It is a natural alternative to pesticides. In Thailand (Southeast Asia), rice farmers are helped by hordes of ducks who come to clean their rice fields. After harvest, the ducks feed on worms and parasites which abound in the fields. In one week, 10,000 ducks can clean up 67 hectares of plantations. This use of ducks is an ancestral tradition in Southeast Asia. Thailand is the third-largest exporter of rice in the world, after India and Vietnam.