Matthew Screech, Ross Wardle and Cory Hill all touched down for the Dragons but Treviso outdid the Welsh region by five tries to three.
And, without a win since edging past Glasgow Warriors 24-23 in February, Jones has called on his team to sharpen up their skills ahead of this season's final three RaboDirect PRO12 games.
"I wouldn't question our attitude but I would question our ability," he said.
"We had some positives but in the end we conceded five tries and that comes down to individual responsibility."
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