The agriculture minister said there were now 16 confirmed outbreaks of ash dieback in Northern Ireland, on 4 December 2012.
Michelle O'Neill said the disease had been found in counties Antrim, Down, Londonderry and Tyrone and 8,700 plants had been destroyed.
Two cases of the disease had also been detected in trade premises.
The minister said ash dieback had been found to come from four different sources, all of which were linked to imports from continental Europe.
Mrs O'Neill said her department aimed to check 1,000 sites, and had so far completed over 200 inspections.
The minister also replied to questions about the common agricultural policy, and the tackling rural poverty and rural isolation strategy.
Culture Minister Caral Ni Chuilin told members that 6,000 people had already applied to volunteer for the 2013 World Police and Fire Games
She said violent scenes outside Belfast City Hall the night before had done nothing to promote "the friendliest games ever".
Jim Allister of the TUV wanted to know if a member of the Royal family would attend the games, and whether an invitation had been issued .
"I haven't received any such invitation," Ms Ni Chuilin replied.
Representatives of the Assembly Commission then answered questions on subjects ranging from visits to Parliament Buildings by Irish language schools, flying the Union flag on Ulster Day, and prompt payments to contractors.