Recent progress in Desert and Migratory Locust management in Africa. Are preventive actions possible ?
LECOQ M., 2001. Journal of Orthoptera Research 10(2) : 277-291.
CIRAD, Center for international co-operation in agronomic research for development, Prifas, TA40D, Campus international de Baillarguet, 34398 Montpellier cedex 5, France, e-mail : michel.lecoq@cirad.fr
Abstract
Locust control in Africa has been the focus of considerable controversy over the last 15 years. Many aspects were called into question following the last large plagues of 1987-88 (Desert Locust) and 1996-2000 (Malagasy Migratory Locust), starting with the hitherto recommended preventive strategy, along with the environmental impact of insecticides used, and even the real socioeconomic importance of the locusts. Many projects were launched to improve survey and control methods and find alternative solutions to chemical pesticide treatments. Recent progress are reviewed. Survey and application techniques suffered dramatic improvements with GIS, GPS technology and precision spraying. Barrier applications are again available thanks to new persistent pesticides. Biological control with mycopesticides now appears very promising and undoubtedly the technique will gradually be adopted. The environmental aspects are taken into better account. An IPM approach is now possible. The EMPRES program of FAO is committed to reinforcing national early warning and early reaction capacities for preventive control of the Desert Locust. In Madagascar a new National Locust Center has been recently set up. Everywhere local research capabilities are improving. However, certain very fundamental aspects remain unsolved. Among others, the sustainability of preventive control systems is an important concern. Many affected countries are amongst the poorest in the world. They currently do not have sufficient financial resources to fund intensive control campaigns, nor even the basic minimum to ensure prevention. A realistic solution to prevent locust plagues requires stronger commitment of governments and donors, sustainable light but flexible national locust control units for prevention, and especially the creation of emergency action plans ready to quickly mobilize and organize complementary resources in the event of an upsurge. Emergency funds are thus essential and should be created. Locust control seems now to depend more on political and institutional choices than on scientific and technological innovations.
Key-words
Acrididae, locust control, outbreaks, Desert Locust, Migratory Locust
Introduction
Throughout history, humanity has always been affected by locust plagues, and these plagues have always been particularly devastating for Africa. During the past centuries, this remained a recurrent theme for travelers, missionaries and naturalists… who all bore witness to the severity of the problem and its effect on food supplies on this continent. Means of controlling these plagues long remained rudimentary : noise, fire, prayer, etc. However even today this is still quite often all certain populations can do.
Organized control of locust plagues started as soon as agricultural resources were methodically exploited in colonized countries (Roy 2001). The first scientific study on the subject and the first control campaigns took place in Algeria during the second half of the 19th century (Buj Buj 1995). Jules Künckel d'Herculais' pioneering work (1905) marked the first European action in Africa in the fight against the locust. This research helped to increase international awareness of the problem. However, it was not until October 1920 that there was a first attempt at international co-operation through the International Conference on the Organization of Locust Control in Rome, which was held under the patronage of the International Institute of Agriculture. We all know the development of this international co-operation and the resulting progress. All this was of course boosted by the efforts of Boris P. Uvarov and other pioneers amongst whom especially Boris N. Zolotarevsky (Uvarov & Zolotarevsky 1929) and Paul Vayssière who played a fundamental role in the internationalisation of locust control in Africa (Vayssière 1924).
Alongside this co-operation and as early as the second half of the 19th century, scientific knowledge on the subject increased and modern control techniques appeared and were continuously improved. The greatest progress was certainly achieved between 1930 and 1950 (Jago 1998). Within a few decades, both a good understanding of the locust problem in Africa and constant improvement of its management were achieved, both from a technical and institutional point of view, with the setting-up of national and regional locust management organizations, the development of international co-operation, the enforcement of a preventive strategy as well as more effective control techniques.
