Naples, March 26 - Producers of buffalo mozzarella under the Protected Denomination of Origin (DOP) appellation on Tuesday threatened to halt activities as of July 1 in protest over new rules governing production. Specifically members of the consortium for the protection of buffalo mozzarella DOP are unhappy about the requirement to create separate premises for the production of DOP mozzarella using buffalo milk and for other cheeses made using ordinary cow's milk. Producers are obliged to make the change by July 1. In a letter addressed to the agriculture ministry and other interested parties consortium members explain that significant investments would be needed in order to continue operating ''within the rules''. Farmers' assciations have instead spoken out in support of the change.