County Monaghan is facing its "most serious" outbreak of bird flu.
The warning comes from the IFA after a third case was detected in an egg-laying flock in the Oram area yesterday.
This follows two previous outbreaks at turkey and broiler farms close to Latton last month.
There is also a suspected outbreak in a flock just across the border in Northern Ireland.
Farmers are being reminded that increased biosecurity and hygiene is the only way to keep it out.
IFA Poultry Chair Andy Boylan says the impact is likely to be worse than the major detection in 2019.