Yet, the current situation is paradoxical. While we have never had so much scientific knowledge on the causes of locust plagues, as well as ever more sophisticated means of control, the last few years have shown us that locust control in Africa is totally questionable. A significant locust plague shook numerous African countries in the late 80s with substantial grasshopper outbreaks followed by a plague of Desert Locusts. More recently, a plague of Migratory Locusts and red Locusts heavily affected Madagascar. As a consequence of these events, many questions arose regarding techniques for handling pest locust populations, and even the extent of the locust problem and the effectiveness of locust control operations were questioned. However, it is certainly these questions that have led to extensive research work and substantial progress over the last 10 or 15 years. The Desert Locust and the Malagasy Migratory Locust may be used as examples to explain this progress, prospects for the future and bring up some key questions that remain unsolved.
1. Basis and hazards of plague prevention
Both regarding the Desert Locust and the Malagasy Migratory Locust, preventive strategy is based on a wide knowledge of the biology and ecology of each of these species, and particularly on precise knowledge of their outbreak areas (Fig. 1). Technically, this preventive strategy requires :
- Monitoring and early warning capacities
- Early reaction capacity, to control transient-to-gregarious populations.
In the case of the Desert Locust, this strategy also supposes effective international co-operation, both regarding monitoring and control, given the great number of countries involved. Therefore, there is a basis for prevention ; this basis is ancient and founded on research work that first began around one century ago. This strategy has been used for around 40 years, especially by the FAO (FAO 1968, 1972 ; Hafraoui & McCulloch 1993).
The enforcement of this preventive strategy has helped to prevent great plagues and to reduce the frequency of upsurges (Skaf et al. 1990 ; Roy 2001). Figure 2 shows, for the Desert Locust, successive periods of plague and upsurge over the last 120 years. From the 1960’s, we can observe - a time when control techniques became more effective and when prevention was implemented - a significant drop in the frequency of plagues. This fact is usually mentioned as proof of success in preventive management, even though the influence of climate changes and extreme dry conditions that prevailed in Africa during the period should not be forgotten (Major 1994).
Nevertheless, the same phenomenon can be observed in Madagascar in the case of the Migratory Locust, a species which evolves in an ecological environment completely different to that of the Desert Locust (Fig. 2) (see Lecoq 1995 for scientific basis of plague prevention in this country). In this case, it is impossible to incriminate dry conditions. Similar developments, both in Africa and in Madagascar, strongly support the preventive control and modern control methods to the detriment of the climate change theory. In one case as in the other, the end of large plagues in the early 1960’s corresponds to better knowledge on the subject, the implementation of a preventive strategy, a more effective monitoring system and new control methods, especially ULV drift applications, barrier applications and the use of a persistent organochlorine insecticide, dieldrin. Thus, within a few years, all these improvements fundamentally changed the operational problem and led to greatly improved outbreak control (FAO 1968 ; Roy 2001).
Yet recently, plagues have made a comeback. The last 15 years have once again seen Africa under serious attack by locusts ; from 1987 to 1989, a Desert Locust plague (Skaf 1988 ; Skaf et al. 1990 ; Showler & Potter 1991) affected numerous countries. Swarms from the Red Sea region migrated to the Sahel and North-West Africa following seasonal winds and rains. In October 1988, some swarms crossed the Atlantic to reach the Caribbean and the northern part of South America. Between 1996 and 2000, this was the case for the Malagasy Migratory Locust (World Bank 1998 ; Duranton et al. 2000). Within 3 years, the whole island was invaded ; even the eastern forest zone was affected and only the far North of the island was spared. Massive swarms were observed. In 1998, at the height of the plague, average swarm size was 4000 hectares (Fig. 3). Wide-scale control operations were relentlessly carried out for 3 years with substantial air means and significant international assistance and obviously, intensive use of insecticide ; this had consequences for the Malagasy environment, both very rich in endemic species and very protected (Schulten et al. 1999).
