The Australian winger crossed twice in the first half while Ludovico Nitoglia, Alessandro Zanni, and replacements Robert Barbieri, Paul Derbyshire and Tobias Botes also scored tries as Treviso made it four wins in a row.

Tonderai Chavhanga scored two tries, his first in the RaboDirect PRO12 since arriving last month from South Africa while Steffan Jones also scored a try for the visitors.

Treviso welcomed back several World Cup stars but it was the players who had helped them to their first league wins away from Italian soil against Glasgow and Ulster who proved the difference with Kris Burton contributing 13 points with the boot.

It was the home side who made the better start as Azzurri flanker Zanni scored the first try of the game after just five minutes.

Burton added the extras and he was on target again three minutes later after Williams scored his first of the afternoon.

Williams had his second on the quarter hour, with Burton's conversion giving Treviso a comfortable 21-0 lead.

The Dragons were handed another blow as winger Mike Poole was forced off midway through the half, but replacement Jason Tovey and Burton exchanged penalties as Treviso led 24-3 at the break.

South African international Chavhanga got only his second try in Dragons colours immediately after the break, but any hopes of a comeback were killed off five minutes later as Nitoglia sealed Treviso's first-ever four-try bonus point.

Burton's conversion made it 31-10, and the Italians put the Dragons to the sword with three tries in five minutes to reach the 50-point mark.

First Botes crossed with 15 minutes to go, followed three minutes later by Barbieri, and finally back row Derbyshire scored Treviso's seventh with ten minutes remaining.

The Dragons did manage to show some fight as Chavhanga scored his second before Jones crossed with three minutes remaining, Tovey converting on both occasions.

But it was far too little too late as Franco Smith's side continued their charge up the table to move provisionally into the play-off places.