Farmers in Benin harvest fruit of far higher quality if they allow weaver ants (Oecophylla longinoda) to infest their mango (Mangifera indica) trees. Scientists at the CGIAR’s Inland Valley Consortium noticed that fruit-fly damage was lower in trees where weaver ants were abundant. So they arranged to exclude ants from trees on six plantations. The results were very encouraging. ((Paul Van Mele; Jean-François Vayssières; Esther Van Tellingen; Jan Vrolijks. Effects of an African Weaver Ant, Oecophylla longinoda, in Controlling Mango Fruit Flies (Diptera: Tephritidae) in Benin. Journal of Economic Entomology 2007, vol. 100, no. 3, pp. 695 – 701.)) Farmers who tolerated the ants can manage without pesticides and are able to sell their mangoes into the lucrative European organic market. The scientists reckon it takes just a day to teach farmers about the benefits of weaver ants, and are planning to take their ideas to East Africa and Asia.
There is just one downside. The ants bite. But that can be avoided by harvesting the fruit with poles instead of by climbing the trees. ((There are further write-ups at Scidev.net and The Economist.))