Globally, the costs for combating these plagues were colossal : over $300 million for the Desert Locust, and over $50 million for the Malagasy Migratory Locust. Huge surface areas had to be treated (although incomparable to what should have been preventively treated). Between 1986 and 1989, $26 million hectares were treated against the Desert Locust in 23 countries. The banning of dieldrin necessitated full coverage sprays, often used in a repetitive way and with non-persistent insecticide such as fenitrothion and malathion. Such treatments possibly had a more serious environmental impact than the organochlorine-based treatments they replaced (Rowley & Bennet 1993). In Madagascar, more than 4.2 million hectares were treated during the latest plague (1.2 in full coverage mostly with deltamethrin, propoxur and fenitrothion and the remaining 3 million hectares in barrier applications with fipronil) (Lecoq 2000a).
What are the reasons for the return of the plague and what lessons can be drawn from this ? Is it a failure in strategy, inappropriate control methods or a lack of knowledge about the problem ? The answer is extremely straightforward : it is the consequence of an overly long remission period. Both in Africa and in Madagascar, from the 60s, the relative calmness of the locust situation gradually brought about a decline in support to regional management organizations (such as OCLALAV and DLCO-EA) and to national locust control units (Gruys 1994 ; Lecoq 1991). In fact, these recent plagues were forecast at a very early stage. However, the countries’ reaction capacity was substantially weakened, which made it impossible to stop upsurges when they started. They then had to accept the gravity of the situation, the need for action through chemical control due to a lack of other methods by going beyond such issues as product-choice and mobilizing the required international resources. By the time all conditions were met, the problem had already increased in scale and there was a plague. Africa witnessed exactly the same scenario in 1987 as did Madagascar in 1997. Obviously, other reasons could be put forward, especially, as regards the Desert Locust; security problems, wars, terrorism etc, made access to certain zones difficult or even impossible (Showler 2001a). Nevertheless, the basic problem remains the global weakening of control organization.
The consequence of the return of the plague, and especially of this first "locust shock" in 1987, was global questioning, mainly influenced by the so called "donor" countries, financially solicited during periods of plague (Joffe 1995 ; Rowley & Bennet 1993 ; US Congress 1990 ; Van Huis 1994b). Questions, among others, were centered on:
- the real economic importance of locusts (numerous decisions were taken both on the basis of political and emotional considerations as well as objective risk assessment regarding agricultural production and food safety)
- the preventive strategy (blamed for lack of clarity and consistency) and its efficacy
- Leadership and the FAO view of the problem
- the choice of the all-insecticide solution given its impact on the environment
- the feasibility and efficacy of biological control methods
- countries' capacities for long-term control given their financial resources
- the true point of control in the face of possible alternative solutions ?
And finally, the advantages of not reacting to an outbreak were considered.
Rightly or wrongly, in the 1990’s, many estimated that the time had certainly come for a change of approach to the locust problem. The positive aspect of this questioning is that, over the last 10 years, much research has been done, resulting in great progress in very diverse fields (see for example, Krall & Wilps 1994 ; Krall et al. 1997 ; Lomer & Prior 1992).
2. Recent progress in Desert and Migratory Locust management
2.1. Economic impact of acridids
The economic impact of acridids became a subject for much discussion and study. The aim was to better assess this impact - often considered as over-estimated - and in particular to know if it was not overvalued, given the spectacular nature of the plague phenomenon and the resulting inevitable political pressure. It was also necessary to know if preventive control was an economically viable option.
Better estimates of the economic risk are now available, especially regarding the Desert Locust. Yet, these estimates still have to be refined (Bullen 1969 ; Krall 1994 ; Herok & Krall 1995 ; Joffe 1998). Although damage is unlikely to pose a threat to global food supplies in any country, locally, it can be considerable. The probability of annual damage running into tens of millions of US dollars is far from negligible. In addition, damage to pastures is not taken into account in current models. Furthermore, even though the value of lost harvests is low in financial terms, the consequences of plagues can be serious in certain cases and cause significant disruption in the local economy.
