The seeds of past Irish World Cup disappointment have often been sown with worrying warm-up form, and while the Six Nations Grand Slam winners were their relentless best in the first half, they took their foot off the gas in the second.
The world's top-ranked team will also be sweating over back-row Jack Conan, who watched on in a plastic 'moon' boot following a first-half injury.
Italy fielded a stronger team than the experimental outfit beaten 25-13 by Scotland last week and took an early 3-0 but Kieran Crowley's men were totally outmatched early on. They too lost Marco Riccioni and a tearful Tommaso Menoncello to concerning-looking injuries.
Ireland, who also started some players assured of their place on the plane to France, wrestled control of the game with a Dave Kilcoyne try before Caelan Doris and Stuart McCloskey added a try apiece while Danilo Fiscettoi was in the sin bin.
Player of the match Doris, who usually operates for Ireland at number eight, put in a superb first-half shift at openside flanker, where he will likely provide cover in France should anything happen to world player of the year Josh van der Flier.
With Farrell looking set to prioritise versatility in his final squad, Ryan Baird also equipped himself well at blindside flanker, having previously featured for Ireland at lock, while utility man Jimmy O'Brien was again very reliable at fullback.
Munster youngster Jack Crowley also had a solid game at flyhalf, with captain Johnny Sexton suspended for all three warm-up games, as did 22-year-old Joe McCarthy at lock.
However, Farrell's men were much sloppier in the second half, which featured debuts off the bench for Tom Stewart, Ciaran Frawley and Calvin Nash, allowing Italy replacement Lorenzo Pani cut the deficit with his first international try.
Cian Healy, who came on to become Ireland's joint third most capped player, marked his 124th appearance with a try before Menoncello got Italy's second and Doris added a second of his own to make sure of an 11th successive win for his team.
They should face a sterner test in two weeks' time against England, the same day Italy play Romania.
