The Millennium Stadium Manager, Gerry Toms, confirmed that a decision has been made to replace the pitch to avoid the consequences of grass and root erosion which could take place before the remaining Invesco Perpetual Autumn series internationals.
The games against Argentina on Saturday 21 November and Australia on Saturday 28 November will now be played on new turf which will be delivered from County Turf in Lincolnshire and laid over the weekend.
The new grass surface will be laid on the existing pallet and soil foundation will consist of 1.2metre by 15 metre lengths of turf which will have been maturing and developing root growth for 18 months.
Bibionidae fly infestation was discovered when the independent experts were called in as a precaution to check the pitch after excessive rainfall had affected the surface prior to the international match against New Zealand.
Advice from experts has indicated that quality of the pitch at its current level cannot be guaranteed while the Bibiondae fly infestation is still active.
In the ten year history of the Stadium more than 25 pitches have been laid and this is the second occasion when an infestation has resulted in a decision to immediately change the pitch.
Millennium Stadium Manager, Gerry Toms, said: "We have decided to avoid any risk of the infestation causing further erosion over the weeks ahead by deciding to replace the surface now.
"Obviously our major concern was how much damage might take place between now and the Australia match which will take place at the end of November.
"By installing a brand new surface we effectively remove any question mark over the stability of the surface because the turf delivered will have healthy root and grass growth.
"The important issue is that we have carried out the correct checks and acted decisively on the information before us.
"The pitch tonight was not to the standard we require which, combined with the unknown factor of the potential erosion over the next two weeks has prompted us to act now instead of waiting for any further assessments in the days ahead."
The pitch was tested by the STRI, Sports Turf Research Institute and following their initial findings independent experts were consulted separately to confirm the condition of the pitch and advise on treatment or replacement options.
Mr Toms explained that the WRU had been advised that the Bibiondae fly infestation cannot be treated effectively to destroy the microscopic insects.
Agronomist Mr John Lockyer, one of the independent experts called in separately to advise on the condition of the pitch, said: "We have confirmed the presence of this infestation and I agree with the decision to take positive action now to replace the surface.
The insects which consume the grass thatch and root material can multiply during the current weather conditions.
In October 2008 Root Knot Nematodes which causes gradual deterioration of the grass quality, was discovered in the Millennium Stadium pitch and the turf was replaced.