A recent study provide a conceptual framework for economic evaluation of Desert Locust management interventions (Hardeweg 2001). This economic approach will have to be pursued, since numerous donors base their financial support on this information. Unfortunately, simplistic positions are too often observed, in which support depends on the extent of damage or where it is considered that money for support has been wasted if no damage has been reported ; this is totally in opposition with the notion of prevention and the attempt to reach effective control operations.
The debate on the economic importance of locusts does not date from today. At the end of the 19th century, Kunckel d'Herculay (1905) already struggled to justify control operations against the Desert Locust in Algeria. Five large plagues occurred during the 20th century and in one century, there were 50 years of plague. The problem is thus major. However, risk estimates - reliable and accepted by all - are not yet widely available and the same problem of economic justification periodically arises. Today, financial support for desert locust control remain a controversial issue in international development circles.
We know, however, that the locust problem cannot be reduced to a simple economic equation. Classical cost-profit analyses are inaccurate in the case of migratory insects, since control operations can be funded by certain regions to benefit very remote regions.
Lastly, it seems that, whatever the cost-profit relation, locusts should be and will be controlled since other aspects, in particular social and thus political, have to be considered - the economic aspect being only one of the elements. Moreover, some believe that "accurate estimates of the benefits of the control are unlikely to be possible in Africa" (Lomer et al. 2001).
2.2. Management strategy for the locust problem
This was one of the main areas of controversy. There were many debates on the strategy to adopt in order to reduce the economic and environmental costs of locust control to acceptable levels. Some advocates attempted to tackle the source of the problem and to prevent upsurges ; others to control upsurges (Major 1994 ; Skaf et al. 1990) and others limited action to close protection of crops without preventing plagues.
Some experts have advised treatment of developing swarms as the most cost-effective option (Symmons 1992). After many debates (see e.g. Van Huis 1994a), the direction currently pursued is the development or the reinforcement of national monitoring and early reaction capacities in order to treat as quickly as possible. Past experience has always shown that the longer we wait, the greater the risk of being overwhelmed by the plague. Furthermore, as regards the Desert Locust, a comparison of recent control campaigns has shown that early reaction in the first breeding zones is directly linked to better control of upsurges (Showler 2001b).
Finally, after a decade of questioning, it seems that preventive control is again considered as the most effective option ; the least costly and the least damageable to the environment but also as a strategy which helps develop the required skills and infrastructures in the countries concerned. This issue is of prime importance as it can help these countries, in the long run, to manage the locust problem and to diminish their dependence on external support (FAO 1994, 2001 ; Martini et al. 1998 ; Showler 1997 ; Showler & Potter 1991).
2.3. Monitoring and early warning
In terms of monitoring and early warning, recent progress has been made in the fields of biogeography, GIS, space remote sensing and communications.
The long remission period made it possible to obtain a much more precise image of the distribution of the plague generating transient populations. This was particularly the case for the Desert Locust, where identification of potential zones for gregarisation improved ; zones which require priority monitoring as part of a preventive strategy (Popov 1997 ; Popov et al. 1991). Therefore, better tools are now available to monitor the most important zones.
Means of communication have undergone improvements thus benefiting locust control. The locust situation in a given country can now be transmitted via Internet in data base form. In addition, FAO signaling and forecasting updates are transmitted by e-mail and available and regularly up-dated on the Internet.
A great amount has been done in the field of geographic information systems (GIS). It is now possible to integrate into a computer system the various data on locusts, on their environment - particularly rains. This data can be better used and interpreted for more effective forecasting. GIS already exists for the Desert Locust. There are two versions ; the more sophisticated one, developed on a workstation, is managed by the FAO in Rome and covers the entire breeding area of the Desert Locust [SWARMS, Schistocerca Warning Management System]. Simplified versions, which work from portable computers, are being installed in each country [RAMSES, Reconnaissance and Management System for the Environment of Schitocerca] (Cressman 1997 ; Magor 1993 ; Magor & Pender 1997 ; Rosenberg 2000). A geographic information system is being developed for the Malagasy Migratory Locust. Along with a forecasting model of risk situations, this should be a real decision-support tool to organize monitoring and treatment operations.
