health and environmental concerns and are subject to increasing regulatory constraints [41,43,48,49,50,66,67,68]. Insect growth regulators (IGRs), fipronil, and spinosad represent the potential of more selective compounds; however, their adoption has been hindered by slow action, ecological side effects, or high costs [41,43,47,49,50,62,74,75,78]. The Food and Agriculture Organization’s Locust and Other Migratory Pests Group (LPRG) has played a crucial role in advocating for safer and more sustainable options [28,32,41,43,48,49,50,60,61,62,63]. Nonetheless, the absence of new compounds under evaluation underscores a concerning reliance on outdated chemistries [43]. Ultimately, while chemical control remains essential in crisis response, excessive dependence on broad-spectrum insecticides perpetuates ecological risks [41,43]. Future initiatives must prioritize investment in safer alternatives, large-scale validation of bio-insecticides, and the integration of chemical tools into preventive, ecologically sound frameworks.

8. Biological Control

Biological control has gained recognition as a sustainable alternative to chemical pesticides, presenting reduced risks to ecosystems, non-target organisms, and human health [16,27,44,52,79]. Since the 1990s, the Food and Agriculture Organization (FAO) has advocated for research into biological agents [62], leading to the inclusion of Metarhizium acridum in the Locust and Other Migratory Pests Group (LPRG)’s list of approved control agents [43,78].

Main Biological Approaches

Natural enemies: Locust eggs, nymphs, and adults are subject to predation and parasitism by a variety of organisms, including birds, mammals, mites, and hymenopteran wasps such as Scelio spp., with parasitism rates occasionally surpassing 25%. Despite this, their effectiveness in curbing large-scale locust plagues is generally inadequate [68].

Botanical insecticides: Extracts from neem (Azadirachta indica), garlic, and cumin have demonstrated repellent and toxic properties [26,55,62,80], yet inconsistencies in their composition and delayed action reduce their dependability in field applications [26,62].

Semiochemicals: Pheromone-based methods hold promise for monitoring or disrupting locust aggregation, with compounds such as phenylacetonitrile being explored [26].

Entomopathogenic microorganisms: Since 1994, Metarhizium flavoviride has been identified as a promising biological control agent against locust hoppers and adults in small-scale settings, particularly in ecologically sensitive regions [32,47,62,68,78,81]. Since 1999, it has been referred to as Metarhizium anisopliae var. acridum, and IT is currently known as Metarhizium acridum [48]. This fungus has emerged as a leading biopesticide, achieving 80–90% mortality within 2–3 weeks under optimal conditions and exhibiting strong environmental safety [26,41]. Commercial products like Green Muscle^® are now being utilized in certain areas [6,41,43,81,82]. Moreover, microsporidia (Nosema locustae), bacteria (Serratia marcescens, Bacillus thuringiensis), and viruses (Entomopoxvirus) have shown experimental success [68], but issues with formulation, stability, and large-scale production limit their practical application [56,62,63,83]. Furthermore, nematode species such as Steinernema sp. and Heterorhabditis bacteriophora have been shown to infect locusts [68,84,85], with laboratory studies indicating high mortality rates [85]. However, their susceptibility to UV radiation and desiccation restricts their use in arid environments. Biological control remains the most promising strategy for sustainable locust management, yet its widespread adoption is limited [84,85].

Operational efforts continue to rely heavily on chemical pesticides due to the slower action, logistical challenges, and higher costs associated with biological alternatives. The case of M. acridum illustrates both the potential and the limitations: while it is safe and effective in trials, its adoption has been slow outside of donor-funded initiatives [6,41]. Increased investment in formulation technologies, long-term field research, and integration with monitoring systems is essential to transition biological control from experimental to mainstream use [6,41,44].

