The Locust Controversy
—alternatives to chemicals available soon Profile of the UK Agriculture Minister

The French locust research organisation PRIFAS is warning of a possible new plague of locusts in the Eritrea/Red Sea area. FAO held a workshop in May on research priorities in locust control, and a new book on the subject surveys practices and makes recommendations. By Peter Beaumont.

Grasshoppers, locusts and plagues
The devastation that locusts can cause is well-publicised and widely feared. Locusts have the ability to swarm, which occurs when solitary locusts group together and then migrate. The facility to swarm distinguishes locusts from grasshoppers (both belong to the Acrididae insect family) and is largely a function of population density. Following locust outbreaks in the 1950s there were no subsequent serious outbreaks until the 1980s. A plague formed in the period 1986-89, and large stocks of the highly persistent insecticide dieldrin were used to control swarms. 
    The principal strategy was barrier spraying: dieldrin was sprayed across the path that it was hoped marching bands of locust hoppers would take. As the insecticide was persistent, any hopper bands that did in fact cross the barrier strip were killed. In addition to barrier spraying, organphosphorous pesticides, such as fenitrothion, were sprayed from planes overflying a locust swarm. Both methods depended on good information of the whereabouts of the target locusts and the availability of stores, equipment and trained personnel. FAO, as the co-ordinating agency, was criticised over the level of use of pesticides, the problems of dumps of surplus stocks of older pesticides and the efficacy of the campaign.
    A report of the US Office of Technology Assessment (OTA), A Plague of Locusts, summarised the criticisms(1).  In 1986, donors spent approximately US$40 million to control locusts that threatened 3% of crop production in the nine most affected African countries. These efforts saved crops worth an estimated US$46 million, representing three-fifths of the crops threatened, but less than 2% of total crop production. In 1987 and 1988 11 million litres of insecticide—mainly fenitrothion and malathion—were used on approximately 15 million hectares, and in 1988, 11 million litres were used in four northwestern African countries alone. In the end, the swarms dissipated over the western Atlantic: but of course had they returned to land and continued breeding and migrating, the story might have been different.
    Following the 1989 campaign, FAO began to revise its strategy. A Consultative Group for Locust Research (CGLR) was created, which took advice from a Scientific Advisory Committee. It is also guided by the Desert Locust Control Committee. The principal locust causing plagues in the area is the desert locust, Schistocerca gregaria. Locust swarms are now thought to have developed on the Red Sea coastal plains of Eritrea, and the southern Red Sea coastal plains of Sudan, and have been reported in Saudi Arabia, south-east Egypt, and Yemen. Swarms may be threatening Morocco and the Sahel as factors including favourable breeding areas, prevailing wind and weather patterns push the increasing swarms west. 

New review
A recent publication on grasshoppers and locusts(2) provides a useful account of how they come to plague the Sahelian area of Africa. It describes the precarious living to be gained from pastoralism and settled farming in the area, the life cycle of locusts and grasshoppers, and how the process of gregarisation develops. The book provides detail on the more contentious issues:  How effective have chemical pesticides been in controlling outbreaks of locusts?  How effective have the regional organisations set up to monitor and control outbreaks been? How effective has donor funding been in developing long-term responses to locusts and grasshoppers, in areas that are often riven by wars?

The FAO Workshop —
Safer locust control
FAO organised a workshop(3) in Morocco in May to identify a short-term research programme within the next 2-3 years before more environmentally-friendly locust control methods are available.
    The workshop was directed towards locust-affected countries and regional locust control organisations, research scientists, industry, environmental organisations and donor agencies. The environmental organisations attending were The Pesticides Trust [now PAN UK], Greenpeace International, and WWF International. The full report will be available from FAO shortly; this report provides a short summary.

Present chemical pesticides
FAO’s approved currently acceptable formulations of pesticides includes pyrethroids, carbamates and organophosphates. Older and persistent organochlorine products such as dieldrin are no longer used, but though the replacements lack persistence, there remain concerns about non-target effects on ecosystems and the dangers to operator health.

New insecticides/acaricides
The newer generation of benzophenyl urea insect growth regulators (IGRs)—triflumuron, hexaflumuron and diflubenzuron—work by inhibiting chitin-synthesis in the juvenile hoppers. They are ingested after contact, and prevent the complete moult taking place. They may be effective against marching juvenile hopper bands, but are not effective against fully or nearly developed adults. They are relatively persistent, and may provide a short-term solution in due course.  
    Further operational trials are required, together with information on application methodology, dose rates, width of barriers, and intervals between barriers. The current argument is whether industry should pay for such trials (as FAO insists) or whether FAO or governments should pay (as industry would prefer).

Fungal pathogens
Work from the UK-based CABI(4) has demonstrated the feasibility of using fungal pathogens such as Metarhizium spp. and Beauvaria spp. for locust control. Ultra low volume formulations are being developed that are stable and effective in the climatic conditions under which they are likely to be used. These can be made locally. Non-target safety has to be assured and the prospect of populations developing resistance to the pathogen discounted. One other concern is that should a such a biopesticide reach the market, it may never achieve acceptance because countries cannot yet agree on the appropriate biosafety standards for release.

Other control methods
Trials are underway on pheromones and anti-feedants but are not advanced.