Space remote sensing is also a technology that has brought about substantial advances. For the Desert Locust, satellite data - SPOT VEGETATION, METEOSAT and NOAA satellites - are used to better localize zones of rain and developing vegetation which may favor locust breeding, thus guiding the ground survey teams (Cherlet 1993 ; Cherlet & Di Gregorio 1991 ; Voss & Dreiser 1997). Various problems continue to arise which perturb early identification of vegetational cover in the case of low coverage, typical of the Desert Locust breeding areas where desert vegetation is often very sparse or very localized, at the heart of very small wadis. Much improvement can still be made, but this is a key point. The prevention issue is above all a question of information. In both the case of the Desert Locust and the Malagasy Migratory Locust, prevention lies primarily in efficient real-time data entry of field information on the quality of the environment. Ground networks are not sufficient and only more precise interpretation of satellite imagery will bring improvement. Despite a few recent failures, it is one of the directions to pursue and all the more so since technology is constantly evolving and new sensors continuously appear.
2.4. Locust control
Progress affects both products in use and survey and application techniques.
Main pesticides
As a result of the banning of organochlorines and especially dieldrin, current locust control operations are mainly based on organophosphorous (such as fenitrothion and malathion), carbamates (such as bendiocarb), pyrethrinoids (such as deltamethrin and lambda-cyhalothrin), but also on more recent products such as insect growth regulators (IGR) with dimilin and triflumuron, fipronil and more recently imidacloprid (FAO 1999). Therefore, a wider range of chemicals, less toxic than previous products, especially organochlorines, is available - even though obviously, they continue to raise risk issues for the environment, particularly in sensitive and protected zones.
Survey and application techniques
Application techniques have become more efficient and safer both for operators and the environment. The recent invasion of the Migratory Locust in Madagascar was the opportunity to put this new technology into practice on a wide scale.
Applications are usually made according to the Ultra Low Volume treatment technique (ULV), which is certainly the most effective way of applying insecticides (Matthews 1992). This is not a recent innovation since it dates back to the 1950s. What is new, on the other hand, is the attempt to evaluate and minimize the impact of locust control on the environment. Chemical control generated wide environmental concern, due to the large amounts of insecticides used and to their negative impact on nontarget fauna (Berger et al. 1991 ; Ritchie & Dobson 1995). Much data relating to this impact has been obtained in Africa, especially through the LOCUSTOX project (Everts 1990 ; Everts et al. 1997, 1998, 1999). In fact, the most harmful side effects could be avoided by following the FAO directives for application and by carefully selecting insecticides (Ritchie and Dobson l.c.). Furthermore, over and beyond the impact of products is the strategy pursued, which is undoubtedly as important, if not more so. The best environmental safeguard is obtained by applying a preventive strategy which, through applications over small surface areas, prevent the outbreak of plagues and thus the need to treat much wider areas.
Undoubtedly the greatest progress made recently was that of the precision of applications. The use of GPS technology (and especially of differential GPS or DGPS) - i.e. a positioning technique guided by satellite – has revolutionized locust control by :
- securing navigation, in particular in the case of desert zones frequented by the Desert Locust;
- improving survey by recording the precise co-ordinates of target locust and transmitting them to spray aircrafts ;
- substantially improving precision spraying ; precision to within several meters can be achieved both to locate targets and to pilot spray aircrafts (the GPS guides the navigation of the spray craft so it follows exactly the desired route to within a few meters, at the desired speed, respecting precisely the width between each passage without using ground beacons. As far as on-board computing is concerned, it automatically controls the rate of the insecticide and reaches great precision in the doses spread over one hectare) (Fig. 4, 5).
The use of these navigation systems is likely to be generalized in locust control (Ottesen et al. 1999 ; Dobson 1999).
