Taoiseach Brian Cowen's security team had to fend off hostile opponents of the Lisbon Treaty during a walkabout at the ploughing championships.
One reporter was slightly injured during a scuffle.
Mr Cowen's entourage was surrounded by members of Sinn Féin who chanted: "No to Lisbon."
Fianna Fáil support has plummeted among the farming community, according to a Red C poll published in the Farmers Journal today.