Locust upsurge allows environmentally safe control to be tested  

An effective biological control for desert locusts has been developed by a research programme LUBILOSA led by CABI Bioscience. Brian Pettit and Nina Jenkins report on the recent testing of Green Muscle® and prospects for widescale future use.

Locust in cereal crop. Photo: CABI Bioscience

The recent upsurge of desert locusts (Schistocerca gregaria) in West Africa has initiated a number of large scale emergency control operations across the Sahel region. About 880,000 ha were treated from the air and on the ground in West and Northwest Africa during December 2004. The total area treated since the beginning of the upsurge (October 2003) has now reached 12 million ha, according to United Nations Food and Agriculture Organisation’s (FAO) latest Desert Locust bulletin. As reported in the last edition of Pesticides News (No. 66), areas hit by desert locust swarms suffer devastating crop losses within hours of the arrival of a swarm with crop protection almost impossible once a swarm has landed. Preventative control is the preferred method. The FAO and the majority of countries in locust affected areas conduct regular locust monitoring and control local outbreaks. Upsurges only occur following periods of relatively high rainfall, such as that which occurred in the Sahel during the summer of 2003. This was followed by a short period of heavy rains in October, leading to perfect breeding conditions and triggering the latest upsurge in West Africa. Currently, all control operations are conducted with chemical insecticides. These must be approved for use against locusts by the FAO pesticides referee group and registered in the country of intended use. Although persistent organochlorines are no longer used for locust control, there is still concern over the environmental and health effects of the more commonly used organophosphates. Issues also remain over the disposal of obsolete stock from previous control campaigns. 
    The last full-scale locust plague occurred between 1986 and 1989 and required more than US$300 million and some 1.5 million litres of insecticide to bring under control. As a result of this and the concerns over the environmental impact and effects on human health, the international community initiated the development of alternative control methods. In 1989, a consortium of donors including the governments of Switzerland, the Netherlands, the United Kingdom and Canada funded an international collaborative research programme named LUBILOSA (Lutte Biologique contre les Locustes et les Sauteriaux). The aim of the programme was to develop a biological alternative for locust and grasshopper control. LUBILOSA was led by CABI Bioscience, in collaboration with the International Institute of Tropical Agriculture, Imperial College, AGRHYMET-CILSS (Centre Régional de Formation et d’Application en Agrométéorologie et Hydrologie Opérationnelle – Comité permanent Inter-états de Lutte contre Secheresse dans le Sahel) and a number of National Programmes in Sahelian countries. The programme ran for a period of 13 years during which the scientific team developed Green Muscle®, a mycopesticide based on an African strain of the fungus Metarhizium anisopliae var acridum. The fungus, is specific to species of short-horned grasshoppers (Acridoidea and Pyrgomorphoidea), including the desert locust, and is widely distributed in Africa.
    Green Muscle is applied as an oil suspension, can be sprayed using standard ultra low volume spinning disk spray equipment and has a long shelf life (more than five years under refrigeration and approximately one year at 30oC). Its efficacy has been demonstrated in many field trials on a range of locust and grasshopper species carried out by the programme and its collaborators over the past ten years, including aerial application at an operational scale. Efficacy studies were accompanied by environmental impact studies which revealed no significant impacts of the biopesticide on non target invertebrates.
    To support the use of Green Muscle, ecological studies were conducted to elucidate the effects of temperature and locust thermoregulatory behaviour on performance of the pathogen. This understanding of the host pathogen interaction spurred the development of a GIS-based model that predicts the variability in performance of the biopesticide in time and space, based on measures of ambient temperature. This enables locust control operators to use the biopesticide with confidence where temperature conditions are suitable and to employ chemical control in areas where environmental conditions would make control with the pathogen unacceptably slow. However, further testing and development are still required to validate the model for desert locusts, an opportunity that has not been available until now.