9. Locust Harvesting for Consumption

Harvesting locusts for food and feed has been increasingly advocated as a sustainable complement to conventional management strategies, offering the dual benefits of reducing pest populations and providing a valuable protein source [35,51,86]. Locusts are highly nutritious, comprising up to 60% protein along with essential amino acids, fatty acids, vitamins, and minerals [86,87,88,89,90], rendering them suitable for animal feed in aquaculture, poultry, and pig production [87,89,91]. In humans, entomophagy has a long-standing tradition in Africa, Asia, and Latin America [86,87,88,90], where over 120 locust and grasshopper species are consumed [90]. Swarming behavior facilitates large-scale harvesting [35,86], particularly at night when the insects are less active [35]. Recognizing their nutritional and sustainability potential, the European Commission authorized migratory locust (Locusta migratoria) products as novel foods in 2022 [74].

While harvesting presents a promising dual benefit of pest control and food security, its large-scale adoption encounters several challenges. The outbreak-driven availability renders it an unpredictable protein source, cultural resistance in many regions impedes broader acceptance, and pesticide contamination in wild-caught locusts raises safety concerns [86,87,88,90]. Consequently, locust harvesting should be considered a complementary tool within Integrated Pest Management (IPM), rather than a substitute for preventive or chemical control strategies [90].

10. Future Challenges

Despite advancements in institutional frameworks and technological innovations, the control of locust populations continues to encounter substantial challenges. These challenges pertain not only to the biological characteristics of the pest but also to systemic issues related to governance, funding, and the adoption of technology [6,10,19,23,36,37,92].

10.1. Preventive Control and Early Warning Systems

Preventive control is widely acknowledged as the most sustainable and cost-effective approach to locust management [6,23,40]. It is crucial to note, however, that preventive control does not equate to absolute outbreak prevention [5,20,22]. Outbreaks are an inherent aspect of locust ecology and cannot always be averted [1,4,5,6,7,8,22,23,45,93], particularly for species with extensive distributions such as the desert locust (Schistocerca gregaria) or the Australian plague locust (Chortoicetes terminifera) [11]. Instead, as originally conceptualized by Uvarov, preventive control emphasizes early detection and timely intervention in outbreak-prone areas to curtail population growth and, most importantly, to safeguard major agricultural regions from catastrophic losses [5,22,23,24,25].

The empirical evidence from preventive programs demonstrates both their potential and their limitations. For species with relatively confined outbreak areas, such as the red locust (Nomadacris septemfasciata), the African migratory locust (Locusta migratoria migratorioides), and the South American locust (Schistocerca cancellata), preventive strategies have successfully averted plagues for extended durations, in some instances for decades [10,11,36]. Conversely, for more widely distributed species, preventive management has mitigated the magnitude, frequency, and duration of plagues, though it has not eradicated them. This distinction highlights why equating preventive control with outbreak prevention fosters unrealistic expectations and risks undermining confidence in otherwise effective programs [3,5,11,23,40].

Despite its conceptual clarity, the implementation of preventive control continues to encounter systemic obstacles. Historically, Uvarov’s strategy of continuous surveillance and early intervention has been compromised by a “boom-and-bust” funding cycle: donor resources increase during crisis periods but diminish during recessions, leaving national programs inadequately resourced for sustained surveillance. This financial instability, combined with governance challenges and political instability in several frontline states, undermines the capacity to maintain the constant vigilance necessary for effective prevention [6,10,17,36,37].

Concurrently, technological advancements have significantly enhanced the tools available for early warning systems. Innovations such as satellite imagery, UAVs, GIS mapping, and machine learning now provide unparalleled capabilities to monitor breeding conditions, detect hopper bands, and forecast gregarization risk [2,3,5,13,15,23,40,94]. However, the operational adoption of these technologies remains inconsistent. Numerous affected countries lack the necessary infrastructure, connectivity, and technical expertise to fully implement these tools, and in regions affected by conflict, even basic field surveys may be disrupted [6,10,17,36].

Looking ahead, the primary challenge is not merely to prevent outbreaks but to consolidate and enhance preventive control as a comprehensive system of early warning and early action. Three priorities are essential:

• Institutional reforms are necessary to ensure stable, inter-plague funding for surveillance and control, rather than relying solely on emergency aid.
• It is imperative to bridge the technology–capacity gap through training, infrastructure development, and equitable access to advanced monitoring systems.
• The integration of predictive analytics into decision-making processes, utilizing models that incorporate ecological, climatic, and socio-economic variables, is essential for guiding timely interventions.

