AFRICA: Fruit farmers to use ants for pest control

Three universities will spearhead the training of African fruit and nut growers to use weaver ants to control pests. Farmers incur huge financial losses as their crops are attacked by insects and this form of pest control will reduce losses while opening doors to world organic food markets.

Scientists from the University of Aarhus in Denmark will work with researchers from Sokoine University of Agriculture in Tanzania and the University of Abomey-Calavi in Benin on the project, starting this month.

The ants used to control pests live in the canopies of a variety of plantation trees. If managed properly, a straightforward operation, they build up high densities of ants, said Joachim Offenberg from Aarhus University's centre for tropical ecosystem research.

Offenberg explained that as the ants feed on all kinds of insects in the trees, they destroy or deter a range of different insect pests - and in some cases even mammals such as fruit bats because they also attack large enemies while protecting their territory against intruders.

"We all know this behaviour by ants, as people are also chased away by ants if they stay too close to an ant nest," Offenberg told University World News.

Associate Professor Mogens Gissel Nielsen, a biologist and project manager at Aarhus, said a breakthrough last spring made it possible for the university's researchers to produce ant colonies by catching fertilised queen ants just after swarming.

Nielsen said that to avoid too much impact on the natural fauna, the researchers chose to 'rear' colonies of ants that could be released directly into the plantations, rather than collect colonies established in the surrounding countryside. He said this new knowledge would be used to set up 'ant farms' as part of the project.

Once the Aarhus researchers have transferred their expertise to farmers, the free pest control - an improved method of cultivation used by Chinese farmers for centuries - needs only simple, inexpensive inputs such as rope to link trees together and cutters to prune trees between different ant colonies.

Because no pesticides are used, farmers can get their production certified as organic and gain access to lucrative western markets where demand is high and increasing, said Offenberg. The edible weaver ants are rich in protein and can also be harvested for consumption when their numbers grow.

The Danish International Development Agency, DANIDA, has granted EUR 1.3 million (US$1.7 million) to develop and adapt the pest control method using ants.

The two African universities were chosen for their high standards and suitability. They have leading researchers who have carried out preliminary work with weaver ants and can offer high quality PhD programmes, Offenberg said.

"Our partners in both countries have done work with weaver ant biocontrol but have not yet tried to breed live colonies for farmers. Our expertise on this subject will be transferred to Africa during the project," he said.

Through its department of crop science and production, Sokoine University of Agriculture (SUA) has the capacity to train students at PhD level in various fields of entomology and pest management, and is well prepared to undertake this project, said Dr Mwatawala Maulid, the SUA project leader.

Maulid said they had been conducting research on fruit flies since 2004 so the project on weaver ants would fit well with their current programmes. Available facilities could be shared between projects.

She told University World News that researchers were optimistic the project would be sustainable in areas where weaver ants would establish themselves well. But there was still much work to do to educate farmers on conservation of weaver ant populations once they were established.

Studies for Benin and Tanzania have estimated the value of increased production of mangos and cashews at more than US$300million after eliminating fruit fly through ant pest control.