Another fundamental issue over the last years has been the possibility to reintroduce barrier applications (Cooper et al. 1995 ; Rachadi & Foucart 1999 ; Scherer & Rakotonandrasana 1993). The strategy of preventive control had been weakened as a consequence of the banning of dieldrin (Skaf et al. 1990). The recent launch on the locust control market of chemicals such as the IGR or fipronil - which also present persistence properties - now makes it possible to reintroduce the barrier technique and thus reinforces the efficacy of the preventive strategy. We can recall the numerous advantages of the barrier application technique :
- rapid treatment of a much wider surface area (and for prevention, the time factor is known to be fundamental in curbing upsurges) ;
- the amount of chemicals spread on one protected hectare is lower ;
- given the non-treated zones between barriers, the impact on nontarget fauna is lower
- substantial savings can be made by reducing both flight time and the amounts of insecticide spread.
Efficacy of chemical control
Several questions have arisen regarding the real efficacy of chemical control to manage locust outbreaks (i.e. Pesticide Trust 1998). However, chemical control methods have shown their efficacy many times over. There has never been a confirmed case of resistance as is sometimes stated (such would-be cases are very often due to bad application techniques). Furthermore, although various natural factors may stop the course of invasions, the results of control operations must also be taken into account. These natural factors played an important role in the early curbing of the Desert Locust plague in 1989 ; the real impact of massive operations of chemical control remains in this case difficult to estimate and all reported evaluations are still very biased. The positive impact of chemical control can be more easily demonstrated in the case of the recent Malagasy Migratory Locust plague. From 1998 to 2000 - as control effort was pursued - a gradual reduction was seen in the contaminated surface area, the number, the size and density of swarms. The average size of swarms was 4000 hectares in 1998, down to 1000 in 1999, only 250 hectares in 2000 and eliminated in 2001 (Lecoq 2000a).
In addition, it was observed that recent plagues - of both desert and Malagasy Migratory Locusts - stopped or were stopped within 2 or 3 years whereas they lasted much longer in the past (10 to 20 years). Moreover, over the last 40 years, several major upsurges were quickly nipped in the bud thanks to timely chemical control campaigns. However, despite the efficacy of chemical control, there is still high demand for alternative solutions.
2.5. Alternative methods
Botanicals
Varied research on vegetal extracts (Neem and Melia volkensii) have been or are being carried out (e.g. Krall & Wilps 1994). They are still at the experimental stage as far as locust control is concerned. Large-scale production is still problematic and difficulties with the registration of a variable product will limit adoption (Meinzingen & Kooyman 1997). The use of such products seems to be aimed at locally protecting crops.
Semiochemicals
Recent research, in particular by the ICIPE teams in Kenya, revealed in the Desert Locust a very rich system of neurotransmitters that act at all levels of the insect's life. At the monitoring stage, the use of pheromones may be considered. Pheromone traps could detect population growth at the transient stage - which is very difficult to study - and thus improve the preventive strategy by better forecasting the outbreak of upsurges. Moreover, pheromones can be used as a means of control, by making locusts transient and more sensitive to predator attack or by increasing their sensitivity to sublethal doses of insecticide (Hassanali & Bashir 1999). The pheromone phenylacetonitrile inhibits pheromonal communication among gregarious hoppers and induces stress which can lead to high mortality. This pheromone could be an alternative control agent to conventional pesticides. It costs very little per hectare treated and could cut control costs enormously. Field experiments have already been carried out, but there is nonetheless still much to do in this area. Practical applications seem far off and an operational strategy based on the use of such products is still to be defined. Current research is unlikely to lead to applications before several years.
Mycopesticides
Currently, the best solution to replace synthetic insecticides is undoubtedly the use of mycopesticides (Goettel M.S. & Johnson D.L. 1997 ; Lomer & Prior 1992 ; Prior 1992 ; Prior & Greathead 1989). These products are composed of spores of pathogenic fungus. The recent development of effective oil formulations of Metarhizium anisopliae spores in Africa (but also in Australia, Brazil and other countries) opens up new possibilities for environmentally safe control operations. Metarhizium biopesticide kills 70-90% of treated locusts within 14-20 days, with no measurable impact on nontarget organisms (Kooyman et al. 1997 ; Lomer et al. 2001). These products act slowly and are thus inaccurate for emergency situations. However, they should have a role in an integrated control strategy alongside classic insecticides (Lomer et al. 1999). They are now available on the locust control market and are now part of the FAO list of products recommended for locust control (1999).
