Food exports and grants for farmers could be affected by industrial action that is set to commence at the Department of Agriculture on Monday.
The dispute, involving around 600 lower-paid technical staff belonging to IMPACT, centres on promotions to the assistant principal grade.
The union argues that its members have been refused the opportunity to compete for assistant principal posts that have been approved for filling.
The technical inspectors are responsible for ensuring food safety and compliance with regulations on production, sale and certification of agricultural produce, including live animals.
They carry out inspections of farms, meat factories, dairy processors, marts, mills, laboratories and other facilities.
They are also involved in administering farm development and improvement schemes.
IMPACT argues that if the posts were filled by its members, it would deliver cost savings of up to €45 per hour or 55% by reducing the use of higher-paid veterinary contractors.
The union says that initially the action will be aimed at causing "administrative inconvenience".
Technical staff will refuse to cooperate with proposed transfers of staff and will only communicate through agreed traditional reporting relationships.
However, it warns that the row could escalate by late next month to more disruptive action if the dispute is not resolved - and could delay grant payments to farmers, as well as the processing and export of cattle and other agricultural products.