Locust-affected countries
Representatives from Morocco, Algeria, Saudi Arabia, Yemen, Mauritania, and the regional organisation OCLALAV (the French Joint Locust and Bird Control Organisation) made statements to the workshop stressing the importance of environmental protection in locust control and the need to fund locally appropriate ecological research.
    Many expressed great concern about the continuing existence of stocks of obsolete pesticides that had previously been donated for locust control. Worryingly, there were suggestions that part of these stocks be transferred to other countries, under FAO co-ordination, to be used in place of the purchase of newer pesticides.

Donor agencies
 A number of donor agencies attended, including that of France, which has been supporting field research in IGRs, and has established a research programme on early detection and warning. The Netherlands has funded research in remote sensing, training, and environmental research. GTZ (Germany) is engaged in field trials with IGRs as well as contributing to assist in the disposal of obsolete stocks. USAID is also funding disposal projects and promoting preventive control. The International Fund for Agricultural Development IFAD is also funding locust control.

Recommendations
The workshop agreed the need for preventive control programmes, and recommended that appropriate data collection systems be developed, including ground survey methods and novel detection techniques related to vegetation and meteorology; staff training be improved; and national and regional research be improved.
    Stocks of obsolete pesticides remain a problem. To avoid future build-up, it was suggested that a pesticide bank be established in producer countries so that appropriate chemicals in appropriate quantities were available to send to locust-affected areas if needed.  Industry argued this would help to reduce the dangers of over-stocking and disposal in Third World countries. However it is doubtful if this proposal will attract support or funding.
    Environmental recommendations included the need to establish the effects of pesticides on beneficial organisms; the need to understand desert ecosystems, and to train scientists from locust-affected countries; the need to introduce risk assessment procedures for environmental evaluation of locust control measures; and the need to assess the effects of IGRs in aquatic and soil ecosystems.
    In terms of application technology, an airborne system to detect and demarcate hopper bands is needed; further research is needed to develop radar or detection systems linked to satellite Global Positioning Systems, and methods of recording treatment. Practical manuals and courses are required for calibration of equipment and spray  application.
    Field trials were strongly recommended for promising pathogens and growth inhibitors and repellents, together with the need to produce guidelines for toxicological standards to be met by such botanical insecticides.

Environmental concerns/other issues
Locusts and grasshoppers
Many delegates were concerned about the focus on desert locusts, and considered that grasshoppers were just as serious a problem. Grasshoppers cause damage to crops on a recurrent, seasonal basis, without the drama and crisis that accompanies a locust infestation. Grasshopper control lends itself more to farmer centered activities, and has greater potential for incorporation within IPM strategies.

Longer-term solutions
The Workshop set out to examine the shorter term research priorities. However, the longer-term strategy for locust control was not clear. The environmental groups in particular wanted an examination of the cost-effectiveness of chemical controls; an investigation into other solutions, including food and farmer support; and an evaluation of regional,  as opposed to local,  crop losses. The background paper prepared by Greenpeace International and The Pesticides Trust(5) echoed concerns of the US OTA Report. Without an examination of the longer-term goals of locust control, and consideration of alternative means of achieving the same end, the use of chemicals threatens to become an end in itself.

Politics of locust control
The politics of locust control is a difficult business. FAO can only coordinate agreed control efforts. Governments making  pesticide donations have their own priorities. Regional organisations such as OCLALAV and DLCO-EA (Desert Locust Control Organisation for East Africa) have been established, but there were criticisms on the cost and effectiveness of regional organisations. Equally, donor countries have, wittingly or otherwise contributed to the problem by short-term funding, so that in times of remission, the regional organisations and infrastructure have been neglected. At the workshop there appeared to be no consensus on the next moves, so donors may decide in default of political decisions.
    The recommendations of the Workshop will be forwarded to the Scientific Advisory Committee of the Consultative Group for Locust Research; but environmental groups and many delegates felt there was no clear political process to drive locust control. The matter will not be brought before the forthcoming FAO Biennial Conference in Rome in November and it is not clear how any policy will be either developed or implemented.

Conclusions
The Workshop resulted in a sensible wish-list of recommendations for short-term research in desert locust control. Two conclusions emerge.
    Firstly, whilst welcoming the opportunity to participate, environmental groups felt that this could have been achieved with less time and money—especially as the real decisions are likely to be taken by a small group of donor agencies meeting in the Netherlands in December this year, when the issues of what projects are feasible and what gets funded will be decided. Secondly, the long-term problems of locust control strategy remain with us. Thirdly, in contrast with the position a few years ago, the tenor of the arguments about locust control have significantly altered. The environment is high on the agenda. As one of the German delegates put it, “Now when you mention the environment, no one goes crazy.”

References:
1. US OTA, A Plague of Locusts—Special Report. OTA, US Government Printing Office, Washington, 1990.
2. Rowley, John with Bennett, Olivia, Grasshoppers and Locusts: The Plague of the Sahel, Panos Dossier 5, The Panos Institute, London, 1993, 120pp., £7.95.
3. FAO International Workshop on Research and Planning for Desert Locust Control, Marrakesh, Morocco, 24-26 May 1993.
4. Prior, Chris, ‘Biocontrol of Locusts and Grasshoppers: A Recent Research Programme’, Pesticides News 19,  March 1993.
5. The Need for a New Approach to Locust Control, Greenpeace International, Amsterdam/The Pesticides Trust [now PAN UK], London, 1993, 11pp.

[This article first appeared in Pesticides News No.21, September 1993, pages 8-9]