As [11] emphasizes, the true measure of success lies not in the eradication of outbreaks, but in the protection of agriculture and the mitigation of socio-economic impacts through accurate forecasting and early intervention. Without these systemic changes, preventive control will remain underutilized, and the global community will continue to oscillate between neglect during recessions and crisis-driven reactive campaigns during plagues [11].

10.2. Future Research in Chemical Control

Chemical insecticides are anticipated to remain integral, particularly in emergency situations [6]. Nonetheless, the dependence on organophosphates and pyrethroids is problematic due to concerns about ecotoxicity, the development of resistance, and regulatory limitations [41,49,50,69,70]. Although spinosad and anthranilic diamides are under investigation as more selective alternatives [43], progress in this area remains gradual. Future research should focus on the development of insecticides characterized by reduced environmental persistence, targeted specificity, and compatibility with integrated pest management strategies.

10.3. Future Challenges in Biological Control

Biopesticides, such as M. acridum, have demonstrated safety and efficacy in trials; however, their slow action, limited shelf life, and high costs constrain their large-scale application [41,44]. Other agents, including N. locustae, entomopathogenic bacteria, and nematodes, remain predominantly experimental [84,95]. Future research should prioritize enhancing formulations, scaling up production, and investigating synergies among various biocontrol agents [6,41,44]. Integration with modern surveillance tools could facilitate more targeted and cost-effective utilization [6,40].

10.4. Critical Synthesis

Locust management is currently at a pivotal juncture. While preventive and biological strategies are increasingly acknowledged as crucial for sustainable practices, operational realities continue to necessitate a reliance on reactive chemical control measures. To bridge this gap, three significant shifts are required: (i) the institutionalization of stable funding mechanisms that prioritize prevention over emergency aid, (ii) the assurance of equitable access to advanced monitoring technologies, and (iii) the acceleration of research on selective chemical and biological agents suitable for application at the field scale. Without these systemic changes, locust control is at risk of remaining reactive, perpetuating the costly cycles of outbreak and emergency response.

11. Conclusions

Locust management continues to pose a significant global challenge, exacerbated by the climate crisis, which is anticipated to expand outbreak ranges and intensify swarm dynamics. Following the prohibition of organochlorine insecticides such as dieldrin, significant advancements have been achieved in the development of chemical alternatives, biological agents, and preventive frameworks [5,23,25,26]. The implementation of Ultra-Low Volume (ULV) spraying, UAV-based applications, and novel compounds with enhanced ecotoxicological profiles has mitigated some risks associated with older chemical formulations [23,40,81]. Concurrently, the successful development of M. acridum and advancements in monitoring and forecasting models have contributed essential components for more sustainable control [2,6,23,40,41,44].

The institutionalization of locust control, through the establishment of FAO-led frameworks and regional commissions, has facilitated international collaboration and the standardization of protocols [6,43]. Nevertheless, significant weaknesses persist. Preventive strategies, although conceptually robust, remain underfunded and inconsistently applied, resulting in many countries being caught in a reactive cycle of “recession neglect” followed by costly crisis response [6,17]. Biological agents, despite their potential, encounter challenges related to cost, slow action, and production logistics, hindering their large-scale adoption [6,37,41,44].

In considering future directions, the primary challenge lies not merely in the discovery of novel tools but in the structural reorganization of locust management systems. Three priorities are evident: the establishment of stable financing mechanisms to support preventive surveillance during economic downturns; bridging the technology–capacity gap by ensuring that innovations such as remote sensing and machine learning are complemented by local infrastructure and training; and the integration of selective chemical and biological tools within preventive frameworks to enable environmentally safer and more targeted interventions. In summary, while locust management has made significant advancements over the past century, it remains reactive and fragmented. Without sustained institutional commitment and investment in sustainable technologies, future responses will likely perpetuate the costly cycle of crisis and emergency control. Transforming management into a proactive, integrated, and ecologically grounded system represents both the greatest challenge and the most urgent priority.