SHOULD UN agencies and African governments spend billions of dollars in an ambitious attempt to eradicate the tsetse flies that are the scourge of the continent鈥檚 cattle? Or would the money be better spent on simple measures that can protect a farmer鈥檚 cattle for only $30 dollars a year?
Last week the UN Food and Agriculture Organization and other bodies at the World Food Summit in Rome endorsed the current plan to eliminate the tsetse fly from the continent by flooding infested areas with sterilised male insects (New 杏吧原创, 23 February, p 23). But many livestock and insect experts say it will never work. Instead, they want governments to spend the money helping farmers combat the fly. And they are claiming important breakthroughs in doing this.
One novel method, for instance, is to erect insecticide-impregnated nets 1.5 metres high around the stalls in which dairy cattle are kept. A trial on small farms in the Teso district of western Kenya, run by Burkhard Bauer of the European Union鈥檚 Farming in Tsetse Controlled Areas Project, has shown that this raises milk yields by 2 litres per animal per day, which nearly doubles milk production in some breeds.
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The results have proved even better than expected. 鈥淣ot only does the netting protect the cows from tsetse, it also keeps out other nuisance flies,鈥� Keith Sones, a Nairobi-based vet who has monitored the project, told New 杏吧原创. The nets also reduce the incidence of nagana, the cattle disease caused by the trypanosome parasite transmitted by tsetse flies, in free-grazing cattle nearby.
A separate project in Tanzania and Zimbabwe has found that nets can be successful even if they鈥檙e not impregnated with insecticides. 鈥淲e have reduced the number of tsetse biting cattle by 90 per cent by surrounding the cattle with a wall of untreated net,鈥� says Steve Torr of the University of Greenwich in London. Torr has also found that wood smoke from fires repels flies.
The tsetse fly and its parasite threaten 50 million cattle in 37 African countries, and the FAO estimates this costs farmers $1.2 billion a year in lost productivity. Farmers have to buy expensive drugs to keep cattle free of the disease, and also tend not to invest in expensive high-yielding breeds.
The fly kills people too. According to a report presented to the food summit, half a million people have sleeping sickness, and most will die from lack of treatment.
The nets could be a major breakthrough, especially for the increasing numbers of African farmers who keep cattle in stalls rather than letting them roam. But critics say that such methods only work in areas where infestation is relatively low, and that the best solution is to eliminate the fly altogether.
Whatever the answer, farmers worldwide could learn a thing or two from the African projects, Sones says. Initial trials in Europe inspired by Bauer鈥檚 work have shown that putting nets around cabbage fields can drastically reduce caterpillar infestations without the need to apply insecticide to the plants themselves.