Warriors recorded a first double over their capital rivals since campaign 2009/10, with Saturday's three-try romp at Murrayfield securing the oldest club trophy for the fourth time on the bounce.
Van der Merwe became Glasgow's leading try scorer in pro-league rugby with a double in the first leg, taking his tally to 22, one better than Thom Evans.
But now, with Italian cracks Treviso coming to Scotstoun on Friday night, the Warriors' Canadian wing says it is vital that Glasgow continue to build momentum.
He said: "To do the double over Edinburgh is not something that happens every year. I think that was only the second time in the last 10 years or so.
But what is absolutely vital is that we build on it.
"By winning home and away against Edinburgh we have put to bed a four-game losing run.
"We have climbed back into the play-off places and are very well placed to kick-on.
"However, if you want to be involved at the business end of the season, you need to take care of business at home and we need to beat Treviso on Friday, make no mistake."
The Scotstoun try king is expecting a very different game against the stubborn Italians.
He said: "Whereas Edinburgh play a fast, off-loading game and really use the width of Murrayfield well, we know that Treviso will be playing the traditional forwards dominated Italian game.
"So up front it is going to be tough.
"Our forwards have been playing really well as a unit and we are confident we will get the quality of ball in the backs to hurt them."