Few people like ants—they bite and overrun kitchen counters. But in Vietnam, thousands of farmers have turned to weaver ants to help them grow their cashews. That's because in 2008 researchers showed that these reddish brown insects are so much more effective and cheaper than chemical sprays at eating or deterring pests that the farmers' net income jumped 71%. Curious whether weaver ants might be effective alternatives to pesticides in other situations and eager to see whether biocontrol methods did work, researchers have now combed the literature for relevant research. When ants came, crop yields often improved, the team concludes online today in the Journal of Applied Ecology. And the insects proved superior to other pest control methods in four of the six studies that evaluated cost-effectiveness. Calling this "the best documented case of efficient biocontrol in open agricultural systems," the researchers think more farmers should make use of ant control. The idea of using weaver ants is not new, they point out. About 1700 years ago, Chinese farmers could buy ants on the market to release in citrus groves, a practice long forgotten with the invention of chemical pesticides. But now, two European companies are considering how to provide weaver ant nests to farmers, and a Danish aid project is helping to establish ant nurseries in Africa so as to provide mature colonies to farmers interested in trying out these six-legged pest controllers. Given that there are 13,000 ant species in the world, the potential may be limitless, the researchers note.