A special aid of 2 500 ECU per hectare shall be granted for areas under, essentially, bitter hop varieties, on terms to be set by the procedure indicated in paragraph 6, to producer groups recognized under Regulation (EEC) No 1696/71 the members of which undertake to implement before 31 December 1990 a plan for conversion to aromatic or super-alpha type varieties. This special aid shall be given for a total area of no more than 800 hectares in each Member State concerned.