Behind the receptionist's desk the 'Pest Outbreak Reports' chart is blank. A tangle of circuits and telephone wires spills into a hole in the floor by the director's office.

The library is full, but most of the publications hail from the colonial era. Even the information leaflet was printed in 1961 and refers to Zambia as Northern Rhodesia. But the special 'IRL' number plates on the cars outside its concrete headquarters betray the unique status of the International Red Locust Control Organisation (IRLCO).

According to John Bahana, its scientific officer, this once-great bureau remains the front line against a menace that even now could bring agricultural chaos to a dozen countries.

In the 1940s, red locusts were headline news. A 15-year plague had swamped almost half a continent, and Belgian and British scientists worked overtime to identify its Source.

Under the patronage of Boris Uvarov, the Russian father of locust science, a large complex was established in Abercorn (Mbala) in 1949 on the southern shores of Lake Tanganyika, close to the breeding centre of the ravenous hoppers.

In its heyday, hundreds of employees were on constant alert. Dusty press reports from the 1950s sport lurid tales of the 'locust menace', the dreaded 'eighth plague', that - if unchecked - could raze thousands of hectares of farmland. Fear of the red destroyer had almost communist over-tones.

On Saturday, as it prepares to celebrate its 50th birthday with an international symposium, the media attention has all but disappeared. Ndola, the Zambian copperbelt town where IRLCO relocated 15 years ago, is a shadow of its one-time opulence. Last year the organisation had to cut its 56 staff to 27 and its budget has dwindled from $1.8m to $1.1m.

Dr Bahana warns that without the body's three aircraft and monitoring activities the red menace could all too easily resurface.

As recently as 1996, Mozambique (where vigilance had waned) faced an outbreak of more than 100 swarms - with one comprising 180m locusts.

IRLCO responded swiftly, attacking the pest with the chemical fenitrothion in areas where it would have the least ecological impact. A plague was averted.

Since then things have been quieter. The vicious desert locust, which is monitored from Addis Ababa, appears to have surpassed its red cousin in destructiveness.

But that is no reason to lower Africa's guard. There is a story of a European man who threw newspapers out of a train to keep away the elephants. The fact that there were no elephants, he claimed, simply proved the effectiveness of his behaviour. So with IRLCO.

'This organisation is like an insurance scheme,' says Dr Bahana. 'Farmers may not see the locusts, but that doesn't mean the threat is over. Danger is always lurking in the background.'