Other alternative solutions
Some consider that there has been overemphasis on locust control, mostly using chemical pesticides and that control of locust populations by chemical or non-chemical means is only one of several options of risk management (Joffe 1995, 1998). Some other alternative solutions for the locust problem are :
- do not react and use locust control funds to intensify agricultural production
- supply food assistance or any other more appropriate assistance
- recommend that farmers take out anti-locust insurance policies.
Such alternatives are still studied and some consider farmer insurance as a competitive strategy. For many involved in locust control, they nonetheless appear somewhat unrealistic - and little adapted to the economic and social reality of most countries concerned.
2.6. An IPM approach ?
A few years ago, it could be said that the ultimate objective of locust control was to adopt an Integrated Pest Management (IPM) approach. During the last 10 years, great progress has been made and from now on, it is possible to apply some of the principles of integrated management to desert and Migratory Locusts. For this, the following tools are necessary :
- a full knowledge of the dynamic of populations
- monitoring and forecasting networks to better control the evolution of populations and react in time
- models that determine the efficacy and the cost of different control options
- action thresholds
- a diversity in insecticides that makes it possible to combine them to limit impact on the environment
- recently, it became possible to use biological products in addition to insecticides
- lastly, follow-up methods for the environmental impact of control operations.
Thus, a full range of complementary methods are available, which supposes that we are now progressing towards an integrated approach (in the IPM sense) to the locust problem in Africa.
3. Recent institutional developments and the reinforcement of monitoring and preventive control
The last 10 years have seen a positive development with an institutional renewal, the beginning of reinforcement of control capacity and the development of regional co-operation.
As far as the Desert Locust is concerned, the most remarkable fact is undoubtedly the launch of the huge EMPRES program initiated by the FAO. This program is the logical consequence of the 1987-1989 plague, mainly due to the gradual weakening of states' capacities to carry out preventive operations. The first part of the program has been operational since 1996 in the central region of the breeding area of the Desert Locust, in countries around the Red Sea. The second part concerns West and North-West Africa and began in 2001. One of the priorities of the EMPRES program is to strengthen the monitoring and control capacities of countries in which there are outbreak areas in order to help them conduct efficient preventive operations (FAO 1994, 1995, 2001 ; Martini et al. 1998).
The other EMPRES priority is the development of regional co-operation. From this point of view, the second important and highly significant event of the last few years is the creation of the Commission de lutte contre le Criquet pèlerin en région occidentale (CLCPRO) which, in the long run, should play the role of two former organizations for regional co-operation : the Commission de lutte contre le Criquet pèlerin en Afrique du Nord-Ouest (CLCPANO) and the Organisation commune de lutte antiacridienne et de lutte anti-aviaire (OCLALAV) for Sahelian countries (FAO 2000 ; Lecoq 2000b). It is one of the major events in recent years. The Commission, which was created in 2000, should provide much improved co-operation between the 9 countries of the occidental region directly involved in the coordination of Desert Locust preventive control. This change in the institutional system is an important factor demonstrating the will of those states interested to preserve – with the support of the FAO – an operational system of Desert Locust preventive control.
In Madagascar, after the last plague, positive institutional developments were also made with the creation in 1999 of a new “Centre National Anti-acridien” (National Locust Center) aimed at replacing the former structure with more independence and wider possibilities of action.
4. Prospects and sustainability of preventive control
Undeniable scientific and technical progress as well as positive institutional development have been visible over the last decade. A number of indicators show things are moving in the right direction. However, is all of this sufficient and sustainable ? In fact, the question is : “Are we not making the same mistakes as in the past ?” These mistakes can be represented by what has been referred to as the anti-locust vicious circle, with periods of plague and motivation alternated with remission periods that provoke gradual disinterest. It is a classic scheme that has been regularly mentioned over decades. Nevertheless, it is the real – and recurrent - problem that weighs on the efficacy of preventive strategy.