    FAO is the primary purchaser of locust chemical control products, particularly in upsurge situations, but has shown interest in employing alternative (non-chemical) controls where available, providing they are effective. FAO has purchased Green Muscle for trials against red locust in Tanzania and Sahelian grasshoppers in Niger and Mauritania. But until now, the opportunity to conduct large scale trials on desert locust has not been possible. The current upsurge now provides the opportunity for such trials and for Green Muscle to become an established product for preventative locust control.
    Funding from the International Fund for Agricultural Development (IFAD) was granted to FAO in December 2004 for use in the investigation of alternatives to chemical locust control. Operational applications of Green Muscle and the insect pheromone PAN (phenyacetonitrile) will be made in early 2005 over 2000 ha as part of standard locust control operations. This will be the first large scale trial on desert locusts. Furthermore a trial will be conducted using PAN in combination with Green Muscle. It is anticipated that PAN will enable the field dose rate for Green Muscle to be reduced from 50 g/ha to 12.5 g/ha, thus reducing the cost of Green Muscle to a level comparable with chemicals. Furthermore, the greater persistence of control with Green Muscle, and consequently reduced requirement for repeat application, may well bring down the total costs to below that for chemicals, without the costs and dangers of dealing with the safe disposal of surplus chemicals and contaminated empty containers.
    Clearly to have any significant impact Green Muscle needed to be produced on an industrial scale. With the agreement of the donor consortium, Green Muscle was to be licensed to two manufacturing companies with a presence in the region. Biological Control Products (Pty) Ltd (BCP), a small South African company was granted a geographically exclusive license for the production and marketing of Green Muscle in 1997. Investing in new production equipment, it is able to supply current levels of demand for Green Muscle trials, and it has registered Green Muscle in South Africa, Zambia, Namibia, Tanzania, Mozambique and Sudan.
    A second manufacturer was identified for West Africa, but unfortunately it did not prove possible to produce Green Muscle to specification at their existing European production plant. Nevertheless, in anticipation the LUBILOSA registration dossier was submitted to CILSS, and Green Muscle has been granted a temporary sales license (AVP) from the Comité Sahelien des Pesticides. Fortunately, the original LUBILOSA pilot production facilities at IITA, Benin have continued to be available to produce Green Muscle to contribute towards demand in West Africa.
    The Pesticides Referee Group of FAO has recommended Green Muscle for use in environmentally sensitive areas. So why has this ecologically friendly and well tested product not had any significant impact on the ground? It is not purely down to cost, nor is it entirely down to the overwhelming unbalanced commercial power of the agrochemical giants. It is also not just because Green Muscle is an innovative product going through all the expected commissioning teething problems. 
    There are lessons to be learned from the introduction of a similar product (different strain of Metarhizium effective against a different species of locust) Green Guard® in Australia, itself a product developed with the assistance of the LUBILOSA programme. Here the guaranteed uptake of the product by the Australian Plague Locust Commission gave the manufacturer confidence to invest more heavily in manufacturing plant capacity. This has meant that meaningful supplies of Green Guard® were available in Australia for emergency situations.
    In the current African upsurge the agri-giants have vast stockpiles of chemicals ready for use. Small biopesticide manufacturers, on the other hand, lack both the financial and logistical resources to support building up any significant stocks. Indeed in the light of the spasmodic nature of locust outbreaks and consequent uncertainty of demand, they may well in any case choose not to do so. Therefore, it is not difficult to predict that only a limited amount of stock would be available for emergency situations.
    The benefits of Green Muscle are clear to all. To allow ecologically friendly pesticides to play the role that we need them to, funds have to be made available to allow adequate stocks to be available to meet emergency requirements.

Brian Pettit and Nina Jenkins – CABI Bioscience, Bakeham Lane, Egham, Surrey, TW20 9TY, www.cabi-bioscience.org/html/Biocontrol.htm

[This article first appeared in Pesticides News No. 67, March 2005, page 13-14]