Better locust forecasting through technology

This battery-operated GPS device, used here in Madagascar, helps countries to keep track of locust sightings. (FAO/20510/A. Proto)

A swarm of desert locusts fly over a savanna in Senegal. (FAO/17140/M. de Montaigne)


A female desert locust in Mauritania about to lay an egg pod, containing about 100 eggs. (FAO/20599/K. Cressman)


The same technology that helps boaters and hikers get their bearings
in the great outdoors is assisting developing countries to control an age-old problem: plagues of the desert locust. Swarms of this flying insect can strip a field's vegetation in a few hours. Yet, keeping track of the desert locust is no easy task, considering they are found in 25 countries spanning 16 million square kilometres, from Mauritania in western Africa to India in the east. Now, the introduction of a global positioning system (GPS) and a portable computer is streamlining the process.

As part of its mandate to help countries better control the locust, FAO provides training on how to use these two devices. Locust survey officers use the GPS to pinpoint their location to within 10 metres and store the precise coordinates of the sites they visit. They then connect the GPS to a second device, a wallet-sized palmtop computer, which runs a custom-designed programme called eLocust. At day's end, they plug the computer into a high-frequency radio in their vehicle and transmit the crucial data to the national office through a modem powered by the cigarette lighter.

"Desert locust plagues can flare up suddenly," says locust officer Keith Cressman, "so the key to effective control is intervening early. This technology will help us to relay the data quickly and accurately."

Until now, survey teams collected data manually, filling out forms and sending them by fax or e-mail to the national office, and from there on to FAO headquarters. But that process is no match for the fast-moving locusts, which can cover more than 100 kms in a day.

The GPS is already being used in 18 countries and the palmtop computer in at least half a dozen. Both the GPS and palmtop work well, even in high temperatures and in sandstorms.

The last major outbreak of the desert locust hit between 1987 and 1989. Such is their voracity that a very small part of a swarm (or about one tonne of locusts) can consume as much food in a day as about 10 elephants or 2 500 people. When swarms strike just before harvest time, the impact can be crippling. By the time the 1987 plague ended, it had reached all 25 susceptible countries, causing devastating losses. Since then, there have been a few upsurges, but no plagues. "But that can change at any time," reminds Mr Cressman.

Locust survey teams are on the lookout for two signs. They watch for the conditions that favour reproduction, including moist sandy soil, some bare areas for egg laying and green vegetation providing food for young locusts. The team is also trained to detect changes in the insects themselves. Researchers originally thought that there were different species of desert locust, solitary ones and "gregarious" ones that joined together in swarms. But they now understand that a single species changes behaviour and colour over time: solitary locusts are brown, but turn pink when they join a group and yellow as they age. Locusts begin to swarm when sensors on their hind legs are stimulated by contact with large numbers of other locusts, triggering synchronized behaviour.

Once locusts are detected, pesticides keep their numbers in check. Locust control is generally carried out by the local Ministry of Agriculture, through national locust units. Regional organizations also offer assistance, and in times of a plague, the international community steps in. The speed of the new system should help FAO forecasters to warn neighbouring countries threatened by locust swarms. It should also permit a reduction in pesticide use, since outbreaks will be pinpointed more accurately.

Last but not least, it will lighten the load of the survey officer, who often makes a dozen visits in a day, checking conditions, looking for locusts and talking to nomads, villagers and farmers.

"The survey officer has the worst job of anyone," said Mr Cressman. "This should help a lot."

1 June 2001 

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