Hence :
- some donors who fund locust control question the setting-up of a system that will certainly collapse during remission period
- the countries’ long-term capacity to bear the weight of the recurrent costs of the preventive control system is also questioned.
How can sustainability be ensured ? The following important points should be considered as being vital for sustainability :
• Continuous commitment of the states involved
• A fundamental locust control structure, which should be as light as possible, and thus less costly and sustainable for countries involved
• A system that can be modulated to the locust situation and that can be rapidly reinforced when necessary
• Emergency plans for exceptional situations - this is essential given the extent of lands to monitor and the diversity of those involved
• Identified reserve funds
• In the case of the Desert Locust : coherent regional co-operation both at technical and financial levels (certain countries carry out preventive control without benefiting from it ; others do not, but do benefit)
• Modest – but continuous – funding from donors, for whom an efficient preventive system means less frequent, less costly and better organized emergency action.
In fact, difficulty in ensuring long term support from governments and donors for programs of preventive control is one of the major problems to solve, since it could lead to failure in controlling future upsurges and to the development of new plagues. The support of donors will remain particularly problematic as long as the current debate on the economic importance of locusts and the best pest management strategy is not over. The risk is that the differing views of experts, donors and affected countries on the subject slow down the implementation of coherent actions.
The key issue of sustainability in locust control should certainly be considered as a subject for research. If solutions to ensure sustainability are not found, any progress made in other areas of locust control will be in vain.
Conclusions
Beyond scientific and technical aspects, the future of desert and Malagasy Migratory Locust control now depends mainly on financial, institutional and political aspects that cannot be controlled by scientists but are the true key issues of locust control.
At the end of the Second World War - during a period of plague and while control methods were much less effective than today - the failure to manage the locust problem was already at that time not put down to a lack of scientific knowledge and technical means, but to a problem of socio-political organization. Fifty years on and we are still faced with the same problem.
Acknowledgments
We would like to thank the Food and Agriculture Organization of the United Nations for allowing us to follow the development of locust control during recent years in Africa and in Madagascar through numerous field missions, and to modestly be part of current developments.
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Figure legends
Fig. 1. Outbreak areas of the Desert Locust and of the Malagasy Migratory Locust.
a. Desert Locust : light and dark grey, invasion area ; light grey, recession area (modify from Popov 1997). b. Migratory Locust : outbreak area and spread of the last invasion from 1996 to 1998 (modify from Lecoq, 1995 and Duranton et al., 2000)
Fig. 2. Plague and recession periods of the Desert Locust and of the Malagasy Migratory Locust, 1880-2000.
Population level : 0, recession ; 1, upsurge ; 2 invasion (source of data : Schistocerca gregaria, FAO, 1994; Locusta migratoria capito, Scherer & Lié Fong Hong 1995)
Fig . 3. Some pictures of the recent Migratory Locust invasion in Madagascar.
Swarms : a, b, c d, f (photo M. Lecoq) and hopper band : e (photo J.-F. Duranton.).
Fig. 4. Map of areas sprayed in 1999 in the southern part of Madagascar : an example of the utilisation of the GPS technology in locust control.
(Source : J.-F. Duranton, P.L.A.A.G. - Project for locust control in the outbreak area, and European Union - Food security program in Madagascar).
This map of the southern part of the island presents areas that received locust treatment between November 1998 and April 1999. For each area, details on sprays and the precise route of spray aircrafts are available. All areas submitted to special environmental protection have been preserved, as shown on the map. These maps may be quickly and easily sent via Internet anywhere in the world, allowing donors to follow current operations. They then can be used as proof of the quality of work carried out.
Fig. 5. Recent example of aerial barrier spraying in Madagascar using DGPS technology (courtesy of AGRICAIR, Zimbabwe)
