Tanzania has banned Kenyan dealers from buying onions at the farm gate in the Lake Eyasi basin. The ban which was imposed by local authorities also blocks farmers from signing any contract for farm gate onion sales but demands that they take their onions to Mangola market. Lake Eyasi division executive officer Laanyuni ole Supuk told The EastAfrican that the ban is effective July 1. According to Mr Supuk, Kenyan traders are also required to pass through immigration department in Arusha and Karatu before going to Mangola market. Legal action will be taken against any dealer or grower who contravenes the ban, he said. Onion buyers from Kenya are reported to have formed a cartel that ensures farm gate buying prices of local onions are kept low. Mangola Onions Sacco secretary general Ramadhan Sunuku said Kenyan onion traders have formed a tight network complete with spying agents in a bid to manipulate farmers. Mr Sunuku said that as soon as the local farmers harvest their crop, the Kenyan buyers alert one another. They control the onion market as they set the price at their will, he said adding that they normally offer them the lowest price possible irrespective of the quality of the onions. The onion benchmark price was supposed to be $114 per bag in the local markets, but the Kenyan dealers are only offering between $46 and $50 per bag. The onion is a leading cash crop in the Lake Eyasi fertile delta of Karatu district, 200km west of Arusha, earning farmers a $2.7 million per annum. The 1,000 sq km basin accounts for third of East Africas Bombay Red and Red Crole onions. Lake Eyasi basin onion yields have swelled from 24,160 tonnes in 2003 to some 30,900 and 43,000 tonnes in 2004 and 2005 respectively. In 2006, the basin produced 75,600 tonnes. In 2007 the production rose to 86,464 tonnes, while 97,328 and 90,789 tonnes were produced in 2008 and 2009 respectively.