But it was the Welsh side who took an early lead, full-back Prydie knocking over after just two minutes.
But after some early pressure the home side crossed after nine minutes, Gori catching Alberto Scarbi's kick ahead to touch down.
Alberto Di Bernardo was on target with the conversion, and three minutes later the fly-half dispatched a penalty to make it 10-3.
Prydie narrowed the gap to four but Treviso had soon crossed again - Loamanu crossing the whitewash after good link-up work between di Bernardo and lock Cornelius van Zyl.
Di Bernardo missed the conversion to leave the score 15-6 on 25 minutes.
After a scoreless ten minutes Harries saw yellow with half-time approaching - and Treviso made the most of their numerical advantage.
Half way into the Dragons wing's time on the sidelines Italy's McClean grabbed Treviso's third try of the afternoon to make it 20-6 - as it remained at the interval as di Bernardo failed to find target with the conversion.
And after the break the home side picked up where they left off with Harries still in the bin, Loamanu grabbing his second try of the match on 42 minutes to secure the bonus point.
Prydie moved the visitors into double figures ten minutes later, grabbing Dragons' first try of the afternoon and converting himself to bring the score back to 27-13.
But any chances the Welsh side had of a comeback came to an end just after the hour mark when Harries, who had been sin-binned in the first half, rounded off a miserable afternoon as he was sent off.
Treviso once again capitalised on the numerical advantage and grabbed a fifth try, scrum-half Boates going over to seal a well-deserved 32-13 victory.
|Benetton Treviso Score Card|
|Alberto di Bernardo||2||1||7|
|Newport Gwent Dragons Score Card|