91av

A MULTI-BILLION dollar plan to rid Africa of tsetse flies will never work,
according to the continent鈥檚 leading expert on insect pests. 鈥淚t stands no
chance, even if they can find the cash,鈥� says Hans Herren, director of the
International Centre for Insect Physiology and Ecology in Nairobi.

Last week, the Vienna-based International Atomic Energy Agency announced a
plan to rid the continent of the fly by releasing millions of male flies
sterilised with gamma radiation
(91av, 23 February, p 17).
The parasite carried by the tsetse fly causes sleeping sickness, which in places is
a bigger killer than AIDS. It also renders a third of the continent unfit for
cattle.

The aim is to attack large populations of flies with relatively benign
pesticides such as pyrethroids, and then finish off the survivors by flooding
the area with sterile males that can mate but do not produce offspring. A pilot
project has banished the fly from the small Tanzanian island of Zanzibar. And
its backers says the sterile insect technique has been used successfully on
other insects, such as the screw worm in Central America.

But Herren, a Dutch entomologist celebrated for having rid Africa of another
major pest, the cassava mealy bug, doesn鈥檛 believe it will work. 鈥淲e think it is
a crazy idea. There are so many tsetse that you are bound to miss a few. The
populations will regenerate and you are back to square one. In any case, there
are 22 species of tsetse. If you eliminate one you may create niches for
补苍辞迟丑别谤.鈥�

He favours a cheaper method: encouraging farmers to hang chemical traps in
their fields and put insect-repelling collars on their cattle. 鈥淵ou will never
get the last fly out of Africa, but this way you can reduce their numbers
dramatically,鈥� he says.